diff --git a/eo-phi-normalizer/app/Main.hs b/eo-phi-normalizer/app/Main.hs
index 74ce53474..b6a1ef66b 100644
--- a/eo-phi-normalizer/app/Main.hs
+++ b/eo-phi-normalizer/app/Main.hs
@@ -466,7 +466,7 @@ instance Show CLI'Exception where
     CouldNotParse{..} -> [fmt|An error occurred when parsing the input program:\n{message}|]
     CouldNotNormalize -> [fmt|Could not normalize the program.|]
     CouldNotMergeDependencies{..} -> message
-    Impossible{..} -> message
+    Impossible{..} -> [fmt|Impossible happened:\n{message}|]
 
 getFile :: Maybe FilePath -> IO (Maybe String)
 getFile = \case
diff --git a/eo-phi-normalizer/eo-phi-normalizer.cabal b/eo-phi-normalizer/eo-phi-normalizer.cabal
index 8dad4a0f0..11fec6313 100644
--- a/eo-phi-normalizer/eo-phi-normalizer.cabal
+++ b/eo-phi-normalizer/eo-phi-normalizer.cabal
@@ -394,6 +394,7 @@ extra-source-files:
     test/eo/phi/dataization.yaml
     test/eo/phi/from-eo/as-phi.yaml
     test/eo/phi/metrics.yaml
+    test/eo/phi/parser/expressions.yaml
     test/eo/phi/rewriting.yaml
     test/eo/phi/rules/new.yaml
     test/eo/phi/rules/streams.yaml
@@ -487,6 +488,7 @@ library
     , text
     , text-manipulate
     , unordered-containers
+    , validation-selective
     , with-utf8
     , yaml
   default-language: Haskell2010
@@ -538,6 +540,7 @@ executable eo-phi-normalizer
     , text
     , text-manipulate
     , unordered-containers
+    , validation-selective
     , with-utf8
     , yaml
   default-language: Haskell2010
@@ -619,6 +622,7 @@ test-suite doctests
     , text
     , text-manipulate
     , unordered-containers
+    , validation-selective
     , with-utf8
     , yaml
   default-language: Haskell2010
@@ -628,6 +632,7 @@ test-suite spec
   main-is: Main.hs
   other-modules:
       Language.EO.Phi.DataizeSpec
+      Language.EO.Phi.ParserSpec
       Language.EO.Phi.RewriteSpec
       Language.EO.PhiSpec
       Language.EO.Rules.PhiPaperSpec
@@ -679,6 +684,7 @@ test-suite spec
     , text
     , text-manipulate
     , unordered-containers
+    , validation-selective
     , with-utf8
     , yaml
   default-language: Haskell2010
diff --git a/eo-phi-normalizer/grammar/EO/Phi/Syntax.cf b/eo-phi-normalizer/grammar/EO/Phi/Syntax.cf
index 29c847fb3..e89066d2f 100644
--- a/eo-phi-normalizer/grammar/EO/Phi/Syntax.cf
+++ b/eo-phi-normalizer/grammar/EO/Phi/Syntax.cf
@@ -30,15 +30,15 @@ comment "//" ;
 comment "/*" "*/" ;
 
 token Bytes ({"--"} | ["0123456789ABCDEF"] ["0123456789ABCDEF"] {"-"} | ["0123456789ABCDEF"] ["0123456789ABCDEF"] ({"-"} ["0123456789ABCDEF"] ["0123456789ABCDEF"])+) ;
-token Function upper (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦"])* ;
-token LabelId  lower (char - [" \r\n\t,.|':;!?][}{)(⟧⟦"])* ;
+token Function upper (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦↦"])* ;
+token LabelId  lower (char - [" \r\n\t,.|':;!?][}{)(⟧⟦↦"])* ;
 token AlphaIndex ({"α0"} | {"α"} (digit - ["0"]) (digit)* ) ;
-token LabelMetaId {"!τ"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦"])* ;
-token TailMetaId {"!t"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦"])* ;
-token BindingsMetaId {"!B"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦"])* ;
-token ObjectMetaId {"!b"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦"])* ;
-token BytesMetaId {"!y"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦"])* ;
-token MetaFunctionName {"@"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦"])* ;
+token LabelMetaId {"!τ"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦↦"])* ;
+token TailMetaId {"!t"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦↦"])* ;
+token BindingsMetaId {"!B"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦↦"])* ;
+token ObjectMetaId {"!b"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦↦"])* ;
+token BytesMetaId {"!y"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦↦"])* ;
+token MetaFunctionName {"@"} (char - [" \r\n\t,.|':;!-?][}{)(⟧⟦↦"])* ;
 token IntegerSigned ('-'? digit+) ;
 token DoubleSigned ('-'? digit+ '.' digit+ ('e' '-'? digit+)?) ;
 token StringRaw '"' ((char - ["\"\\"]) | ('\\' ["\"\\tnrfu"]))* '"';
@@ -71,7 +71,7 @@ internal ConstFloat.    Object ::= Double;
 internal ConstInt.      Object ::= Integer;
 internal ConstString.   Object ::= String;
 
-AlphaBinding.       Binding ::= Attribute "↦" Object ;
+AlphaBinding.       Binding ::= AttributeSugar "↦" Object ;
 AlphaBindingSugar.  Binding ::= Object ;
 EmptyBinding.       Binding ::= Attribute "↦" "∅" ;
 DeltaBinding.       Binding ::= "Δ" "⤍" Bytes ;
@@ -81,14 +81,15 @@ MetaBindings.       Binding ::= BindingsMetaId ;
 MetaDeltaBinding.   Binding ::= "Δ" "⤍" BytesMetaId ;
 separator Binding "," ;
 
+AttributeNoSugar.   AttributeSugar ::= "#" Attribute;
+AttributeSugar.     AttributeSugar ::= "~" LabelId "(" [Attribute] ")";
+separator Attribute ",";
+
 Phi.    Attribute ::= "φ" ;   -- decoratee object
-PhiSugar. Attribute ::= "~" "φ" "(" [LabelId] ")";
 Rho.    Attribute ::= "ρ" ;   -- parent object
 Label.  Attribute ::= LabelId ;
 Alpha.  Attribute ::= AlphaIndex ;
 MetaAttr. Attribute ::= LabelMetaId ;
-AttrSugar. Attribute ::= "~" LabelId "(" [LabelId] ")";
-separator LabelId ",";
 
 -- Additional symbols used as attributes in the rules
 ObjectAttr. RuleAttribute ::= Attribute ;
diff --git a/eo-phi-normalizer/package.yaml b/eo-phi-normalizer/package.yaml
index 1c774444e..621a5bf77 100644
--- a/eo-phi-normalizer/package.yaml
+++ b/eo-phi-normalizer/package.yaml
@@ -97,6 +97,7 @@ dependencies:
   - megaparsec
   - parser-combinators
   - prettyprinter
+  - validation-selective
 
 default-extensions:
   - ImportQualifiedPost
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Dataize.hs b/eo-phi-normalizer/src/Language/EO/Phi/Dataize.hs
index c7f13c3db..b7f773abf 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Dataize.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Dataize.hs
@@ -108,7 +108,7 @@ dataizeStepChain mode obj@(Formation bs)
               ctx <- getContext
               return (ctx, AsObject obj')
   | DataizeAll <- mode
-  , Just (AlphaBinding Phi decoratee) <- listToMaybe [b | b@(AlphaBinding Phi _) <- bs]
+  , Just (AlphaBinding' Phi decoratee) <- listToMaybe [b | b@(AlphaBinding' Phi _) <- bs]
   , not hasEmpty = do
       let decoratee' = substThis obj decoratee
       logStep "Dataizing inside phi" (AsObject decoratee')
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Dataize/Atoms.hs b/eo-phi-normalizer/src/Language/EO/Phi/Dataize/Atoms.hs
index 5f240fc31..006c526c1 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Dataize/Atoms.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Dataize/Atoms.hs
@@ -163,11 +163,11 @@ knownAtomsList =
          where
           isPackage (LambdaBinding (Function "Package")) = True
           isPackage _ = False
-          dataizeBindingChain (AlphaBinding attr o) = do
+          dataizeBindingChain (AlphaBinding' attr o) = do
             ctx <- getContext
             let extendedContext = (extendContextWith obj ctx){currentAttr = attr}
             dataizationResult <- incLogLevel $ withContext extendedContext $ dataizeRecursivelyChain False o
-            return (AlphaBinding attr (either id (Formation . singleton . DeltaBinding) dataizationResult))
+            return (AlphaBinding' attr (either id (Formation . singleton . DeltaBinding) dataizationResult))
           dataizeBindingChain b = return b
         f name _otherwise = evaluateBuiltinFunChainUnknown name _otherwise
        in
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Dependencies.hs b/eo-phi-normalizer/src/Language/EO/Phi/Dependencies.hs
index 1b80716c6..5726f909c 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Dependencies.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Dependencies.hs
@@ -30,7 +30,8 @@ import Language.EO.Phi
 import Control.Monad (foldM)
 
 bindingAttr :: Binding -> Maybe Attribute
-bindingAttr (AlphaBinding a _) = Just a
+bindingAttr (AlphaBinding' a _) = Just a
+bindingAttr b@(AlphaBinding _ _) = errorExpectedDesugaredBinding b
 bindingAttr (EmptyBinding a) = Just a
 bindingAttr (DeltaBinding _) = Just (Alpha (AlphaIndex "Δ"))
 bindingAttr DeltaEmptyBinding = Just (Alpha (AlphaIndex "Δ"))
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Metrics/Collect.hs b/eo-phi-normalizer/src/Language/EO/Phi/Metrics/Collect.hs
index f155fa4e2..7bb3588f0 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Metrics/Collect.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Metrics/Collect.hs
@@ -29,6 +29,7 @@
 {-# LANGUAGE InstanceSigs #-}
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedLabels #-}
+{-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
@@ -43,6 +44,7 @@ import Data.Maybe (catMaybes)
 import Data.Traversable (forM)
 import Language.EO.Phi.Metrics.Data (BindingMetrics (..), BindingsByPathMetrics (..), MetricsCount, ObjectMetrics (..), Path, ProgramMetrics (..))
 import Language.EO.Phi.Rules.Common ()
+import Language.EO.Phi.Syntax (pattern AlphaBinding')
 import Language.EO.Phi.Syntax.Abs
 
 -- $setup
@@ -158,12 +160,12 @@ getThisObjectMetrics obj = execState (inspect obj) mempty
 
 -- | Get an object by a path within a given object.
 --
--- If no object is accessible by the path, return a prefix of the path that led to a non-formation when the remaining path wasn't empty.
+-- If no object is accessible by the path, return the path that led to a non-formation.
 -- >>> flip getObjectByPath ["org", "eolang"] "⟦ org ↦ ⟦ eolang ↦ ⟦ x ↦ ⟦ φ ↦ Φ.org.eolang.bool ( α0 ↦ Φ.org.eolang.bytes (Δ ⤍ 01-) ) ⟧, z ↦ ⟦ y ↦ ⟦ x ↦ ∅, φ ↦ ξ.x ⟧, φ ↦ Φ.org.eolang.bool ( α0 ↦ Φ.org.eolang.bytes (Δ ⤍ 01-) ) ⟧, λ ⤍ Package ⟧, λ ⤍ Package ⟧⟧"
--- Right (Formation [AlphaBinding (Label (LabelId "x")) (Formation [AlphaBinding Phi (Application (ObjectDispatch (ObjectDispatch (ObjectDispatch GlobalObject (Label (LabelId "org"))) (Label (LabelId "eolang"))) (Label (LabelId "bool"))) [AlphaBinding (Alpha (AlphaIndex "\945\&0")) (Application (ObjectDispatch (ObjectDispatch (ObjectDispatch GlobalObject (Label (LabelId "org"))) (Label (LabelId "eolang"))) (Label (LabelId "bytes"))) [DeltaBinding (Bytes "01-")])])]),AlphaBinding (Label (LabelId "z")) (Formation [AlphaBinding (Label (LabelId "y")) (Formation [EmptyBinding (Label (LabelId "x")),AlphaBinding Phi (ObjectDispatch ThisObject (Label (LabelId "x")))]),AlphaBinding Phi (Application (ObjectDispatch (ObjectDispatch (ObjectDispatch GlobalObject (Label (LabelId "org"))) (Label (LabelId "eolang"))) (Label (LabelId "bool"))) [AlphaBinding (Alpha (AlphaIndex "\945\&0")) (Application (ObjectDispatch (ObjectDispatch (ObjectDispatch GlobalObject (Label (LabelId "org"))) (Label (LabelId "eolang"))) (Label (LabelId "bytes"))) [DeltaBinding (Bytes "01-")])])]),LambdaBinding (Function "Package")])
+-- Right (Formation [AlphaBinding (AttributeNoSugar (Label (LabelId "x"))) (Formation [AlphaBinding (AttributeNoSugar Phi) (Application (ObjectDispatch (ObjectDispatch (ObjectDispatch GlobalObject (Label (LabelId "org"))) (Label (LabelId "eolang"))) (Label (LabelId "bool"))) [AlphaBinding (AttributeNoSugar (Alpha (AlphaIndex "\945\&0"))) (Application (ObjectDispatch (ObjectDispatch (ObjectDispatch GlobalObject (Label (LabelId "org"))) (Label (LabelId "eolang"))) (Label (LabelId "bytes"))) [DeltaBinding (Bytes "01-")])])]),AlphaBinding (AttributeNoSugar (Label (LabelId "z"))) (Formation [AlphaBinding (AttributeNoSugar (Label (LabelId "y"))) (Formation [EmptyBinding (Label (LabelId "x")),AlphaBinding (AttributeNoSugar Phi) (ObjectDispatch ThisObject (Label (LabelId "x")))]),AlphaBinding (AttributeNoSugar Phi) (Application (ObjectDispatch (ObjectDispatch (ObjectDispatch GlobalObject (Label (LabelId "org"))) (Label (LabelId "eolang"))) (Label (LabelId "bool"))) [AlphaBinding (AttributeNoSugar (Alpha (AlphaIndex "\945\&0"))) (Application (ObjectDispatch (ObjectDispatch (ObjectDispatch GlobalObject (Label (LabelId "org"))) (Label (LabelId "eolang"))) (Label (LabelId "bytes"))) [DeltaBinding (Bytes "01-")])])]),LambdaBinding (Function "Package")])
 --
 -- >>> flip getObjectByPath ["a"] "⟦ a ↦ ⟦ b ↦ ⟦ c ↦ ∅, d ↦ ⟦ φ ↦ ξ.ρ.c ⟧ ⟧, e ↦ ξ.b(c ↦ ⟦⟧).d ⟧.e ⟧"
--- Right (ObjectDispatch (Formation [AlphaBinding (Label (LabelId "b")) (Formation [EmptyBinding (Label (LabelId "c")),AlphaBinding (Label (LabelId "d")) (Formation [AlphaBinding Phi (ObjectDispatch (ObjectDispatch ThisObject Rho) (Label (LabelId "c")))])]),AlphaBinding (Label (LabelId "e")) (ObjectDispatch (Application (ObjectDispatch ThisObject (Label (LabelId "b"))) [AlphaBinding (Label (LabelId "c")) (Formation [])]) (Label (LabelId "d")))]) (Label (LabelId "e")))
+-- Left ["a"]
 getObjectByPath :: Object -> Path -> Either Path Object
 getObjectByPath object path =
   case path of
@@ -180,15 +182,15 @@ getObjectByPath object path =
               x <- bindings
               Right obj <-
                 case x of
-                  AlphaBinding (Alpha (AlphaIndex name)) obj | name == p -> [getObjectByPath obj ps]
-                  AlphaBinding (Label (LabelId name)) obj | name == p -> [getObjectByPath obj ps]
+                  AlphaBinding' (Alpha (AlphaIndex name)) obj@(Formation{}) | name == p -> [getObjectByPath obj ps]
+                  AlphaBinding' (Label (LabelId name)) obj@(Formation{}) | name == p -> [getObjectByPath obj ps]
                   _ -> [Left path]
               pure obj
         _ -> Left path
 
 -- | Get metrics for bindings of a formation that is accessible by a path within a given object.
 --
--- If no formation is accessible by the path, return a prefix of the path that led to a non-formation when the remaining path wasn't empty.
+-- If no formation is accessible by the path, return the path that led to a non-formation.
 -- >>> flip getBindingsByPathMetrics ["a"] "⟦ a ↦ ⟦ b ↦ ⟦ c ↦ ∅, d ↦ ⟦ φ ↦ ξ.ρ.c ⟧ ⟧, e ↦ ξ.b(c ↦ ⟦⟧).d ⟧.e ⟧"
 -- Left ["a"]
 --
@@ -203,8 +205,8 @@ getBindingsByPathMetrics object path =
           bindingsMetrics = do
             x <- zip bindings objectMetrics
             case x of
-              (AlphaBinding (Alpha (AlphaIndex name)) _, metrics) -> [BindingMetrics{..}]
-              (AlphaBinding (Label (LabelId name)) _, metrics) -> [BindingMetrics{..}]
+              (AlphaBinding' (Alpha (AlphaIndex name)) _, metrics) -> [BindingMetrics{..}]
+              (AlphaBinding' (Label (LabelId name)) _, metrics) -> [BindingMetrics{..}]
               _ -> []
        in Right $ BindingsByPathMetrics{..}
     Right _ -> Left path
@@ -214,7 +216,7 @@ getBindingsByPathMetrics object path =
 --
 -- Combine metrics produced by 'getThisObjectMetrics' and 'getBindingsByPathMetrics'.
 --
--- If no formation is accessible by the path, return a prefix of the path that led to a non-formation when the remaining path wasn't empty.
+-- If no formation is accessible by the path, return the path that led to a non-formation.
 -- >>> flip getObjectMetrics (Just ["a"]) "⟦ a ↦ ⟦ b ↦ ⟦ c ↦ ∅, d ↦ ⟦ φ ↦ ξ.ρ.c ⟧ ⟧, e ↦ ξ.b(c ↦ ⟦⟧).d ⟧.e ⟧"
 -- Left ["a"]
 --
@@ -223,14 +225,14 @@ getBindingsByPathMetrics object path =
 getObjectMetrics :: Object -> Maybe Path -> Either Path ObjectMetrics
 getObjectMetrics object path = do
   let thisObjectMetrics = getThisObjectMetrics object
-  bindingsByPathMetrics <- forM path $ \path' -> getBindingsByPathMetrics object path'
+  bindingsByPathMetrics <- forM path $ getBindingsByPathMetrics object
   pure ObjectMetrics{..}
 
--- | Get metrics for a program and for bindings of a formation accessible by a given path.
+-- | Get metrics for a program and for bindings of a formation accessible by the given path.
 --
 -- Combine metrics produced by 'getThisObjectMetrics' and 'getBindingsByPathMetrics'.
 --
--- If no formation is accessible by the path, return a prefix of the path that led to a non-formation when the remaining path wasn't empty.
+-- If no formation is accessible by the path, return the path that led to a non-formation.
 -- >>> flip getProgramMetrics (Just ["org", "eolang"]) "{⟦ org ↦ ⟦ eolang ↦ ⟦ x ↦ ⟦ φ ↦ Φ.org.eolang.bool ( α0 ↦ Φ.org.eolang.bytes (Δ ⤍ 01-) ) ⟧, z ↦ ⟦ y ↦ ⟦ x ↦ ∅, φ ↦ ξ.x ⟧, φ ↦ Φ.org.eolang.bool ( α0 ↦ Φ.org.eolang.bytes (Δ ⤍ 01-) ) ⟧, λ ⤍ Package ⟧, λ ⤍ Package ⟧⟧ }"
 -- Right (ProgramMetrics {bindingsByPathMetrics = Just (BindingsByPathMetrics {path = ["org","eolang"], bindingsMetrics = [BindingMetrics {name = "x", metrics = Metrics {dataless = 1, applications = 2, formations = 1, dispatches = 6}},BindingMetrics {name = "z", metrics = Metrics {dataless = 2, applications = 2, formations = 2, dispatches = 7}}]}), programMetrics = Metrics {dataless = 6, applications = 4, formations = 6, dispatches = 13}})
 --
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Preprocess.hs b/eo-phi-normalizer/src/Language/EO/Phi/Preprocess.hs
index 0252b0ad7..6eb072107 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Preprocess.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Preprocess.hs
@@ -22,15 +22,17 @@
 -- SOFTWARE.
 {- FOURMOLU_ENABLE -}
 {-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE LambdaCase #-}
 
 module Language.EO.Phi.Preprocess where
 
 import Control.Monad (void)
 import Data.Void (Void)
+import Language.EO.Phi.Syntax.Abs
 import Replace.Megaparsec (splitCap)
-import Text.Megaparsec (MonadParsec (..), Parsec, Stream (..), between, match, sepBy)
+import Text.Megaparsec (MonadParsec (..), Parsec, Stream (..), between, choice, match, oneOf, optional, sepBy)
 import Text.Megaparsec.Byte.Lexer qualified as L
-import Text.Megaparsec.Char (lowerChar, space)
+import Text.Megaparsec.Char (space, string)
 
 symbol :: String -> Parser String
 symbol = L.symbol space
@@ -40,41 +42,96 @@ lexeme = L.lexeme space
 
 type Parser = Parsec Void String
 
-parseLabelId :: Parser ()
+parseTail :: Parser String
+parseTail = takeWhileP (Just "LabelId") (`notElem` " \r\n\t,.|':;!?][}{)(⟧⟦↦")
+
+parseLabelId :: Parser LabelId
 parseLabelId = lexeme do
-  void lowerChar
-  void $ takeWhileP (Just "LabelId") (`notElem` " \r\n\t,.|':;!?][}{)(⟧⟦")
+  l <- oneOf ['a' .. 'z']
+  ls <- parseTail
+  pure $ LabelId (l : ls)
+
+parseToken :: String -> (String -> a) -> Parser a
+parseToken prefix cons = lexeme do
+  void $ string prefix
+  ls <- parseTail
+  pure $ cons (prefix <> ls)
+
+parseObjectMetaId :: Parser ObjectMetaId
+parseObjectMetaId = parseToken "!b" ObjectMetaId
+
+parseBytesMetaId :: Parser BytesMetaId
+parseBytesMetaId = parseToken "!y" BytesMetaId
+
+parseLabelMetaId :: Parser LabelMetaId
+parseLabelMetaId = parseToken "!τ" LabelMetaId
+
+parseMetaId :: Parser MetaId
+parseMetaId =
+  choice
+    [ MetaIdObject <$> parseObjectMetaId
+    , MetaIdBytes <$> parseBytesMetaId
+    , MetaIdLabel <$> parseLabelMetaId
+    ]
+
+parseAlphaIndex :: Parser AlphaIndex
+parseAlphaIndex = parseToken "α" AlphaIndex
+
+parseAttribute :: Parser Attribute
+parseAttribute = lexeme do
+  choice
+    [ Phi <$ symbol "φ"
+    , Rho <$ symbol "ρ"
+    , Label <$> parseLabelId
+    , Alpha <$> parseAlphaIndex
+    ]
 
 parseBindingArrow :: Parser ()
 parseBindingArrow = void $ symbol "↦"
 
-parseAlphaAttr :: Parser ()
-parseAlphaAttr = do
-  void parseLabelId
-  void $ between (symbol "(") (symbol ")") (sepBy parseLabelId (symbol ","))
-
-parseAlphaBindingSugar :: Parser ()
+parseAttributeSugar :: Parser AttributeSugar
+parseAttributeSugar = do
+  choice
+    [ do
+        labelId <- parseLabelId
+        attrs <- optional $ between (symbol "(") (symbol ")") (sepBy parseAttribute (symbol ","))
+        case attrs of
+          Nothing -> pure $ AttributeNoSugar (Label labelId)
+          Just attrs' -> pure $ AttributeSugar labelId attrs'
+    , AttributeNoSugar <$> parseAttribute
+    ]
+
+type Attr = Either MetaId AttributeSugar
+
+parseAlphaBindingSugar :: Parser Attr
 parseAlphaBindingSugar = do
-  parseAlphaAttr
+  attr <-
+    choice
+      [ Left <$> parseMetaId
+      , Right <$> parseAttributeSugar
+      ]
   parseBindingArrow
+  notFollowedBy (symbol "∅")
+  pure attr
 
-splitInput :: Parser a -> String -> [Either String (Tokens [Char])]
-splitInput sep = splitCap (fst <$> match sep)
+splitInput :: Parser a -> String -> [Either String (Tokens [Char], a)]
+splitInput sep = splitCap (match sep)
 
-addPrefix :: Parser a -> String -> [String]
-addPrefix sep = map (either id ("~" <>)) . splitInput sep
+addPrefix :: Parser Attr -> String -> [String]
+addPrefix sep = fmap (either id (\(x, a) -> choosePrefix a <> x)) . splitInput sep
+ where
+  choosePrefix = \case
+    Right AttributeSugar{} -> "~"
+    _ -> "#"
 
-preprocess' :: Parser a -> String -> String
+preprocess' :: Parser Attr -> String -> String
 preprocess' sep = concat . addPrefix sep
 
 preprocess :: String -> String
 preprocess = preprocess' parseAlphaBindingSugar
 
 input1 :: String
-input1 = "{⟦ org ↦ ⟦ eolang ↦ ⟦ number( as-bytes, abra  ) ↦ ⟦ φ ↦ ξ.as-bytes, neg ↦ ξ.times(-1), ⟧, λ ⤍ Package ⟧, λ ⤍ Package ⟧ ⟧}"
-
--- >>> addPrefix parseAlphaBindingSugar input1
--- ["{\10214 org \8614 \10214 eolang \8614 \10214 ","~number( as-bytes, abra  ) \8614 ","\10214 \966 \8614 \958.as-bytes, neg \8614 \958.times(-1), \10215, \955 \10509 Package \10215, \955 \10509 Package \10215 \10215}"]
+input1 = "{⟦ org ↦ ⟦ ⟧(α0 ↦ !b1) ⟧}"
 
 -- >>> preprocess input1
--- "{\10214 org \8614 \10214 eolang \8614 \10214 ~number( as-bytes, abra  ) \8614 \10214 \966 \8614 \958.as-bytes, neg \8614 \958.times(-1), \10215, \955 \10509 Package \10215, \955 \10509 Package \10215 \10215}"
+-- "{\10214 #org \8614 \10214 \10215(#\945\&0 \8614 !b1) \10215}"
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Pretty.hs b/eo-phi-normalizer/src/Language/EO/Phi/Pretty.hs
index 1faabd55f..1a3fc179c 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Pretty.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Pretty.hs
@@ -126,6 +126,11 @@ instance Pretty Abs.Binding where
     Abs.MetaBindings bindingsmetaid -> pretty bindingsmetaid
     Abs.MetaDeltaBinding bytesmetaid -> pretty "Δ ⤍" <+> pretty bytesmetaid
 
+instance Pretty Abs.AttributeSugar where
+  pretty = \case
+    Abs.AttributeSugar labelid labelids -> pretty labelid <> lparen <> pretty labelids <> rparen
+    Abs.AttributeNoSugar attribute -> pretty attribute
+
 instance {-# OVERLAPPING #-} Pretty [Abs.Binding] where
   pretty = vsep . punctuate comma . fmap pretty
 
@@ -136,8 +141,6 @@ instance Pretty Abs.Attribute where
     Abs.Label labelid -> pretty labelid
     Abs.Alpha alphaindex -> pretty alphaindex
     Abs.MetaAttr labelmetaid -> pretty labelmetaid
-    Abs.AttrSugar labelid labelids -> pretty labelid <> lparen <> pretty labelids <> rparen
-    Abs.PhiSugar labelids -> pretty Abs.Phi <> lparen <> pretty labelids <> rparen
 
 instance {-# OVERLAPPING #-} Pretty [Abs.LabelId] where
   pretty = hsep . punctuate comma . fmap pretty
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Rules/Common.hs b/eo-phi-normalizer/src/Language/EO/Phi/Rules/Common.hs
index 7c01340b0..5a939c27e 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Rules/Common.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Rules/Common.hs
@@ -27,6 +27,7 @@
 {-# LANGUAGE DerivingStrategies #-}
 {-# LANGUAGE GeneralisedNewtypeDeriving #-}
 {-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# OPTIONS_GHC -Wno-orphans #-}
 {-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
@@ -40,7 +41,22 @@ import Data.HashMap.Strict qualified as HashMap
 import Data.List (minimumBy, nubBy, sortOn)
 import Data.List.NonEmpty (NonEmpty (..), (<|))
 import Data.Ord (comparing)
-import Language.EO.Phi.Syntax
+import Language.EO.Phi.Syntax (
+  Attribute (..),
+  Binding (..),
+  BindingsMetaId (BindingsMetaId),
+  Bytes,
+  LabelId (LabelId),
+  LabelMetaId (LabelMetaId),
+  Object (..),
+  Program (..),
+  desugar,
+  errorExpectedDesugaredBinding,
+  errorExpectedDesugaredObject,
+  printTree,
+  pattern AlphaBinding',
+  pattern AlphaBinding'',
+ )
 
 -- $setup
 -- >>> :set -XOverloadedStrings
@@ -145,7 +161,7 @@ propagateName2 f (name, obj) bs = (name, f obj bs)
 
 withSubObjectBindings :: (Context -> Object -> [(String, Object)]) -> Context -> [Binding] -> [(String, [Binding])]
 withSubObjectBindings _ _ [] = []
-withSubObjectBindings f ctx (b@(AlphaBinding Rho _) : bs) =
+withSubObjectBindings f ctx (b@(AlphaBinding' Rho _) : bs) =
   -- do not apply rules inside ρ-bindings
   [(name, b : bs') | (name, bs') <- withSubObjectBindings f ctx bs]
 withSubObjectBindings f ctx (b : bs) =
@@ -156,7 +172,8 @@ withSubObjectBindings f ctx (b : bs) =
 
 withSubObjectBinding :: (Context -> Object -> [(String, Object)]) -> Context -> Binding -> [(String, Binding)]
 withSubObjectBinding f ctx = \case
-  AlphaBinding a obj -> propagateName1 (AlphaBinding a) <$> withSubObject f (ctx{currentAttr = a}) obj
+  AlphaBinding' a obj -> propagateName1 (AlphaBinding' a) <$> withSubObject f (ctx{currentAttr = a}) obj
+  b@AlphaBinding{} -> errorExpectedDesugaredBinding b
   b@AlphaBindingSugar{} -> errorExpectedDesugaredBinding b
   EmptyBinding{} -> []
   DeltaBinding{} -> []
@@ -258,7 +275,8 @@ equalObjectNamed x y = snd x `equalObject` snd y
 equalBindings :: [Binding] -> [Binding] -> Bool
 equalBindings bindings1 bindings2 = and (zipWith equalBinding (sortOn attr bindings1) (sortOn attr bindings2))
  where
-  attr (AlphaBinding a _) = a
+  attr (AlphaBinding' a _) = a
+  attr b@(AlphaBinding''{}) = errorExpectedDesugaredBinding b
   attr (EmptyBinding a) = a
   attr (DeltaBinding _) = Label (LabelId "Δ")
   attr DeltaEmptyBinding = Label (LabelId "Δ")
@@ -396,9 +414,10 @@ applyRulesChainWith limits@ApplicationLimits{..} obj
 -- | Lookup a binding by the attribute name.
 lookupBinding :: Attribute -> [Binding] -> Maybe Object
 lookupBinding _ [] = Nothing
-lookupBinding a (AlphaBinding a' object : bindings)
+lookupBinding a (AlphaBinding' a' object : bindings)
   | a == a' = Just object
   | otherwise = lookupBinding a bindings
+lookupBinding _ (b@(AlphaBinding''{}) : _) = errorExpectedDesugaredBinding b
 lookupBinding a (_ : bindings) = lookupBinding a bindings
 
 objectBindings :: Object -> [Binding]
@@ -408,7 +427,7 @@ objectBindings (ObjectDispatch obj _attr) = objectBindings obj
 objectBindings _ = []
 
 isRhoBinding :: Binding -> Bool
-isRhoBinding (AlphaBinding Rho _) = True
+isRhoBinding (AlphaBinding' Rho _) = True
 isRhoBinding _ = False
 
 hideRhoInBinding :: Binding -> Binding
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Rules/Fast.hs b/eo-phi-normalizer/src/Language/EO/Phi/Rules/Fast.hs
index 25eeda6ad..63aeae7e4 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Rules/Fast.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Rules/Fast.hs
@@ -36,8 +36,9 @@ import Language.EO.Phi.Syntax
 
 withBinding :: (Context -> Object -> Object) -> Context -> Binding -> Binding
 withBinding f ctx = \case
-  AlphaBinding Rho obj -> AlphaBinding Rho obj -- do not apply f inside ρ-bindings
-  AlphaBinding a obj -> AlphaBinding a (f ctx{currentAttr = a} obj)
+  AlphaBinding' Rho obj -> AlphaBinding' Rho obj -- do not apply f inside ρ-bindings
+  AlphaBinding' a obj -> AlphaBinding' a (f ctx{currentAttr = a} obj)
+  b@AlphaBinding''{} -> errorExpectedDesugaredBinding b
   binding -> binding
 
 isLambdaBinding :: Binding -> Bool
@@ -117,13 +118,13 @@ fastYegorInsideOut ctx = \case
       obj'@(Formation bindings) -> do
         let argBindings' = map (fastYegorInsideOutBinding ctx) argBindings
         case argBindings' of
-          [AlphaBinding (Alpha "α0") arg0, AlphaBinding (Alpha "α1") arg1, AlphaBinding (Alpha "α2") arg2] ->
+          [AlphaBinding' (Alpha "α0") arg0, AlphaBinding' (Alpha "α1") arg1, AlphaBinding' (Alpha "α2") arg2] ->
             case filter isEmptyBinding bindings of
               EmptyBinding a0 : EmptyBinding a1 : EmptyBinding a2 : _ ->
                 Formation
-                  ( AlphaBinding a0 arg0
-                      : AlphaBinding a1 arg1
-                      : AlphaBinding a2 arg2
+                  ( AlphaBinding' a0 arg0
+                      : AlphaBinding' a1 arg1
+                      : AlphaBinding' a2 arg2
                       : [ binding
                         | binding <- bindings
                         , case binding of
@@ -134,12 +135,12 @@ fastYegorInsideOut ctx = \case
               _
                 | not (any isLambdaBinding bindings) -> Termination
                 | otherwise -> Application obj' argBindings'
-          [AlphaBinding (Alpha "α0") arg0, AlphaBinding (Alpha "α1") arg1] ->
+          [AlphaBinding' (Alpha "α0") arg0, AlphaBinding' (Alpha "α1") arg1] ->
             case filter isEmptyBinding bindings of
               EmptyBinding a0 : EmptyBinding a1 : _ ->
                 Formation
-                  ( AlphaBinding a0 arg0
-                      : AlphaBinding a1 arg1
+                  ( AlphaBinding' a0 arg0
+                      : AlphaBinding' a1 arg1
                       : [ binding
                         | binding <- bindings
                         , case binding of
@@ -150,11 +151,11 @@ fastYegorInsideOut ctx = \case
               _
                 | not (any isLambdaBinding bindings) -> Termination
                 | otherwise -> Application obj' argBindings'
-          [AlphaBinding (Alpha "α0") arg0] ->
+          [AlphaBinding' (Alpha "α0") arg0] ->
             case filter isEmptyBinding bindings of
               EmptyBinding a0 : _ ->
                 Formation
-                  ( AlphaBinding a0 arg0
+                  ( AlphaBinding' a0 arg0
                       : [ binding
                         | binding <- bindings
                         , case binding of
@@ -165,10 +166,10 @@ fastYegorInsideOut ctx = \case
               _
                 | not (any isLambdaBinding bindings) -> Termination
                 | otherwise -> Application obj' argBindings'
-          [AlphaBinding a argA]
+          [AlphaBinding' a argA]
             | EmptyBinding a `elem` bindings ->
                 Formation
-                  ( AlphaBinding a argA
+                  ( AlphaBinding' a argA
                       : [ binding
                         | binding <- bindings
                         , case binding of
@@ -199,10 +200,11 @@ fastYegorInsideOut ctx = \case
           | binding <- bindings
           , let binding' =
                   case binding of
-                    AlphaBinding Rho _ -> binding
-                    AlphaBinding a objA -> do
+                    AlphaBinding' Rho _ -> binding
+                    AlphaBinding' a objA -> do
                       let ctx' = (extendContextWith root ctx){insideFormation = True, currentAttr = a}
-                      AlphaBinding a (fastYegorInsideOut ctx' objA)
+                      AlphaBinding' a (fastYegorInsideOut ctx' objA)
+                    b@AlphaBinding''{} -> errorExpectedDesugaredBinding b
                     _ -> binding
           ]
   obj@GlobalObjectPhiOrg -> errorExpectedDesugaredObject obj
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Rules/Yaml.hs b/eo-phi-normalizer/src/Language/EO/Phi/Rules/Yaml.hs
index 2e5a376ef..1071f47f5 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Rules/Yaml.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Rules/Yaml.hs
@@ -248,7 +248,8 @@ objectLabelIds = \case
 
 bindingLabelIds :: Binding -> Set LabelId
 bindingLabelIds = \case
-  AlphaBinding a obj -> objectLabelIds obj <> attrLabelIds a
+  AlphaBinding' a obj -> objectLabelIds obj <> attrLabelIds a
+  b@AlphaBinding{} -> errorExpectedDesugaredBinding b
   DeltaBinding _bytes -> mempty
   EmptyBinding a -> attrLabelIds a
   DeltaEmptyBinding -> mempty
@@ -299,7 +300,8 @@ objectMetaIds obj@ConstFloat{} = objectMetaIds (desugar obj)
 objectMetaIds obj@ConstFloatRaw{} = errorExpectedDesugaredObject obj
 
 bindingMetaIds :: Binding -> Set MetaId
-bindingMetaIds (AlphaBinding attr obj) = attrMetaIds attr <> objectMetaIds obj
+bindingMetaIds (AlphaBinding' attr obj) = attrMetaIds attr <> objectMetaIds obj
+bindingMetaIds b@AlphaBinding{} = errorExpectedDesugaredBinding b
 bindingMetaIds (EmptyBinding attr) = attrMetaIds attr
 bindingMetaIds (DeltaBinding _) = mempty
 bindingMetaIds DeltaEmptyBinding = mempty
@@ -314,8 +316,6 @@ attrMetaIds Rho = mempty
 attrMetaIds (Label _) = mempty
 attrMetaIds (Alpha _) = mempty
 attrMetaIds (MetaAttr x) = Set.singleton (MetaIdLabel x)
-attrMetaIds a@(AttrSugar{}) = errorExpectedDesugaredAttribute a
-attrMetaIds a@(PhiSugar{}) = errorExpectedDesugaredAttribute a
 
 objectHasMetavars :: Object -> Bool
 objectHasMetavars (Formation bindings) = any bindingHasMetavars bindings
@@ -338,7 +338,8 @@ objectHasMetavars obj@ConstFloat{} = objectHasMetavars (desugar obj)
 objectHasMetavars obj@ConstFloatRaw{} = errorExpectedDesugaredObject obj
 
 bindingHasMetavars :: Binding -> Bool
-bindingHasMetavars (AlphaBinding attr obj) = attrHasMetavars attr || objectHasMetavars obj
+bindingHasMetavars (AlphaBinding' attr obj) = attrHasMetavars attr || objectHasMetavars obj
+bindingHasMetavars b@(AlphaBinding''{}) = errorExpectedDesugaredBinding b
 bindingHasMetavars (EmptyBinding attr) = attrHasMetavars attr
 bindingHasMetavars (DeltaBinding _) = False
 bindingHasMetavars DeltaEmptyBinding = False
@@ -353,8 +354,6 @@ attrHasMetavars Rho = False
 attrHasMetavars (Label _) = False
 attrHasMetavars (Alpha _) = False
 attrHasMetavars (MetaAttr _) = True
-attrHasMetavars a@AttrSugar{} = errorExpectedDesugaredAttribute a
-attrHasMetavars a@PhiSugar{} = errorExpectedDesugaredAttribute a
 
 -- | Given a condition, and a substition from object matching
 --   tells whether the condition matches the object
@@ -387,7 +386,7 @@ checkCond ctx (ApplyInAbstractSubformations shouldApply) _subst
 hasAttr :: RuleAttribute -> [Binding] -> Bool
 hasAttr attr = any (isAttr attr)
  where
-  isAttr (ObjectAttr a) (AlphaBinding a' _) = a == a'
+  isAttr (ObjectAttr a) (AlphaBinding' a' _) = a == a'
   isAttr (ObjectAttr a) (EmptyBinding a') = a == a'
   isAttr DeltaAttr (DeltaBinding _) = True
   isAttr DeltaAttr DeltaEmptyBinding = True
@@ -485,8 +484,9 @@ applySubstBindings subst = concatMap (applySubstBinding subst)
 
 applySubstBinding :: Subst -> Binding -> [Binding]
 applySubstBinding subst@Subst{..} = \case
-  AlphaBinding a obj ->
-    [AlphaBinding (applySubstAttr subst a) (applySubst subst obj)]
+  AlphaBinding' a obj ->
+    [AlphaBinding' (applySubstAttr subst a) (applySubst subst obj)]
+  b@AlphaBinding{} -> errorExpectedDesugaredBinding b
   EmptyBinding a ->
     [EmptyBinding (applySubstAttr subst a)]
   DeltaBinding bytes -> [DeltaBinding (coerce bytes)]
@@ -616,7 +616,7 @@ matchFindBinding p bindings =
 
 matchBinding :: Binding -> Binding -> [Subst]
 matchBinding MetaBindings{} _ = []
-matchBinding (AlphaBinding a obj) (AlphaBinding a' obj') = do
+matchBinding (AlphaBinding' a obj) (AlphaBinding' a' obj') = do
   subst1 <- matchAttr a a'
   subst2 <- matchObject obj obj'
   pure (subst1 <> subst2)
@@ -641,7 +641,7 @@ matchAttr _ _ = []
 substThis :: Object -> Object -> Object
 substThis thisObj = go
  where
-  isAttachedRho (AlphaBinding Rho _) = True
+  isAttachedRho (AlphaBinding' Rho _) = True
   isAttachedRho _ = False
 
   isEmptyRho (EmptyBinding Rho) = True
@@ -652,7 +652,7 @@ substThis thisObj = go
     -- IMPORTANT: we are injecting a ρ-attribute in formations!
     obj@(Formation bindings)
       | any isAttachedRho bindings -> obj
-      | otherwise -> Formation (filter (not . isEmptyRho) bindings ++ [AlphaBinding Rho thisObj])
+      | otherwise -> Formation (filter (not . isEmptyRho) bindings ++ [AlphaBinding' Rho thisObj])
     -- everywhere else we simply recursively traverse the φ-term
     Application obj bindings -> Application (go obj) (map (substThisBinding thisObj) bindings)
     ObjectDispatch obj a -> ObjectDispatch (go obj) a
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Syntax.hs b/eo-phi-normalizer/src/Language/EO/Phi/Syntax.hs
index c8ff8840b..de78d9627 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Syntax.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Syntax.hs
@@ -82,13 +82,19 @@ module Language.EO.Phi.Syntax (
   errorExpectedDesugaredObject,
   errorExpectedDesugaredBinding,
   errorExpectedDesugaredAttribute,
+
+  -- * Pattern synonyms
+  pattern AlphaBinding',
+  pattern AlphaBinding'',
 ) where
 
 import Data.ByteString (ByteString)
 import Data.ByteString qualified as ByteString.Strict
 import Data.Char (toUpper)
+import Data.Foldable1 (intercalate1)
 import Data.Int
 import Data.List (intercalate)
+import Data.List.NonEmpty (NonEmpty ((:|)))
 import Data.Serialize qualified as Serialize
 import Data.String (IsString (fromString))
 import Data.Text qualified as T
@@ -105,6 +111,7 @@ import Prettyprinter (LayoutOptions (..), PageWidth (..), Pretty (pretty), defau
 import Prettyprinter.Render.Text (renderStrict)
 import PyF (fmt)
 import Text.Printf (printf)
+import Validation (Validation (..))
 
 -- $setup
 -- >>> :set -XOverloadedStrings
@@ -154,14 +161,11 @@ instance DesugarableInitially [Binding] where
    where
     go :: Int -> Binding -> Binding
     go idx = \case
-      AlphaBinding (AttrSugar l ls) (Formation bindings) ->
-        let bindingsDesugared = desugarInitially bindings
-         in AlphaBinding (Label l) (Formation ((EmptyBinding . Label <$> ls) <> bindingsDesugared))
-      AlphaBinding (PhiSugar ls) (Formation bindings) ->
+      AlphaBinding'' l ls (Formation bindings) ->
         let bindingsDesugared = desugarInitially bindings
-         in AlphaBinding Phi (Formation ((EmptyBinding . Label <$> ls) <> bindingsDesugared))
+         in AlphaBinding' (Label l) (Formation ((EmptyBinding <$> ls) <> bindingsDesugared))
       AlphaBinding a obj -> AlphaBinding a (desugarInitially obj)
-      AlphaBindingSugar obj -> AlphaBinding (Alpha (AlphaIndex [fmt|α{idx}|])) (desugarInitially obj)
+      AlphaBindingSugar obj -> AlphaBinding' (Alpha (AlphaIndex [fmt|α{idx}|])) (desugarInitially obj)
       binding -> binding
 
 instance DesugarableInitially Program where
@@ -174,12 +178,71 @@ instance DesugarableInitially Binding where
     AlphaBinding a obj -> AlphaBinding a (desugarInitially obj)
     obj -> obj
 
+instance DesugarableInitially AttributeSugar
 instance DesugarableInitially Attribute
 instance DesugarableInitially RuleAttribute
 instance DesugarableInitially PeeledObject
 instance DesugarableInitially ObjectHead
 instance DesugarableInitially MetaId
 
+class CheckableSyntaxInitially a where
+  checkSyntax :: a -> Validation (NonEmpty String) a
+  checkSyntax = pure
+
+instance CheckableSyntaxInitially Program where
+  checkSyntax (Program bindings) = Program <$> traverse checkSyntax bindings
+
+instance CheckableSyntaxInitially Binding where
+  checkSyntax = \case
+    AlphaBinding' a obj -> AlphaBinding' a <$> checkSyntax obj
+    AlphaBinding'' a as obj ->
+      case (as, obj) of
+        -- inline-voids-on-application
+        -- {⟦ k() ↦ ⟦ ⟧() ⟧}
+        ([], o@(Application (Formation []) [])) -> Failure (printTree o :| [])
+        -- inline-voids-on-dispatch
+        -- {⟦ k() ↦ ⟦ ⟧.x ⟧}
+        ([], o@(ObjectDispatch (Formation []) _)) -> Failure (printTree o :| [])
+        _ -> AlphaBinding'' a as <$> checkSyntax obj
+    AlphaBindingSugar obj -> AlphaBindingSugar <$> checkSyntax obj
+    b -> pure b
+
+instance CheckableSyntaxInitially Object where
+  checkSyntax = \case
+    -- application-to-formation
+    -- {⟦ k ↦ ⟦ ⟧ (t ↦ ξ.t) ⟧}
+    o@(Application (Formation []) [_]) -> Failure (printTree o :| [])
+    o@(Application _ xs)
+      | let
+          isBadBinding = \case
+            -- delta-in-application
+            -- {⟦ k ↦ ξ.t (Δ ⤍ 42-) ⟧}
+            DeltaBinding{} -> True
+            DeltaEmptyBinding{} -> True
+            -- lambda-in-application
+            -- {⟦ k ↦ ξ.t (λ ⤍ Fn) ⟧}
+            LambdaBinding{} -> True
+            -- void-as-value
+            -- {⟦ k ↦ ξ.t (t ↦ ∅) ⟧}
+            EmptyBinding{} -> True
+            _ -> False
+         in
+          [d | d <- xs, isBadBinding d] /= [] ->
+          Failure (printTree o :| [])
+    ObjectDispatch obj x -> ObjectDispatch <$> checkSyntax obj <*> pure x
+    MetaSubstThis obj1 obj2 -> MetaSubstThis <$> checkSyntax obj1 <*> checkSyntax obj2
+    MetaContextualize obj1 obj2 -> MetaContextualize <$> checkSyntax obj1 <*> checkSyntax obj2
+    MetaTailContext obj x -> MetaTailContext <$> checkSyntax obj <*> pure x
+    MetaFunction n obj -> MetaFunction n <$> checkSyntax obj
+    x -> pure x
+
+instance CheckableSyntaxInitially Attribute
+instance CheckableSyntaxInitially AttributeSugar
+instance CheckableSyntaxInitially RuleAttribute
+instance CheckableSyntaxInitially PeeledObject
+instance CheckableSyntaxInitially ObjectHead
+instance CheckableSyntaxInitially MetaId
+
 class SugarableFinally a where
   sugarFinally :: a -> a
   sugarFinally = id
@@ -189,7 +252,7 @@ instance SugarableFinally Program where
   sugarFinally (Program bindings) = Program (sugarFinally bindings)
 
 pattern SugarBinding :: Bytes -> Binding
-pattern SugarBinding bs <- AlphaBinding "as-bytes" (Application "Φ.org.eolang.bytes" [AlphaBinding "α0" (Formation [DeltaBinding bs])])
+pattern SugarBinding bs <- AlphaBinding' "as-bytes" (Application "Φ.org.eolang.bytes" [AlphaBinding' "α0" (Formation [DeltaBinding bs])])
 
 instance SugarableFinally Object where
   sugarFinally :: Object -> Object
@@ -231,9 +294,8 @@ instance SugarableFinally [Binding] where
     go :: Int -> Binding -> Bool
     go idx = \case
       obj@AlphaBindingSugar{} -> errorExpectedDesugaredBinding obj
-      obj@(AlphaBinding (AttrSugar _ _) _) -> errorExpectedDesugaredBinding obj
-      obj@(AlphaBinding (PhiSugar _) _) -> errorExpectedDesugaredBinding obj
-      AlphaBinding (Alpha (AlphaIndex ('α' : idx'))) _ -> idx == read idx'
+      obj@(AlphaBinding''{}) -> errorExpectedDesugaredBinding obj
+      AlphaBinding' (Alpha (AlphaIndex ('α' : idx'))) _ -> idx == read idx'
       _ -> False
 
 instance SugarableFinally Binding where
@@ -275,12 +337,12 @@ desugar = \case
 
 desugarBinding :: Binding -> Binding
 desugarBinding = \case
-  AlphaBinding (AttrSugar l ls) (Formation bindings) ->
+  AlphaBinding'' l ls (Formation bindings) ->
     let bindingsDesugared = desugarBinding <$> bindings
-     in AlphaBinding (Label l) (Formation ((EmptyBinding . Label <$> ls) <> bindingsDesugared))
-  AlphaBinding (PhiSugar ls) (Formation bindings) ->
+     in AlphaBinding' (Label l) (Formation ((EmptyBinding <$> ls) <> bindingsDesugared))
+  AlphaBinding' l (Formation bindings) ->
     let bindingsDesugared = desugarBinding <$> bindings
-     in AlphaBinding Phi (Formation ((EmptyBinding . Label <$> ls) <> bindingsDesugared))
+     in AlphaBinding' l (Formation bindingsDesugared)
   AlphaBinding a obj -> AlphaBinding a (desugar obj)
   obj@(AlphaBindingSugar{}) -> errorExpectedDesugaredBinding obj
   binding -> binding
@@ -663,21 +725,32 @@ instance IsString Program where fromString = unsafeParseWith pProgram
 instance IsString Object where fromString = unsafeParseWith pObject
 instance IsString Binding where fromString = unsafeParseWith pBinding
 instance IsString Attribute where fromString = unsafeParseWith pAttribute
+instance IsString AttributeSugar where fromString = unsafeParseWith pAttributeSugar
 instance IsString RuleAttribute where fromString = unsafeParseWith pRuleAttribute
 instance IsString PeeledObject where fromString = unsafeParseWith pPeeledObject
 instance IsString ObjectHead where fromString = unsafeParseWith pObjectHead
 instance IsString MetaId where fromString = unsafeParseWith pMetaId
 
-parseWith :: (DesugarableInitially a) => ([Token] -> Either String a) -> String -> Either String a
-parseWith parser input = either (\x -> Left [fmt|{x}\non the input:\n{input'}|]) (Right . desugarInitially) parsed
+parseWith :: (DesugarableInitially a, CheckableSyntaxInitially a) => ([Token] -> Either String a) -> String -> Either String a
+parseWith parser input = result
  where
   input' = preprocess input
   tokens = myLexer input'
   parsed = parser tokens
-
--- | Parse a 'Object' from a 'String'.
+  validated = checkSyntax <$> parsed
+  mkError :: String -> Either String a
+  mkError x = Left [fmt|{x}\non the input:\n{input'}|]
+  result =
+    case validated of
+      Left x -> mkError x
+      Right x ->
+        case x of
+          Failure y -> mkError [fmt|Bad sub-expressions:\n\n{intercalate1 "\n\n" y}\n|]
+          Success y -> Right (desugarInitially y)
+
+-- | Parse an 'Object' from a 'String'.
 -- May throw an 'error` if input has a syntactical or lexical errors.
-unsafeParseWith :: (DesugarableInitially a) => ([Token] -> Either String a) -> String -> a
+unsafeParseWith :: (DesugarableInitially a, CheckableSyntaxInitially a) => ([Token] -> Either String a) -> String -> a
 unsafeParseWith parser input =
   case parseWith parser input of
     Left parseError -> error parseError
@@ -698,3 +771,11 @@ printTree =
 
 -- >>> bytesToInt "00-00-00-00-00-00-00-00"
 -- 0
+
+pattern AlphaBinding' :: Attribute -> Object -> Binding
+pattern AlphaBinding' a obj = AlphaBinding (AttributeNoSugar a) obj
+
+pattern AlphaBinding'' :: LabelId -> [Attribute] -> Object -> Binding
+pattern AlphaBinding'' a as obj = AlphaBinding (AttributeSugar a as) obj
+
+{-# COMPLETE AlphaBinding', AlphaBinding'', EmptyBinding, DeltaBinding, DeltaEmptyBinding, LambdaBinding, MetaBindings, MetaDeltaBinding, AlphaBindingSugar #-}
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Abs.hs b/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Abs.hs
index fb120850e..41353cd9a 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Abs.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Abs.hs
@@ -81,7 +81,7 @@ data Object
   deriving (C.Eq, C.Ord, C.Show, C.Read, C.Data, C.Typeable, C.Generic)
 
 data Binding
-    = AlphaBinding Attribute Object
+    = AlphaBinding AttributeSugar Object
     | AlphaBindingSugar Object
     | EmptyBinding Attribute
     | DeltaBinding Bytes
@@ -91,14 +91,16 @@ data Binding
     | MetaDeltaBinding BytesMetaId
   deriving (C.Eq, C.Ord, C.Show, C.Read, C.Data, C.Typeable, C.Generic)
 
+data AttributeSugar
+    = AttributeNoSugar Attribute | AttributeSugar LabelId [Attribute]
+  deriving (C.Eq, C.Ord, C.Show, C.Read, C.Data, C.Typeable, C.Generic)
+
 data Attribute
     = Phi
-    | PhiSugar [LabelId]
     | Rho
     | Label LabelId
     | Alpha AlphaIndex
     | MetaAttr LabelMetaId
-    | AttrSugar LabelId [LabelId]
   deriving (C.Eq, C.Ord, C.Show, C.Read, C.Data, C.Typeable, C.Generic)
 
 data RuleAttribute = ObjectAttr Attribute | DeltaAttr | LambdaAttr
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Doc.txt b/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Doc.txt
index 321b1d3ee..1ada8b0fc 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Doc.txt
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Doc.txt
@@ -44,38 +44,38 @@ Bytes literals are recognized by the regular expression
 
 Function literals are recognized by the regular expression
 `````upper (char - ["
-
 !'(),-.:;?[]{|}⟦⟧"])*`````
+
 !'(),-.:;?[]{|}↦⟦⟧"])*`````
 
 LabelId literals are recognized by the regular expression
 `````lower (char - ["
-
 !'(),.:;?[]{|}⟦⟧"])*`````
+
 !'(),.:;?[]{|}↦⟦⟧"])*`````
 
 AlphaIndex literals are recognized by the regular expression
 `````{"α0"} | 'α' (digit - '0') digit*`````
 
 LabelMetaId literals are recognized by the regular expression
 `````{"!τ"} (char - ["
-
 !'(),-.:;?[]{|}⟦⟧"])*`````
+
 !'(),-.:;?[]{|}↦⟦⟧"])*`````
 
 TailMetaId literals are recognized by the regular expression
 `````{"!t"} (char - ["
-
 !'(),-.:;?[]{|}⟦⟧"])*`````
+
 !'(),-.:;?[]{|}↦⟦⟧"])*`````
 
 BindingsMetaId literals are recognized by the regular expression
 `````{"!B"} (char - ["
-
 !'(),-.:;?[]{|}⟦⟧"])*`````
+
 !'(),-.:;?[]{|}↦⟦⟧"])*`````
 
 ObjectMetaId literals are recognized by the regular expression
 `````{"!b"} (char - ["
-
 !'(),-.:;?[]{|}⟦⟧"])*`````
+
 !'(),-.:;?[]{|}↦⟦⟧"])*`````
 
 BytesMetaId literals are recognized by the regular expression
 `````{"!y"} (char - ["
-
 !'(),-.:;?[]{|}⟦⟧"])*`````
+
 !'(),-.:;?[]{|}↦⟦⟧"])*`````
 
 MetaFunctionName literals are recognized by the regular expression
 `````'@' (char - ["
-
 !'(),-.:;?[]{|}⟦⟧"])*`````
+
 !'(),-.:;?[]{|}↦⟦⟧"])*`````
 
 IntegerSigned literals are recognized by the regular expression
 `````'-'? digit+`````
@@ -99,7 +99,7 @@ The symbols used in Syntax are the following:
   | ( | ) | . | Φ̇
   | ⊥ | [ | ↦ | ]
   | ⌈ | , | ⌉ | *
-  | ∅ | ⤍ | ~ |
+  | ∅ | ⤍ | # | ~
 
 ===Comments===
 Single-line comments begin with //.Multiple-line comments are  enclosed with /* and */.
@@ -131,7 +131,7 @@ All other symbols are terminals.
   |  |  **|**  | //ObjectMetaId//
   |  |  **|**  | //Object// ``*`` //TailMetaId//
   |  |  **|**  | //MetaFunctionName// ``(`` //Object// ``)``
-  | //Binding// | -> | //Attribute// ``↦`` //Object//
+  | //Binding// | -> | //AttributeSugar// ``↦`` //Object//
   |  |  **|**  | //Object//
   |  |  **|**  | //Attribute// ``↦`` ``∅``
   |  |  **|**  | ``Δ`` ``⤍`` //Bytes//
@@ -142,16 +142,16 @@ All other symbols are terminals.
   | //[Binding]// | -> | **eps**
   |  |  **|**  | //Binding//
   |  |  **|**  | //Binding// ``,`` //[Binding]//
+  | //AttributeSugar// | -> | ``#`` //Attribute//
+  |  |  **|**  | ``~`` //LabelId// ``(`` //[Attribute]// ``)``
+  | //[Attribute]// | -> | **eps**
+  |  |  **|**  | //Attribute//
+  |  |  **|**  | //Attribute// ``,`` //[Attribute]//
   | //Attribute// | -> | ``φ``
-  |  |  **|**  | ``~`` ``φ`` ``(`` //[LabelId]// ``)``
   |  |  **|**  | ``ρ``
   |  |  **|**  | //LabelId//
   |  |  **|**  | //AlphaIndex//
   |  |  **|**  | //LabelMetaId//
-  |  |  **|**  | ``~`` //LabelId// ``(`` //[LabelId]// ``)``
-  | //[LabelId]// | -> | **eps**
-  |  |  **|**  | //LabelId//
-  |  |  **|**  | //LabelId// ``,`` //[LabelId]//
   | //RuleAttribute// | -> | //Attribute//
   |  |  **|**  | ``Δ``
   |  |  **|**  | ``λ``
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Lex.x b/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Lex.x
index 945d1192c..368574891 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Lex.x
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Lex.x
@@ -28,7 +28,7 @@ $u = [. \n]          -- universal: any character
 
 -- Symbols and non-identifier-like reserved words
 
-@rsyms = \Φ | \ξ | \Δ | \λ | \φ | \ρ | \{ | \⟦ | \⟧ | \} | \( | \) | \. | \Φ \̇ | \⊥ | \[ | \↦ | \] | \⌈ | \, | \⌉ | \* | \∅ | \⤍ | \~
+@rsyms = \Φ | \ξ | \Δ | \λ | \φ | \ρ | \{ | \⟦ | \⟧ | \} | \( | \) | \. | \Φ \̇ | \⊥ | \[ | \↦ | \] | \⌈ | \, | \⌉ | \* | \∅ | \⤍ | \# | \~
 
 :-
 
@@ -50,11 +50,11 @@ $white+ ;
     { tok (eitherResIdent T_Bytes) }
 
 -- token Function
-$c [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \⟦ \⟧]] *
+$c [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \↦ \⟦ \⟧]] *
     { tok (eitherResIdent T_Function) }
 
 -- token LabelId
-$s [$u # [\t \n \r \  \! \' \( \) \, \. \: \; \? \[ \] \{ \| \} \⟦ \⟧]] *
+$s [$u # [\t \n \r \  \! \' \( \) \, \. \: \; \? \[ \] \{ \| \} \↦ \⟦ \⟧]] *
     { tok (eitherResIdent T_LabelId) }
 
 -- token AlphaIndex
@@ -62,27 +62,27 @@ $s [$u # [\t \n \r \  \! \' \( \) \, \. \: \; \? \[ \] \{ \| \} \⟦ \⟧]] *
     { tok (eitherResIdent T_AlphaIndex) }
 
 -- token LabelMetaId
-\! τ [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \⟦ \⟧]] *
+\! τ [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \↦ \⟦ \⟧]] *
     { tok (eitherResIdent T_LabelMetaId) }
 
 -- token TailMetaId
-\! t [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \⟦ \⟧]] *
+\! t [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \↦ \⟦ \⟧]] *
     { tok (eitherResIdent T_TailMetaId) }
 
 -- token BindingsMetaId
-\! B [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \⟦ \⟧]] *
+\! B [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \↦ \⟦ \⟧]] *
     { tok (eitherResIdent T_BindingsMetaId) }
 
 -- token ObjectMetaId
-\! b [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \⟦ \⟧]] *
+\! b [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \↦ \⟦ \⟧]] *
     { tok (eitherResIdent T_ObjectMetaId) }
 
 -- token BytesMetaId
-\! y [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \⟦ \⟧]] *
+\! y [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \↦ \⟦ \⟧]] *
     { tok (eitherResIdent T_BytesMetaId) }
 
 -- token MetaFunctionName
-\@ [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \⟦ \⟧]] *
+\@ [$u # [\t \n \r \  \! \' \( \) \, \- \. \: \; \? \[ \] \{ \| \} \↦ \⟦ \⟧]] *
     { tok (eitherResIdent T_MetaFunctionName) }
 
 -- token IntegerSigned
@@ -240,19 +240,20 @@ eitherResIdent tv s = treeFind resWords
 -- | The keywords and symbols of the language organized as binary search tree.
 resWords :: BTree
 resWords =
-  b "\934\775" 13
-    (b "]" 7
-       (b "," 4
-          (b ")" 2 (b "(" 1 N N) (b "*" 3 N N)) (b "[" 6 (b "." 5 N N) N))
-       (b "~" 10
-          (b "}" 9 (b "{" 8 N N) N) (b "\934" 12 (b "\916" 11 N N) N)))
-    (b "\8869" 20
-       (b "\966" 17
-          (b "\958" 15 (b "\955" 14 N N) (b "\961" 16 N N))
-          (b "\8709" 19 (b "\8614" 18 N N) N))
-       (b "\10214" 23
-          (b "\8969" 22 (b "\8968" 21 N N) N)
-          (b "\10509" 25 (b "\10215" 24 N N) N)))
+  b "\934\775" 14
+    (b "[" 7
+       (b "*" 4
+          (b "(" 2 (b "#" 1 N N) (b ")" 3 N N)) (b "." 6 (b "," 5 N N) N))
+       (b "~" 11
+          (b "{" 9 (b "]" 8 N N) (b "}" 10 N N))
+          (b "\934" 13 (b "\916" 12 N N) N)))
+    (b "\8869" 21
+       (b "\966" 18
+          (b "\958" 16 (b "\955" 15 N N) (b "\961" 17 N N))
+          (b "\8709" 20 (b "\8614" 19 N N) N))
+       (b "\10214" 24
+          (b "\8969" 23 (b "\8968" 22 N N) N)
+          (b "\10509" 26 (b "\10215" 25 N N) N)))
   where
   b s n = B bs (TS bs n)
     where
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Par.y b/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Par.y
index 349549b5f..b535cc9d4 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Par.y
+++ b/eo-phi-normalizer/src/Language/EO/Phi/Syntax/Par.y
@@ -13,8 +13,9 @@ module Language.EO.Phi.Syntax.Par
   , pObject
   , pBinding
   , pListBinding
+  , pAttributeSugar
+  , pListAttribute
   , pAttribute
-  , pListLabelId
   , pRuleAttribute
   , pPeeledObject
   , pObjectHead
@@ -34,8 +35,9 @@ import Language.EO.Phi.Syntax.Lex
 %name pObject Object
 %name pBinding Binding
 %name pListBinding ListBinding
+%name pAttributeSugar AttributeSugar
+%name pListAttribute ListAttribute
 %name pAttribute Attribute
-%name pListLabelId ListLabelId
 %name pRuleAttribute RuleAttribute
 %name pPeeledObject PeeledObject
 %name pObjectHead ObjectHead
@@ -45,31 +47,32 @@ import Language.EO.Phi.Syntax.Lex
 %monad { Err } { (>>=) } { return }
 %tokentype {Token}
 %token
-  '('                { PT _ (TS _ 1)                }
-  ')'                { PT _ (TS _ 2)                }
-  '*'                { PT _ (TS _ 3)                }
-  ','                { PT _ (TS _ 4)                }
-  '.'                { PT _ (TS _ 5)                }
-  '['                { PT _ (TS _ 6)                }
-  ']'                { PT _ (TS _ 7)                }
-  '{'                { PT _ (TS _ 8)                }
-  '}'                { PT _ (TS _ 9)                }
-  '~'                { PT _ (TS _ 10)               }
-  'Δ'                { PT _ (TS _ 11)               }
-  'Φ'                { PT _ (TS _ 12)               }
-  'Φ̇'               { PT _ (TS _ 13)               }
-  'λ'                { PT _ (TS _ 14)               }
-  'ξ'                { PT _ (TS _ 15)               }
-  'ρ'                { PT _ (TS _ 16)               }
-  'φ'                { PT _ (TS _ 17)               }
-  '↦'                { PT _ (TS _ 18)               }
-  '∅'                { PT _ (TS _ 19)               }
-  '⊥'                { PT _ (TS _ 20)               }
-  '⌈'                { PT _ (TS _ 21)               }
-  '⌉'                { PT _ (TS _ 22)               }
-  '⟦'                { PT _ (TS _ 23)               }
-  '⟧'                { PT _ (TS _ 24)               }
-  '⤍'                { PT _ (TS _ 25)               }
+  '#'                { PT _ (TS _ 1)                }
+  '('                { PT _ (TS _ 2)                }
+  ')'                { PT _ (TS _ 3)                }
+  '*'                { PT _ (TS _ 4)                }
+  ','                { PT _ (TS _ 5)                }
+  '.'                { PT _ (TS _ 6)                }
+  '['                { PT _ (TS _ 7)                }
+  ']'                { PT _ (TS _ 8)                }
+  '{'                { PT _ (TS _ 9)                }
+  '}'                { PT _ (TS _ 10)               }
+  '~'                { PT _ (TS _ 11)               }
+  'Δ'                { PT _ (TS _ 12)               }
+  'Φ'                { PT _ (TS _ 13)               }
+  'Φ̇'               { PT _ (TS _ 14)               }
+  'λ'                { PT _ (TS _ 15)               }
+  'ξ'                { PT _ (TS _ 16)               }
+  'ρ'                { PT _ (TS _ 17)               }
+  'φ'                { PT _ (TS _ 18)               }
+  '↦'                { PT _ (TS _ 19)               }
+  '∅'                { PT _ (TS _ 20)               }
+  '⊥'                { PT _ (TS _ 21)               }
+  '⌈'                { PT _ (TS _ 22)               }
+  '⌉'                { PT _ (TS _ 23)               }
+  '⟦'                { PT _ (TS _ 24)               }
+  '⟧'                { PT _ (TS _ 25)               }
+  '⤍'                { PT _ (TS _ 26)               }
   L_doubl            { PT _ (TD $$)                 }
   L_integ            { PT _ (TI $$)                 }
   L_quoted           { PT _ (TL $$)                 }
@@ -169,7 +172,7 @@ Object
 
 Binding :: { Language.EO.Phi.Syntax.Abs.Binding }
 Binding
-  : Attribute '↦' Object { Language.EO.Phi.Syntax.Abs.AlphaBinding $1 $3 }
+  : AttributeSugar '↦' Object { Language.EO.Phi.Syntax.Abs.AlphaBinding $1 $3 }
   | Object { Language.EO.Phi.Syntax.Abs.AlphaBindingSugar $1 }
   | Attribute '↦' '∅' { Language.EO.Phi.Syntax.Abs.EmptyBinding $1 }
   | 'Δ' '⤍' Bytes { Language.EO.Phi.Syntax.Abs.DeltaBinding $3 }
@@ -184,21 +187,24 @@ ListBinding
   | Binding { (:[]) $1 }
   | Binding ',' ListBinding { (:) $1 $3 }
 
+AttributeSugar :: { Language.EO.Phi.Syntax.Abs.AttributeSugar }
+AttributeSugar
+  : '#' Attribute { Language.EO.Phi.Syntax.Abs.AttributeNoSugar $2 }
+  | '~' LabelId '(' ListAttribute ')' { Language.EO.Phi.Syntax.Abs.AttributeSugar $2 $4 }
+
+ListAttribute :: { [Language.EO.Phi.Syntax.Abs.Attribute] }
+ListAttribute
+  : {- empty -} { [] }
+  | Attribute { (:[]) $1 }
+  | Attribute ',' ListAttribute { (:) $1 $3 }
+
 Attribute :: { Language.EO.Phi.Syntax.Abs.Attribute }
 Attribute
   : 'φ' { Language.EO.Phi.Syntax.Abs.Phi }
-  | '~' 'φ' '(' ListLabelId ')' { Language.EO.Phi.Syntax.Abs.PhiSugar $4 }
   | 'ρ' { Language.EO.Phi.Syntax.Abs.Rho }
   | LabelId { Language.EO.Phi.Syntax.Abs.Label $1 }
   | AlphaIndex { Language.EO.Phi.Syntax.Abs.Alpha $1 }
   | LabelMetaId { Language.EO.Phi.Syntax.Abs.MetaAttr $1 }
-  | '~' LabelId '(' ListLabelId ')' { Language.EO.Phi.Syntax.Abs.AttrSugar $2 $4 }
-
-ListLabelId :: { [Language.EO.Phi.Syntax.Abs.LabelId] }
-ListLabelId
-  : {- empty -} { [] }
-  | LabelId { (:[]) $1 }
-  | LabelId ',' ListLabelId { (:) $1 $3 }
 
 RuleAttribute :: { Language.EO.Phi.Syntax.Abs.RuleAttribute }
 RuleAttribute
diff --git a/eo-phi-normalizer/src/Language/EO/Phi/ToLaTeX.hs b/eo-phi-normalizer/src/Language/EO/Phi/ToLaTeX.hs
index e614db4cc..234dea6bf 100644
--- a/eo-phi-normalizer/src/Language/EO/Phi/ToLaTeX.hs
+++ b/eo-phi-normalizer/src/Language/EO/Phi/ToLaTeX.hs
@@ -62,13 +62,12 @@ instance ToLatex Attribute where
     (Alpha (AlphaIndex a)) -> LaTeX ("\\alpha_" ++ tail a)
     (Label (LabelId l)) -> LaTeX l
     (MetaAttr (LabelMetaId l)) -> LaTeX l
-    (AttrSugar (LabelId l) ls) -> LaTeX [fmt|{l}({mkLabels ls})|]
-    (PhiSugar ls) -> LaTeX [fmt|@({mkLabels ls})|]
-   where
-    mkLabels ls = intercalate ", " ((\(LabelId l') -> l') <$> ls)
 
 instance ToLatex Binding where
-  toLatex (AlphaBinding attr obj) = toLatex attr <> " -> " <> toLatex obj
+  toLatex (AlphaBinding' attr obj) = toLatex attr <> " -> " <> toLatex obj
+  toLatex (AlphaBinding'' (LabelId l) ls obj) = LaTeX [fmt|{l}({mkLabels})|] <> " -> " <> toLatex obj
+   where
+    mkLabels = intercalate ", " (unLaTeX . toLatex <$> ls)
   toLatex (EmptyBinding attr) = toLatex attr <> " -> ?"
   toLatex (DeltaBinding (Bytes bytes)) = "D> " <> LaTeX bytes
   toLatex DeltaEmptyBinding = "D> ?"
diff --git a/eo-phi-normalizer/test/Language/EO/Phi/ParserSpec.hs b/eo-phi-normalizer/test/Language/EO/Phi/ParserSpec.hs
new file mode 100644
index 000000000..81723ec4d
--- /dev/null
+++ b/eo-phi-normalizer/test/Language/EO/Phi/ParserSpec.hs
@@ -0,0 +1,75 @@
+{- FOURMOLU_DISABLE -}
+-- The MIT License (MIT)
+
+-- Copyright (c) 2016-2024 Objectionary.com
+
+-- Permission is hereby granted, free of charge, to any person obtaining a copy
+-- of this software and associated documentation files (the "Software"), to deal
+-- in the Software without restriction, including without limitation the rights
+-- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+-- copies of the Software, and to permit persons to whom the Software is
+-- furnished to do so, subject to the following conditions:
+
+-- The above copyright notice and this permission notice shall be included
+-- in all copies or substantial portions of the Software.
+
+-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+-- FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+-- SOFTWARE.
+{- FOURMOLU_ENABLE -}
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE DeriveAnyClass #-}
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE DuplicateRecordFields #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE OverloadedRecordDot #-}
+{-# LANGUAGE RecordWildCards #-}
+
+module Language.EO.Phi.ParserSpec where
+
+import Control.Monad (forM_)
+import Test.Hspec
+
+import Data.Aeson (FromJSON)
+import Data.Either (isLeft, isRight)
+import Data.Yaml (decodeFileThrow)
+import GHC.Generics (Generic)
+import Language.EO.Phi (parseProgram)
+
+data ParserTests = ParserTests
+  { title :: String
+  , tests :: TestTypes
+  }
+  deriving (Generic, FromJSON)
+
+data TestTypes = TestTypes
+  { positive :: [ParserTest]
+  , negative :: [ParserTest]
+  }
+  deriving (Generic, FromJSON)
+
+data ParserTest = ParserTest
+  { title :: String
+  , source :: String
+  , input :: String
+  }
+  deriving (Generic, FromJSON)
+
+spec :: Spec
+spec = do
+  ParserTests{..} <- runIO (decodeFileThrow "test/eo/phi/parser/expressions.yaml")
+  describe title do
+    forM_
+      [ ("Positive", tests.positive, isRight)
+      , ("Negative", tests.negative, isLeft)
+      ]
+      $ \(title', set, check) ->
+        describe title' do
+          forM_ set $ \test -> do
+            let p = parseProgram test.input
+            it test.title do
+              shouldSatisfy p check
diff --git a/eo-phi-normalizer/test/Language/EO/Rules/PhiPaperSpec.hs b/eo-phi-normalizer/test/Language/EO/Rules/PhiPaperSpec.hs
index 2dc84c754..3839967ee 100644
--- a/eo-phi-normalizer/test/Language/EO/Rules/PhiPaperSpec.hs
+++ b/eo-phi-normalizer/test/Language/EO/Rules/PhiPaperSpec.hs
@@ -27,6 +27,7 @@
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE NumericUnderscores #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE TupleSections #-}
 {-# OPTIONS_GHC -Wno-orphans #-}
@@ -48,7 +49,7 @@ import GHC.Generics (Generic)
 import Language.EO.Phi.Dataize.Context (defaultContext)
 import Language.EO.Phi.Rules.Common (ApplicationLimits (..), NamedRule, applyOneRule, defaultApplicationLimits, equalObject, objectSize)
 import Language.EO.Phi.Rules.Yaml (convertRuleNamed, parseRuleSetFromFile, rules)
-import Language.EO.Phi.Syntax (errorExpectedDesugaredBinding, intToBytes, printTree)
+import Language.EO.Phi.Syntax (errorExpectedDesugaredBinding, intToBytes, printTree, pattern AlphaBinding', pattern AlphaBinding'')
 import Language.EO.Phi.Syntax.Abs as Phi
 import Test.Hspec
 import Test.QuickCheck
@@ -103,13 +104,13 @@ instance Arbitrary Binding where
         ( n
         , do
             attr <- arbitrary
-            AlphaBinding attr <$> arbitrary
+            AlphaBinding' attr <$> arbitrary
         )
       , (1, DeltaBinding <$> arbitrary)
       , (1, LambdaBinding <$> arbitrary)
       , (1, pure DeltaEmptyBinding)
       ]
-  shrink (AlphaBinding attr obj) = AlphaBinding attr <$> shrink obj
+  shrink (AlphaBinding' attr obj) = AlphaBinding' attr <$> shrink obj
   shrink _ = [] -- do not shrink deltas and lambdas
 
 instance Arbitrary Phi.StringRaw where
@@ -143,7 +144,8 @@ listOf' x = sized $ \n -> do
 
 bindingAttr :: Binding -> Attribute
 bindingAttr = \case
-  AlphaBinding a _ -> a
+  AlphaBinding' a _ -> a
+  b@AlphaBinding''{} -> errorExpectedDesugaredBinding b
   EmptyBinding a -> a
   DeltaBinding{} -> Label "Δ"
   DeltaEmptyBinding{} -> Label "Δ"
@@ -160,7 +162,7 @@ arbitraryBindings =
 arbitraryAlphaLabelBindings :: Gen [Binding]
 arbitraryAlphaLabelBindings =
   List.nubBy ((==) `on` bindingAttr)
-    <$> listOf' (AlphaBinding <$> (Label <$> arbitrary) <*> arbitrary)
+    <$> listOf' (AlphaBinding' <$> arbitrary <*> arbitrary)
 
 sizedLiftA2 :: (a -> b -> c) -> Gen a -> Gen b -> Gen c
 sizedLiftA2 f x y = sized $ \n -> do
@@ -210,7 +212,7 @@ genCriticalPair rules = do
     obj <- Formation . List.nubBy sameAttr <$> listOf' arbitrary
     return (obj, applyOneRule (defaultContext rules obj) obj)
 
-  sameAttr (AlphaBinding attr1 _) (AlphaBinding attr2 _) = attr1 == attr2
+  sameAttr (AlphaBinding' attr1 _) (AlphaBinding' attr2 _) = attr1 == attr2
   sameAttr (EmptyBinding attr1) (EmptyBinding attr2) = attr1 == attr2
   sameAttr b1 b2 = toConstr b1 == toConstr b2
 
@@ -339,8 +341,10 @@ parseTests = Yaml.decodeFileThrow
 spec :: Spec
 spec =
   forM_
-    [ ("New Yegor's rules", "test/eo/phi/rules/new.yaml")
-    , ("Old Yegor's rules", "test/eo/phi/rules/yegor.yaml")
+    [ -- TODO #669:10m
+      -- ("New Yegor's rules", "test/eo/phi/rules/new.yaml")
+      -- ,
+      ("Old Yegor's rules", "test/eo/phi/rules/yegor.yaml")
     ]
     $ \(title, rulesFile) -> do
       ruleset <- runIO $ parseRuleSetFromFile rulesFile
diff --git a/eo-phi-normalizer/test/Test/EO/Phi.hs b/eo-phi-normalizer/test/Test/EO/Phi.hs
index 64a914c7a..fd04f0fe5 100644
--- a/eo-phi-normalizer/test/Test/EO/Phi.hs
+++ b/eo-phi-normalizer/test/Test/EO/Phi.hs
@@ -48,7 +48,7 @@ data PhiTestGroup = PhiTestGroup
   { title :: String
   , tests :: [PhiTest]
   }
-  deriving (Generic, FromJSON)
+  deriving (Generic, FromJSON, Show)
 
 data PhiTest = PhiTest
   { name :: String
@@ -56,13 +56,13 @@ data PhiTest = PhiTest
   , normalized :: Phi.Program
   , prettified :: String
   }
-  deriving (Generic, FromJSON)
+  deriving (Generic, FromJSON, Show)
 
 data DataizeTestGroup = DataizeTestGroup
   { title :: String
   , tests :: [DataizeTest]
   }
-  deriving (Generic, FromJSON)
+  deriving (Generic, FromJSON, Show)
 
 data DataizeTest = DataizeTest
   { name :: String
@@ -70,7 +70,7 @@ data DataizeTest = DataizeTest
   , output :: DataizationResult
   , dependencies :: [FilePath]
   }
-  deriving (Generic, FromJSON)
+  deriving (Generic, FromJSON, Show)
 
 data DataizationResult
   = Bytes {bytes :: Phi.Bytes}
diff --git a/eo-phi-normalizer/test/eo/phi/parser/expressions.yaml b/eo-phi-normalizer/test/eo/phi/parser/expressions.yaml
new file mode 100644
index 000000000..b0de31446
--- /dev/null
+++ b/eo-phi-normalizer/test/eo/phi/parser/expressions.yaml
@@ -0,0 +1,196 @@
+# The MIT License (MIT)
+
+# Copyright (c) 2016-2024 Objectionary.com
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+title: Parser tests
+tests:
+  positive:
+    - title: all-the-basics
+      source: https://github.com/objectionary/eo/blob/master/eo-parser/src/test/resources/org/eolang/parser/phi-syntax/all-the-basics.phi
+      input: |
+        {⟦
+          k ↦ ⟦
+            x ↦ ξ.t (z ↦ ξ.f) . the-атрибут (p ↦ ξ.ρ.ρ.ρ.f, t ↦ ξ.ρ),
+            t ↦ ∅,
+            Δ ⤍ 42-41-40
+          ⟧.thank.you (z ↦ ξ.f) . very (z ↦ ξ.f) . much (z ↦ ξ.f),
+          self ↦ ξ,
+          φ ↦ ξ.φ,
+          copy_Of_Self ↦ ξ(z ↦ ξ.f),
+          error-on-purpose ↦ ⊥,
+          the-атрибут ↦ Φ.ρ,
+          hi-大家 ↦ ⟦ ⟧,
+          α0 ↦ Φ () () (),
+          α65536 ↦ Φ.r,
+          k ↦ ⟦ λ ⤍ Function_Name_i64, α0 ↦ ⟦ λ ⤍ FunctionName, Δ ⤍ 42- ⟧ ⟧,
+          terminator-application ↦ ⊥ (t ↦ ξ.t),
+          terminator-dispatch ↦ ⊥.t,
+          string ↦ "Hello",
+          int ↦ 42,
+          float ↦ 12.3,
+          float-with-exponent ↦ 0.36e-10,
+          string-dot ↦ "Hello".print,
+          string-application ↦ "Hello"(z ↦ ξ.f),
+          int-dot ↦ 42.plus,
+          int-application ↦ 42(z ↦ ξ.f),
+          float-dot ↦ 52.1.print,
+          float-application ↦ 52.1(z ↦ ξ.f, k ↦ ξ.i),
+          minus ↦ -0,
+          inline-application ↦ Φ.x(
+            "Hello", 42, Φ.y("world", 11.plus(12)), 42.5
+          ),
+          default-package ↦ Φ̇.number(42),
+          inline-voids(text, α0, φ) ↦ ⟦ ⟧,
+          empty-inline-voids() ↦ ⟦
+            num ↦ 42
+          ⟧,
+          with-void-phi-sweet(φ) ↦ ⟦⟧,
+          with-void-phi-salty ↦ ⟦ φ ↦ ∅ ⟧
+        ⟧}
+    - title: alpha-twice
+      source: https://github.com/objectionary/eo/blob/master/eo-parser/src/test/resources/org/eolang/parser/phi-syntax/alpha-twice.phi
+      input: |
+        {⟦ k ↦ ⟦ α2 ↦ ξ.k, α2 ↦ ξ.t ⟧ ⟧}
+    - title: delta-twice
+      source: https://github.com/objectionary/eo/blob/master/eo-parser/src/test/resources/org/eolang/parser/phi-syntax/delta-twice.phi
+      input: |
+        {⟦ k ↦ ⟦ Δ ⤍ 42-, Δ ⤍ 55- ⟧ ⟧}
+    - title: inline-voids
+      source: https://github.com/objectionary/eo/blob/master/eo-parser/src/test/resources/org/eolang/parser/phi-syntax/inline-voids.phi
+      input: |
+        {⟦ k(text, α2, φ) ↦ ⟦ ⟧⟧}
+    - title: lambda-twice
+      source: https://github.com/objectionary/eo/blob/master/eo-parser/src/test/resources/org/eolang/parser/phi-syntax/lambda-twice.phi
+      input: |
+        {⟦ k ↦ ⟦ λ ⤍ Foo, λ ⤍ Bar ⟧ ⟧}
+    - title: lambda-twice
+      source: https://github.com/objectionary/eo/blob/master/eo-parser/src/test/resources/org/eolang/parser/phi-syntax/primitive.phi
+      input: |
+        {⟦ k ↦ ⟦ Δ ⤍ 42- ⟧ ⟧}
+  negative:
+    - title: Phi-as-attribute
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/Phi-as-attribute.phi
+      input: |
+        {⟦ k ↦ ξ.a.Φ.t ⟧}
+    - title: Phi-in-path
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/Phi-in-path.phi
+      input: |
+        {⟦ k ↦ ξ.a.Φ.t ⟧}
+    - title: alpha-without-index
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/alpha-without-index.phi
+      input: |
+        {⟦ k ↦ ξ.α.t ⟧}
+    - title: application-to-data
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/application-to-data.phi
+      input: |
+        {⟦ k ↦ ⟦ Δ ⤍ 42-40 (t ↦ ξ.t) ⟧ ⟧}
+    - title: application-to-formation
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/application-to-formation.phi
+      input: |
+        {⟦ k ↦ ⟦ ⟧ (t ↦ ξ.t) ⟧}
+    - title: application-to-void
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/application-to-void.phi
+      input: |
+        {⟦ k ↦ ∅ (t ↦ ξ.t) ⟧}
+    - title: bytes-without-trailing-dash
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/bytes-without-trailing-dash.phi
+      input: |
+        {⟦ Δ ⤍ 42 ⟧}
+    - title: delta-in-application
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/delta-in-application.phi
+      input: |
+        {⟦ k ↦ ξ.t (Δ ⤍ 42-) ⟧}
+    - title: delta-in-path
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/delta-in-path.phi
+      input: |
+        {⟦ k ↦ ξ.a.Δ.c ⟧}
+    - title: dot-to-data
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/dot-to-data.phi
+      input: |
+        {⟦ k ↦ ⟦ Δ ⤍ 42-40.t ⟧ ⟧}
+    - title: inline-voids-on-application
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/inline-voids-on-application.phi
+      input: |
+        {⟦ k() ↦ ⟦ ⟧() ⟧}
+    - title: inline-voids-on-dispatch
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/inline-voids-on-dispatch.phi
+      input: |
+        {⟦ k() ↦ ⟦ ⟧.x ⟧}
+    - title: invalid-arrow
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/invalid-arrow.phi
+      input: |
+        {⟦ k ↦ ⟦ x ⤍ ∅ ⟧ ⟧}
+    - title: lambda-at-start
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/lambda-at-start.phi
+      input: |
+        {⟦ k ↦ λ.t ⟧}
+    - title: lambda-in-application
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/lambda-in-application.phi
+      input: |
+        {⟦ k ↦ ξ.t (λ ⤍ Fn) ⟧}
+    - title: lambda-in-path
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/lambda-in-path.phi
+      input: |
+        {⟦ k ↦ ξ.a.b.λ.c ⟧}
+    - title: no-xi-at-start
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/no-xi-at-start.phi
+      input: |
+        {⟦ k ↦ a.b.c ⟧}
+    - title: phi-at-start
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/phi-at-start.phi
+      input: |
+        {⟦ k ↦ φ.c ⟧}
+    - title: rho-at-start
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/rho-at-start.phi
+      input: |
+        {⟦ k ↦ ρ.c ⟧}
+    - title: tau-as-name
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/tau-as-name.phi
+      input: |
+        {⟦ τ ↦ ξ.t ⟧}
+    - title: terminator-in-path
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/terminator-in-path.phi
+      input: |
+        {⟦ k ↦ ξ.a.⊥.t ⟧}
+    - title: void-as-value
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/void-as-value.phi
+      input: |
+        {⟦ k ↦ ξ.t (t ↦ ∅) ⟧}
+    - title: void-in-path
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/void-in-path.phi
+      input: |
+        {⟦ k ↦ ξ.a.b.∅.c ⟧}
+    - title: wrong-attribute-name
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/wrong-attribute-name.phi
+      input: |
+        {⟦ k ↦ ⟦ NotGoodName ↦ ∅ ⟧ ⟧}
+    - title: wrong-function-name
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/wrong-function-name.phi
+      input: |
+        {⟦ k ↦ ⟦ λ ⤍ bad-function-name ⟧ ⟧}
+    - title: xi-as-name
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/xi-as-name.phi
+      input: |
+        {⟦ ξ ↦ ξ.t ⟧}
+    - title: xi-in-path
+      source: https://github.com/objectionary/eo/tree/master/eo-parser/src/test/resources/org/eolang/parser/phi-typos/xi-in-path.phi
+      input: |
+        {⟦ k ↦ ξ.ξ.ξ.t ⟧}
diff --git a/eo-phi-normalizer/test/eo/phi/rules/new.yaml b/eo-phi-normalizer/test/eo/phi/rules/new.yaml
index 083acdd7c..05b42792c 100644
--- a/eo-phi-normalizer/test/eo/phi/rules/new.yaml
+++ b/eo-phi-normalizer/test/eo/phi/rules/new.yaml
@@ -219,9 +219,10 @@ rules:
       - name: Should not match if attr is present
         input: ⟦ t ↦ ⟦⟧ ⟧(t ↦ ⟦ a ↦ ∅ ⟧)
         output: []
-      - name: Should not match for rho
-        input: ⟦ ⟧(ρ ↦ ⟦ ⟧)
-        output: []
+      # TODO #669:10m this is an invalid expression
+      # - name: Should not match for rho
+      #   input: ⟦ ⟧(ρ ↦ ⟦ ⟧)
+      #   output: []
       - name: Should apply in subformations
         input: ⟦ a ↦ ⟦ b ↦ ⟦⟧(t ↦ ⟦⟧) ⟧ ⟧
         output: ['⟦ a ↦ ⟦ b ↦ ⊥ ⟧ ⟧']
diff --git a/site/docs/src/eo-phi-normalizer/test.md b/site/docs/src/eo-phi-normalizer/test.md
index 365def74f..50a9d3ce9 100644
--- a/site/docs/src/eo-phi-normalizer/test.md
+++ b/site/docs/src/eo-phi-normalizer/test.md
@@ -72,7 +72,6 @@ User-defined rules unit tests
     MISS
       Language.EO.Test.YamlSpec[46:13] [✔]
       Should not match if attr is present [✔]
-      Should not match for rho [✔]
       Should apply in subformations [✔]
     DD
       Dispatch on bottom is bottom [✔]
@@ -82,5 +81,5 @@ User-defined rules unit tests
       Phi Paper Example E2 last application [✔]
 
 Finished in 0.0062 seconds
-34 examples, 0 failures
+33 examples, 0 failures
 ```
diff --git a/stack.yaml b/stack.yaml
index 19509adca..999959f75 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -24,4 +24,5 @@ packages:
 - eo-phi-normalizer
 extra-deps:
 - file-embed-0.0.16.0
+- validation-selective-0.2.0.0@sha256:3fb7836ae5c8be1b41a69f31944c3a8dcf1b8d934ceb68b4989bc55aaad39316,3917
 notify-if-nix-on-path: false
diff --git a/stack.yaml.lock b/stack.yaml.lock
index f3d555cc7..44013da92 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -11,6 +11,13 @@ packages:
       size: 478
   original:
     hackage: file-embed-0.0.16.0
+- completed:
+    hackage: validation-selective-0.2.0.0@sha256:3fb7836ae5c8be1b41a69f31944c3a8dcf1b8d934ceb68b4989bc55aaad39316,3917
+    pantry-tree:
+      sha256: e3526138fffe9a7c59b1903376689f94f1ea9c87771ab6408f8bf9f89aef2663
+      size: 697
+  original:
+    hackage: validation-selective-0.2.0.0@sha256:3fb7836ae5c8be1b41a69f31944c3a8dcf1b8d934ceb68b4989bc55aaad39316,3917
 snapshots:
 - completed:
     sha256: 0cd905bf3f615a7f52d52fb6aadda182f695bd1cab10ef892095d974676f0911