poc: add Decimal[bits, places] syntax

vyper/semantics/analysis/utils.py

@@ -22,7 +22,7 @@
 from vyper.semantics.namespace import get_namespace
 from vyper.semantics.types.base import TYPE_T, VyperType
 from vyper.semantics.types.bytestrings import BytesT, StringT
-from vyper.semantics.types.primitives import AddressT, BoolT, BytesM_T, IntegerT
+from vyper.semantics.types.primitives import AddressT, BoolT, BytesM_T, IntegerT, DecimalT
 from vyper.semantics.types.subscriptable import DArrayT, SArrayT, TupleT
 from vyper.utils import checksum_encode, int_to_fourbytes
 
@@ -303,7 +303,7 @@ def types_from_Constant(self, node):
                 # special handling for bytestrings since their
                 # class objects are in the type map, not the type itself
                 # (worth rethinking this design at some point.)
-                if t in (BytesT, StringT):
+                if t in (BytesT, StringT, DecimalT):
                     t = t.from_literal(node)
 
                 # any more validation which needs to occur

vyper/semantics/types/__init__.py

@@ -9,7 +9,7 @@
 
 
 def _get_primitive_types():
-    res = [BoolT(), DecimalT()]
+    res = [BoolT()]
 
     res.extend(IntegerT.all())
     res.extend(BytesM_T.all())
@@ -21,6 +21,8 @@ def _get_primitive_types():
     # note: since bytestrings are parametrizable, the *class* objects
     # are in the namespace instead of concrete type objects.
     res.extend([BytesT, StringT])
+    # ditto for Decimals
+    res.append(DecimalT)
 
     ret = {t._id: t for t in res}
     ret.update(_get_sequence_types())

vyper/semantics/types/primitives.py

@@ -10,6 +10,7 @@
     CompilerPanic,
     InvalidLiteral,
     InvalidOperation,
+    InvalidType, UnimplementedException,
     OverflowException,
     VyperException,
 )
@@ -313,9 +314,7 @@ def SINT(bits):
 class DecimalT(NumericT):
     typeclass = "decimal"
 
-    _bits = 168  # TODO generalize
-    _decimal_places = 10  # TODO generalize
-    _id = "decimal"
+    _id = "Decimal"
     _is_signed = True
     _invalid_ops = (
         vy_ast.Pow,
@@ -331,6 +330,43 @@ class DecimalT(NumericT):
 
     ast_type = Decimal
 
+    def __init__(self, bits=168, decimal_places=10):
+        self._bits = bits
+        self._decimal_places = decimal_places
+
+        if bits != 168 or decimal_places != 10:
+            raise UnimplementedException("Not implemented: {repr(self)}", hint="only Decimal[168, 10] is currently available")
+
+    def __repr__(self):
+        return f"Decimal[{self._bits}, {self._decimal_places}]"
+
+    @classmethod
+    def from_annotation(cls, node):
+        def _fail():
+            raise InvalidType("not a valid Decimal", hint="expected: Decimal[<bits>, <places}")
+
+        if not isinstance(node, vy_ast.Subscript):
+            _fail()
+        if not isinstance(node.slice, vy_ast.Tuple):
+            _fail()
+        if len(node.slice.elements) != 2:
+            _fail()
+        bits = node.slice.elements[0].get_folded_value().value
+        places = node.slice.elements[1].get_folded_value().value
+        if not isinstance(bits, int) or not isinstance(places, int):
+            _fail()
+
+        return cls(bits, places)
+
+    def validate_literal(self, node) -> None:
+        if not isinstance(node, vy_ast.Decimal):
+            # TODO: check bits, places
+            raise TypeMismatch("Not a decimal")
+
+    @classmethod
+    def from_literal(cls, node):
+        return DecimalT(168, 10)
+
     def validate_numeric_op(self, node) -> None:
         try:
             super().validate_numeric_op(node)

vyper/semantics/types/utils.py

@@ -101,7 +101,7 @@ def _type_from_annotation(node: vy_ast.VyperNode) -> VyperType:
 
     if isinstance(node, vy_ast.Subscript):
         # ex. HashMap, DynArray, Bytes, static arrays
-        if node.value.get("id") in ("HashMap", "Bytes", "String", "DynArray"):
+        if node.value.get("id") in ("HashMap", "Bytes", "String", "DynArray", "Decimal"):
             assert isinstance(node.value, vy_ast.Name)  # mypy hint
             type_ctor = namespace[node.value.id]
         else: