checker: fix alias to fixed array w/ size defined by constant

vlib/v/ast/ast.v

@@ -1452,13 +1452,14 @@ pub:
 
 pub struct AliasTypeDecl {
 pub:
-	name        string
-	is_pub      bool
-	typ         Type
+	name     string
+	is_pub   bool
+	typ      Type
+	pos      token.Pos
+	type_pos token.Pos
+	comments []Comment
+pub mut:
 	parent_type Type
-	pos         token.Pos
-	type_pos    token.Pos
-	comments    []Comment
 }
 
 // SumTypeDecl is the ast node for `type MySumType = string | int`

vlib/v/ast/types.v

@@ -96,9 +96,8 @@ pub fn pref_arch_to_table_language(pref_arch pref.Arch) Language {
 // See also: Table.sym.
 @[minify]
 pub struct TypeSymbol {
-pub:
-	parent_idx int
 pub mut:
+	parent_idx    int
 	info          TypeInfo
 	kind          Kind
 	name          string // the internal & source name of the type, i.e. `[5]int`.
@@ -211,10 +210,11 @@ pub:
 
 @[minify]
 pub struct Alias {
-pub:
+pub mut:
 	parent_type Type
-	language    Language
-	is_import   bool
+pub:
+	language  Language
+	is_import bool
 }
 
 pub struct Aggregate {

vlib/v/builder/builder.v

@@ -138,10 +138,10 @@ pub fn (mut b Builder) middle_stages() ! {
 	if b.checker.should_abort {
 		return error('too many errors/warnings/notices')
 	}
-	if b.checker.unresolved_return_size.len > 0 {
-		util.timing_start('Checker.update_unresolved_sizes')
-		b.checker.update_unresolved_return_sizes()
-		util.timing_measure('Checker.update_unresolved_sizes')
+	if b.checker.unresolved_fixed_sizes.len > 0 {
+		util.timing_start('Checker.update_unresolved_fixed_sizes')
+		b.checker.update_unresolved_fixed_sizes()
+		util.timing_measure('Checker.update_unresolved_fixed_sizes')
 	}
 	if b.pref.check_only {
 		return error_with_code('stop_after_checker', 8001)

vlib/v/checker/checker.v

@@ -74,21 +74,21 @@ pub mut:
 	in_for_count                int      // if checker is currently in a for loop
 	returns                     bool
 	scope_returns               bool
-	is_builtin_mod              bool          // true inside the 'builtin', 'os' or 'strconv' modules; TODO: remove the need for special casing this
-	is_just_builtin_mod         bool          // true only inside 'builtin'
-	is_generated                bool          // true for `@[generated] module xyz` .v files
-	unresolved_return_size      []&ast.FnDecl // funcs with unresolved array fixed size e.g. fn func() [const1]int
-	inside_recheck              bool          // true when rechecking rhs assign statement
-	inside_unsafe               bool          // true inside `unsafe {}` blocks
-	inside_const                bool          // true inside `const ( ... )` blocks
-	inside_anon_fn              bool          // true inside `fn() { ... }()`
-	inside_lambda               bool          // true inside `|...| ...`
-	inside_ref_lit              bool          // true inside `a := &something`
-	inside_defer                bool          // true inside `defer {}` blocks
-	inside_return               bool          // true inside `return ...` blocks
-	inside_fn_arg               bool          // `a`, `b` in `a.f(b)`
-	inside_ct_attr              bool          // true inside `[if expr]`
-	inside_x_is_type            bool          // true inside the Type expression of `if x is Type {`
+	is_builtin_mod              bool        // true inside the 'builtin', 'os' or 'strconv' modules; TODO: remove the need for special casing this
+	is_just_builtin_mod         bool        // true only inside 'builtin'
+	is_generated                bool        // true for `@[generated] module xyz` .v files
+	unresolved_fixed_sizes      []&ast.Stmt // funcs with unresolved array fixed size e.g. fn func() [const1]int
+	inside_recheck              bool        // true when rechecking rhs assign statement
+	inside_unsafe               bool        // true inside `unsafe {}` blocks
+	inside_const                bool        // true inside `const ( ... )` blocks
+	inside_anon_fn              bool        // true inside `fn() { ... }()`
+	inside_lambda               bool        // true inside `|...| ...`
+	inside_ref_lit              bool        // true inside `a := &something`
+	inside_defer                bool        // true inside `defer {}` blocks
+	inside_return               bool        // true inside `return ...` blocks
+	inside_fn_arg               bool        // `a`, `b` in `a.f(b)`
+	inside_ct_attr              bool        // true inside `[if expr]`
+	inside_x_is_type            bool        // true inside the Type expression of `if x is Type {`
 	inside_generic_struct_init  bool
 	inside_integer_literal_cast bool // true inside `int(123)`
 	cur_struct_generic_types    []ast.Type
@@ -613,7 +613,11 @@ fn (mut c Checker) alias_type_decl(node ast.AliasTypeDecl) {
 				'array')
 		}
 		.array_fixed {
-			c.check_alias_vs_element_type_of_parent(node, (parent_typ_sym.info as ast.ArrayFixed).elem_type,
+			array_fixed_info := parent_typ_sym.info as ast.ArrayFixed
+			if c.array_fixed_has_unresolved_size(array_fixed_info) {
+				c.unresolved_fixed_sizes << unsafe { &ast.TypeDecl(&node) }
+			}
+			c.check_alias_vs_element_type_of_parent(node, array_fixed_info.elem_type,
 				'fixed array')
 		}
 		.map {
@@ -5554,12 +5558,33 @@ fn (c &Checker) check_import_sym_conflict(ident string) bool {
 	return false
 }
 
-pub fn (mut c Checker) update_unresolved_return_sizes() {
-	for mut fun in c.unresolved_return_size {
-		ret_sym := c.table.sym(fun.return_type)
-		if ret_sym.info is ast.ArrayFixed && c.array_fixed_has_unresolved_size(ret_sym.info) {
-			mut size_expr := ret_sym.info.size_expr
-			fun.return_type = c.eval_array_fixed_sizes(mut size_expr, 0, ret_sym.info.elem_type)
+// update_unresolved_fixed_sizes updates the unresolved type symbols for array fixed return type and alias type
+pub fn (mut c Checker) update_unresolved_fixed_sizes() {
+	for mut stmt in c.unresolved_fixed_sizes {
+		if mut stmt is ast.FnDecl { // return types
+			ret_sym := c.table.sym(stmt.return_type)
+			if ret_sym.info is ast.ArrayFixed && c.array_fixed_has_unresolved_size(ret_sym.info) {
+				mut size_expr := ret_sym.info.size_expr
+				stmt.return_type = c.eval_array_fixed_sizes(mut size_expr, 0, ret_sym.info.elem_type)
+			}
+		} else if mut stmt is ast.TypeDecl { // alias
+			mut alias_decl := stmt
+			if mut alias_decl is ast.AliasTypeDecl {
+				alias_sym := c.table.sym(alias_decl.parent_type)
+				if alias_sym.info is ast.ArrayFixed
+					&& c.array_fixed_has_unresolved_size(alias_sym.info) {
+					mut size_expr := alias_sym.info.size_expr
+					alias_decl.parent_type = c.eval_array_fixed_sizes(mut size_expr, 0,
+						alias_sym.info.elem_type)
+
+					// overwriting current alias type
+					mut typ_sym := c.table.type_symbols[alias_decl.typ.idx()]
+					typ_sym.parent_idx = alias_decl.parent_type.idx()
+					if mut typ_sym.info is ast.Alias {
+						typ_sym.info.parent_type = alias_decl.parent_type
+					}
+				}
+			}
 		}
 	}
 }

vlib/v/checker/fn.v

@@ -171,7 +171,7 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 			}
 		}
 		if return_sym.info is ast.ArrayFixed && c.array_fixed_has_unresolved_size(return_sym.info) {
-			c.unresolved_return_size << node
+			c.unresolved_fixed_sizes << node
 		}
 
 		final_return_sym := c.table.final_sym(node.return_type)

vlib/v/tests/aliases/alias_const_array_fixed_test.v

@@ -0,0 +1,20 @@
+module main
+
+const image_width = 800
+const image_height = 400
+
+struct Colour {
+	r u8
+	g u8
+	b u8
+}
+
+const buffer_size = image_width * image_height * sizeof[Colour]()
+
+type ImageBuffer = [buffer_size]Colour
+
+fn test_main() {
+	println('Hello World!')
+	t := ImageBuffer{}
+	assert t.len == buffer_size
+}