parser: disallow having builtin type as type names for enum, sum type and alias (#19043)

vlib/v/parser/parser.v

@@ -4011,7 +4011,8 @@ fn (mut p Parser) enum_decl() ast.EnumDecl {
 		}
 		is_pub: is_pub
 	})
-	if idx == -1 {
+	if idx in [ast.invalid_type_idx, ast.string_type_idx, ast.rune_type_idx, ast.array_type_idx,
+		ast.map_type_idx] {
 		p.error_with_pos('cannot register enum `${name}`, another type with this name exists',
 			end_pos)
 	}
@@ -4109,7 +4110,8 @@ fn (mut p Parser) type_decl() ast.TypeDecl {
 			}
 			is_pub: is_pub
 		})
-		if typ == ast.invalid_type_idx {
+		if typ in [ast.invalid_type_idx, ast.string_type_idx, ast.rune_type_idx, ast.array_type_idx,
+			ast.map_type_idx] {
 			p.error_with_pos('cannot register sum type `${name}`, another type with this name exists',
 				name_pos)
 			return ast.SumTypeDecl{}
@@ -4149,7 +4151,8 @@ fn (mut p Parser) type_decl() ast.TypeDecl {
 		is_pub: is_pub
 	})
 	type_end_pos := p.prev_tok.pos()
-	if idx == ast.invalid_type_idx {
+	if idx in [ast.invalid_type_idx, ast.string_type_idx, ast.rune_type_idx, ast.array_type_idx,
+		ast.map_type_idx] {
 		p.error_with_pos('cannot register alias `${name}`, another type with this name exists',
 			name_pos)
 		return ast.AliasTypeDecl{}

vlib/v/parser/tests/builtin_alias_type_name_err.out

@@ -0,0 +1,3 @@
+vlib/v/parser/tests/builtin_alias_type_name_err.vv:1:6: error: cannot register alias `string`, another type with this name exists
+    1 | type string = int
+      |      ~~~~~~

vlib/v/parser/tests/builtin_alias_type_name_err.vv

@@ -0,0 +1 @@
+type string = int

vlib/v/parser/tests/builtin_enum_type_name_err.out

@@ -0,0 +1,5 @@
+vlib/v/parser/tests/builtin_enum_type_name_err.vv:1:6: error: cannot register enum `rune`, another type with this name exists
+    1 | enum rune {
+      |      ~~~~
+    2 |     a
+    3 |     b

vlib/v/parser/tests/builtin_enum_type_name_err.vv

@@ -0,0 +1,5 @@
+enum rune {
+	a
+	b
+	c
+}

vlib/v/parser/tests/builtin_sum_type_type_name_err.out

@@ -0,0 +1,3 @@
+vlib/v/parser/tests/builtin_sum_type_type_name_err.vv:1:6: error: cannot register sum type `map`, another type with this name exists
+    1 | type map = int | u64
+      |      ~~~

vlib/v/parser/tests/builtin_sum_type_type_name_err.vv

@@ -0,0 +1 @@
+type map = int | u64