[cfe] Disallow annotations on type parameters of function types

Also, do not copy annotations on type parameters of functions into
their inferred types.

See dart-lang/language#656

Change-Id: I1460007645a32ac56a505b23ab3ee8a457c3f994
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/123732
Commit-Queue: Aske Simon Christensen <[email protected]>
Reviewed-by: Erik Ernst <[email protected]>

Author: askeksa

pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart

@@ -102,6 +102,16 @@ Message _withArgumentsAccessError(String name) {
       message: """Access error: '${name}'.""", arguments: {'name': name});
 }
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeAnnotationOnFunctionTypeTypeVariable =
+    messageAnnotationOnFunctionTypeTypeVariable;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageAnnotationOnFunctionTypeTypeVariable =
+    const MessageCode("AnnotationOnFunctionTypeTypeVariable",
+        message:
+            r"""A type variable on a function type can't have annotations.""");
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeAnonymousBreakTargetOutsideFunction =
     messageAnonymousBreakTargetOutsideFunction;

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

@@ -3041,6 +3041,15 @@ class BodyBuilder extends ScopeListener<JumpTarget>
     FormalParameters formals = pop();
     UnresolvedType returnType = pop();
     List<TypeVariableBuilder> typeVariables = pop();
+    if (typeVariables != null) {
+      for (TypeVariableBuilder builder in typeVariables) {
+        if (builder.parameter.annotations.isNotEmpty) {
+          addProblem(fasta.messageAnnotationOnFunctionTypeTypeVariable,
+              builder.charOffset, builder.name.length);
+          builder.parameter.annotations = const <Expression>[];
+        }
+      }
+    }
     UnresolvedType type = formals.toFunctionType(
         returnType,
         libraryBuilder.nullableBuilderIfTrue(questionMark != null),

pkg/front_end/messages.status

@@ -13,6 +13,7 @@ AccessError/analyzerCode: Fail
 AccessError/example: Fail
 AmbiguousSupertypes/example: Fail
 AnnotationOnEnumConstant/example: Fail
+AnnotationOnFunctionTypeTypeVariable/analyzerCode: Fail
 AnonymousBreakTargetOutsideFunction/part_wrapped_statement: Fail
 AnonymousBreakTargetOutsideFunction/statement: Fail # Duplicated error as parser also complains.
 AnonymousContinueTargetOutsideFunction/part_wrapped_statement: Fail

pkg/front_end/messages.yaml

@@ -2061,6 +2061,11 @@ TypeVariableSameNameAsEnclosing:
   template: "A type variable can't have the same name as its enclosing declaration."
   analyzerCode: CONFLICTING_TYPE_VARIABLE_AND_CLASS
 
+AnnotationOnFunctionTypeTypeVariable:
+  template: "A type variable on a function type can't have annotations."
+  script:
+    - "main() { Function<@Object() T>() x; }"
+
 ExpectedEnumBody:
   template: "Expected a enum body, but got '#lexeme'."
   tip: "An enum definition must have a body with at least one constant name."

pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart

@@ -11,7 +11,7 @@ class Foo {
 
 void test() {
   void f<@Foo(/*@ typeArgs=String* */ const []) T>() {}
-  var /*@ type=<@Foo::•(const <String*>[]) T extends Object* = dynamic>() ->* Null? */ x =
+  var /*@ type=<T extends Object* = dynamic>() ->* Null? */ x =
       <@Foo(/*@ typeArgs=String* */ const []) T> /*@ returnType=Null? */ () {};
 }
 

pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.expect

@@ -9,7 +9,7 @@ class Foo extends core::Object {
 }
 static method test() → void {
   function f<@#C1 T extends core::Object* = dynamic>() → void {}
-  <@self::Foo::•(const <core::String*>[]) T extends core::Object* = dynamic>() →* core::Null? x = <@#C1 T extends core::Object* = dynamic>() → core::Null? {};
+  <T extends core::Object* = dynamic>() →* core::Null? x = <@#C1 T extends core::Object* = dynamic>() → core::Null? {};
 }
 static method main() → dynamic {}
 

pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.transformed.expect

@@ -9,7 +9,7 @@ class Foo extends core::Object {
 }
 static method test() → void {
   function f<@#C1 T extends core::Object* = dynamic>() → void {}
-  <@self::Foo::•(const <core::String*>[]) T extends core::Object* = dynamic>() →* core::Null? x = <@#C1 T extends core::Object* = dynamic>() → core::Null? {};
+  <T extends core::Object* = dynamic>() →* core::Null? x = <@#C1 T extends core::Object* = dynamic>() → core::Null? {};
 }
 static method main() → dynamic {}
 

pkg/kernel/lib/type_algebra.dart

@@ -4,7 +4,6 @@
 library kernel.type_algebra;
 
 import 'ast.dart';
-import 'clone.dart';
 
 /// Returns a type where all occurrences of the given type parameters have been
 /// replaced with the corresponding types.
@@ -117,7 +116,6 @@ FreshTypeParameters getFreshTypeParameters(List<TypeParameter> typeParameters) {
     map[typeParameters[i]] = new TypeParameterType.forAlphaRenaming(
         typeParameters[i], freshParameters[i]);
   }
-  CloneVisitor cloner;
   for (int i = 0; i < typeParameters.length; ++i) {
     TypeParameter typeParameter = typeParameters[i];
     TypeParameter freshTypeParameter = freshParameters[i];
@@ -128,16 +126,9 @@ FreshTypeParameters getFreshTypeParameters(List<TypeParameter> typeParameters) {
         : null;
     freshTypeParameter.variance =
         typeParameter.isLegacyCovariant ? null : typeParameter.variance;
-    if (typeParameter.annotations.isNotEmpty) {
-      // Annotations can't refer to type parameters, so the cloner shouldn't
-      // perform the substitution.
-      // TODO(dmitryas): Consider rewriting getFreshTypeParameters using cloner
-      // for copying typeParameters as well.
-      cloner ??= new CloneVisitor();
-      for (Expression annotation in typeParameter.annotations) {
-        freshTypeParameter.addAnnotation(cloner.clone(annotation));
-      }
-    }
+    // Annotations on a type parameter are specific to the declaration of the
+    // type parameter, rather than the type parameter as such, and therefore
+    // should not be copied here.
   }
   return new FreshTypeParameters(freshParameters, Substitution.fromMap(map));
 }

pkg/kernel/lib/verifier.dart

@@ -351,6 +351,10 @@ class VerifyingVisitor extends RecursiveVisitor<void> {
     declareTypeParameters(node.typeParameters);
     for (var typeParameter in node.typeParameters) {
       typeParameter.bound?.accept(this);
+      if (typeParameter.annotations.isNotEmpty) {
+        problem(
+            typeParameter, "Annotation on type parameter in function type.");
+      }
     }
     visitList(node.positionalParameters, this);
     visitList(node.namedParameters, this);