[cfe] Support typedefs in object patterns

Part of #49749

Change-Id: I0d29a875a6a0d3bac5c20309a1b4a6c8b48618f5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/277960
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Chloe Stefantsova <[email protected]>

Author: chloestefantsova

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

@@ -8347,8 +8347,37 @@ class BodyBuilder extends StackListenerImpl
     // TODO(cstefantsova): Handle the case of secondIdentifier != null
     handleIdentifier(firstIdentifier, IdentifierContext.typeReference);
     Object? resolvedIdentifier = pop();
+
     if (resolvedIdentifier is TypeUseGenerator) {
       TypeDeclarationBuilder typeDeclaration = resolvedIdentifier.declaration;
+
+      if (typeDeclaration is TypeAliasBuilder) {
+        if (typeArguments == null ||
+            typeArguments.length ==
+                typeDeclaration.typedef.typeParameters.length) {
+          TypeDeclarationBuilder? unaliasedTypeDeclaration =
+              typeDeclaration.unaliasDeclaration(typeArguments);
+          List<TypeBuilder>? unaliasedTypeArguments =
+              typeDeclaration.unaliasTypeArguments(typeArguments);
+          if (unaliasedTypeDeclaration == null) {
+            // TODO(cstefantsova): Make sure an error is reported elsewhere.
+            push(new DummyPattern(firstIdentifier.charOffset));
+            return;
+          } else {
+            typeDeclaration = unaliasedTypeDeclaration;
+            typeArguments = unaliasedTypeArguments;
+          }
+        } else {
+          addProblem(
+              fasta.templateTypeArgumentMismatch
+                  .withArguments(typeDeclaration.typedef.typeParameters.length),
+              firstIdentifier.charOffset,
+              noLength);
+          push(new DummyPattern(firstIdentifier.charOffset));
+          return;
+        }
+      }
+
       if (typeDeclaration is ClassBuilder) {
         List<DartType>? builtTypeArguments;
         if (typeArguments != null) {
@@ -8359,7 +8388,13 @@ class BodyBuilder extends StackListenerImpl
                   .add(typeBuilder.build(libraryBuilder, TypeUse.typeArgument));
             }
           } else {
-            // TODO(cstefantsova): Report an error.
+            addProblem(
+                fasta.templateTypeArgumentMismatch
+                    .withArguments(typeDeclaration.cls.typeParameters.length),
+                firstIdentifier.charOffset,
+                noLength);
+            push(new DummyPattern(firstIdentifier.charOffset));
+            return;
           }
         }
         push(new ObjectPattern(
@@ -8368,7 +8403,7 @@ class BodyBuilder extends StackListenerImpl
             builtTypeArguments,
             firstIdentifier.offset));
       } else {
-        // TODO(cstefantsova): Handle this case.
+        // TODO(cstefantsova): Handle other possibilities.
         push(new DummyPattern(firstIdentifier.charOffset));
       }
     } else {

pkg/front_end/testcases/patterns/object_pattern_errors.dart

@@ -0,0 +1,14 @@
+// Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class A {}
+
+typedef B<X> = A;
+
+test(dynamic x) {
+  if (x case A<int>()) {} // Error.
+  if (x case B()) {} // Ok: the type argument is inferred.
+  if (x case B<int>()) {} // Ok.
+  if (x case B<String, num>()) {} // Error.
+}

pkg/front_end/testcases/patterns/object_pattern_errors.dart.strong.expect

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();

pkg/front_end/testcases/patterns/object_pattern_errors.dart.strong.transformed.expect

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();

pkg/front_end/testcases/patterns/object_pattern_errors.dart.textual_outline.expect

@@ -0,0 +1,4 @@
+class A {}
+
+typedef B<X> = A;
+test(dynamic x) {}

pkg/front_end/testcases/patterns/object_pattern_errors.dart.textual_outline_modelled.expect

@@ -0,0 +1,4 @@
+class A {}
+
+test(dynamic x) {}
+typedef B<X> = A;

pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.expect

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();

pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.modular.expect

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();

pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.outline.expect

@@ -0,0 +1,13 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    ;
+}
+static method test(dynamic x) → dynamic
+  ;
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();

pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.transformed.expect

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();

pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart

@@ -0,0 +1,52 @@
+// Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class A {
+  int foo;
+
+  A(this.foo);
+}
+
+typedef B = A;
+
+class C<X, Y> {
+  X x;
+  Y y;
+
+  C(this.x, this.y);
+}
+
+typedef D<X> = C<X, X>;
+
+test1(dynamic x) {
+  if (x case B(:var foo)) {
+    return foo;
+  } else {
+    return null;
+  }
+}
+
+test2(dynamic x) {
+  if (x case D<String>(:var x)) {
+    return x;
+  } else {
+    return null;
+  }
+}
+
+main() {
+  expectEquals(0, test1(new A(0)));
+  expectEquals(1, test1(new B(1)));
+  expectEquals(null, test1(null));
+
+  expectEquals("one", test2(new C("one", "two")));
+  expectEquals("one", test2(new D("one", "two")));
+  expectEquals(null, test2(null));
+}
+
+expectEquals(x, y) {
+  if (x != y) {
+    throw "Expected ${x} to be equal to ${y}.";
+  }
+}