DevX. Issue 22915. Show instantiated type alias in diagnostics.

Bug: #22915
Change-Id: I733bcb6021a167825840027df371fd22cfc71ce3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/370701
Reviewed-by: Sam Rawlins <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

pkg/analyzer/lib/error/listener.dart

@@ -11,6 +11,7 @@ import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/diagnostic/diagnostic.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/source/source.dart';
+import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/diagnostic/diagnostic.dart';
 import 'package:meta/meta.dart';
 import 'package:source_span/source_span.dart';
@@ -340,8 +341,10 @@ class ErrorReporter {
     Map<String, List<_TypeToConvert>> typeGroups = {};
     for (int i = 0; i < arguments.length; i++) {
       var argument = arguments[i];
-      if (argument is DartType) {
-        String displayName = argument.getDisplayString();
+      if (argument is TypeImpl) {
+        String displayName = argument.getDisplayString(
+          preferTypeAlias: true,
+        );
         List<_TypeToConvert> types =
             typeGroups.putIfAbsent(displayName, () => <_TypeToConvert>[]);
         types.add(_TypeToConvert(i, argument, displayName));

pkg/analyzer/lib/src/dart/element/display_string_builder.dart

@@ -21,10 +21,14 @@ class ElementDisplayStringBuilder {
   /// Whether to allow a display string to be written in multiple lines.
   final bool _multiline;
 
+  /// Whether to write instantiated type alias when available.
+  final bool preferTypeAlias;
+
   ElementDisplayStringBuilder({
     @Deprecated('Only non-nullable by default mode is supported')
     bool withNullability = true,
     bool multiline = false,
+    required this.preferTypeAlias,
   })  : _withNullability = withNullability,
         _multiline = multiline;
 
@@ -179,6 +183,10 @@ class ElementDisplayStringBuilder {
   }
 
   void writeFunctionType(FunctionType type) {
+    if (_maybeWriteTypeAlias(type)) {
+      return;
+    }
+
     type = _uniqueTypeParameters(type);
 
     _writeType(type.returnType);
@@ -201,6 +209,10 @@ class ElementDisplayStringBuilder {
   }
 
   void writeInterfaceType(InterfaceType type) {
+    if (_maybeWriteTypeAlias(type)) {
+      return;
+    }
+
     _write(type.element.name);
     _writeTypeArguments(type.typeArguments);
     _writeNullability(type.nullabilitySuffix);
@@ -245,6 +257,10 @@ class ElementDisplayStringBuilder {
   }
 
   void writeRecordType(RecordType type) {
+    if (_maybeWriteTypeAlias(type)) {
+      return;
+    }
+
     var positionalFields = type.positionalFields;
     var namedFields = type.namedFields;
     var fieldCount = positionalFields.length + namedFields.length;
@@ -355,6 +371,18 @@ class ElementDisplayStringBuilder {
     _write('void');
   }
 
+  bool _maybeWriteTypeAlias(DartType type) {
+    if (preferTypeAlias) {
+      if (type.alias case var alias?) {
+        _write(alias.element.name);
+        _writeTypeArguments(alias.typeArguments);
+        _writeNullability(type.nullabilitySuffix);
+        return true;
+      }
+    }
+    return false;
+  }
+
   void _write(String str) {
     _buffer.write(str);
   }

pkg/analyzer/lib/src/dart/element/element.dart

@@ -2486,9 +2486,11 @@ abstract class ElementImpl implements Element {
     @Deprecated('Only non-nullable by default mode is supported')
     bool withNullability = true,
     bool multiline = false,
+    bool preferTypeAlias = false,
   }) {
     var builder = ElementDisplayStringBuilder(
       multiline: multiline,
+      preferTypeAlias: preferTypeAlias,
     );
     appendTo(builder);
     return builder.toString();

pkg/analyzer/lib/src/dart/element/member.dart

@@ -713,9 +713,11 @@ abstract class Member implements Element {
     @Deprecated('Only non-nullable by default mode is supported')
     bool withNullability = true,
     bool multiline = false,
+    bool preferTypeAlias = false,
   }) {
     var builder = ElementDisplayStringBuilder(
       multiline: multiline,
+      preferTypeAlias: preferTypeAlias,
     );
     appendTo(builder);
     return builder.toString();

pkg/analyzer/lib/src/dart/element/type.dart

@@ -1342,10 +1342,12 @@ abstract class TypeImpl implements DartType {
   String getDisplayString({
     @Deprecated('Only non-nullable by default mode is supported')
     bool withNullability = true,
+    bool preferTypeAlias = false,
   }) {
     var builder = ElementDisplayStringBuilder(
       // ignore:deprecated_member_use_from_same_package
       withNullability: withNullability,
+      preferTypeAlias: preferTypeAlias,
     );
     appendTo(builder);
     return builder.toString();

pkg/analyzer/test/src/diagnostics/invalid_assignment_test.dart

@@ -84,6 +84,48 @@ I x = E.v;
     ]);
   }
 
+  test_invalid_message_preferTypeAlias_functionType() async {
+    await assertErrorsInCode('''
+typedef A<T> = T Function();
+
+void f(A<int> a) {
+  A<String> b = a;
+}
+''', [
+      error(WarningCode.UNUSED_LOCAL_VARIABLE, 61, 1),
+      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 65, 1,
+          messageContains: ['A<int>', 'A<String>']),
+    ]);
+  }
+
+  test_invalid_message_preferTypeAlias_interfaceType() async {
+    await assertErrorsInCode('''
+typedef A<T> = List<T>;
+
+void f(A<int> a) {
+  A<String> b = a;
+}
+''', [
+      error(WarningCode.UNUSED_LOCAL_VARIABLE, 56, 1),
+      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 60, 1,
+          messageContains: ['A<int>', 'A<String>']),
+    ]);
+  }
+
+  test_invalid_message_preferTypeAlias_recordType() async {
+    await assertErrorsInCode('''
+typedef A<T> = (T, T);
+
+void f(A<int> a) {
+  A<String> b = a;
+}
+''', [
+      error(WarningCode.UNUSED_LOCAL_VARIABLE, 55, 1),
+      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 59, 1,
+          messageContains: ['A<int>', 'A<String>']),
+    ]);
+  }
+
   test_invalid_noCall_functionContext() async {
     await assertErrorsInCode('''
 class C {}