Extension types. Report CONFLICTING_GENERIC_INTERFACES.

Change-Id: Idd4a844ba5ee993b70c08aa9227e2f3a95fcc2f2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/319782
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>

pkg/analyzer/lib/src/error/codes.g.dart

@@ -521,13 +521,14 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
   );
 
   ///  Parameters:
-  ///  0: the name of the class implementing the conflicting interface
+  ///  0: the name of the kind of the element implementing the conflicting interface
-  ///  1: the first conflicting type
+  ///  1: the name of the element implementing the conflicting interface
-  ///  2: the second conflicting type
+  ///  2: the first conflicting type
+  ///  3: the second conflicting type
   static const CompileTimeErrorCode CONFLICTING_GENERIC_INTERFACES =
       CompileTimeErrorCode(
     'CONFLICTING_GENERIC_INTERFACES',
-    "The class '{0}' can't implement both '{1}' and '{2}' because the type "
+    "The {0} '{1}' can't implement both '{2}' and '{3}' because the type "
         "arguments are different.",
     hasPublishedDocs: true,
   );

pkg/analyzer/lib/src/generated/error_verifier.dart

@@ -707,6 +707,7 @@ class ErrorVerifier extends RecursiveAstVisitor<void>
 
       _duplicateDefinitionVerifier.checkExtensionType(node, declarationElement);
       _checkForConflictingClassMembers();
+      _checkForConflictingGenerics(node);
       _constructorFieldsVerifier.enterExtensionType(node, declarationElement);
       _checkForNonCovariantTypeParameterPositionInRepresentationType(
           node, element);
@@ -2175,6 +2176,7 @@ class ErrorVerifier extends RecursiveAstVisitor<void>
           CompileTimeErrorCode.CONFLICTING_GENERIC_INTERFACES,
           node.name,
           [
+            _enclosingClass!.kind.displayName,
             _enclosingClass!.name,
             error.first.getDisplayString(withNullability: true),
             error.second.getDisplayString(withNullability: true),

pkg/analyzer/messages.yaml

@@ -2079,13 +2079,14 @@ CompileTimeErrorCode:
       1: the name of the conflicting field
       2: the name of the class defining the method with which the field conflicts
   CONFLICTING_GENERIC_INTERFACES:
-    problemMessage: "The class '{0}' can't implement both '{1}' and '{2}' because the type arguments are different."
+    problemMessage: "The {0} '{1}' can't implement both '{2}' and '{3}' because the type arguments are different."
     hasPublishedDocs: true
     comment: |-
       Parameters:
-      0: the name of the class implementing the conflicting interface
+      0: the name of the kind of the element implementing the conflicting interface
-      1: the first conflicting type
+      1: the name of the element implementing the conflicting interface
-      2: the second conflicting type
+      2: the first conflicting type
+      3: the second conflicting type
     documentation: |-
       #### Description
 

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

@@ -205,6 +205,17 @@ enum E with M1, M2 {
     ]);
   }
 
+  test_extensionType() async {
+    await assertErrorsInCode('''
+class I<T> {}
+class A implements I<int> {}
+class B implements I<num> {}
+extension type C(Never it) implements A, B {}
+''', [
+      error(CompileTimeErrorCode.CONFLICTING_GENERIC_INTERFACES, 87, 1),
+    ]);
+  }
+
   test_mixin_on_implements() async {
     await assertErrorsInCode('''
 class I<T> {}