Analyzer: Do not report const constructors with mixed in synthetic fields

Fixes #37810

Also report the offending fields in the error.

Change-Id: I8328bf5f16f56f1b70bbe4bdb7623ade6f11943c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/151027
Commit-Queue: Samuel Rawlins <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: srawlins

pkg/analyzer/lib/error/error.dart

@@ -100,6 +100,7 @@ const List<ErrorCode> errorCodeValues = [
   CompileTimeErrorCode.CONST_CONSTRUCTOR_THROWS_EXCEPTION,
   CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_FIELD_INITIALIZED_BY_NON_CONST,
   CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD,
+  CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELDS,
   CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_CONST_SUPER,
   CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_FINAL_FIELD,
   CompileTimeErrorCode.CONST_DEFERRED_CLASS,

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

@@ -960,15 +960,43 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
    * implicitly declared constructor named ... is declared. If Sq is a
    * generative const constructor, and M does not declare any fields, Cq is
    * also a const constructor.
+   *
+   * Parameters:
+   * 0: the name of the instance field.
    */
   static const CompileTimeErrorCode CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD =
-      CompileTimeErrorCode(
+      CompileTimeErrorCodeWithUniqueName(
+          'CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD',
+          'CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD',
+          "This constructor can't be declared 'const' because a mixin adds the "
+              "instance field: {0}.",
+          correction: "Try removing the 'const' keyword or removing the 'with' "
+              "clause from the class declaration, or removing the field from "
+              "the mixin class.");
+
+  /**
+   * 7.6.3 Constant Constructors: The superinitializer that appears, explicitly
+   * or implicitly, in the initializer list of a constant constructor must
+   * specify a constant constructor of the superclass of the immediately
+   * enclosing class or a compile-time error occurs.
+   *
+   * 12.1 Mixin Application: For each generative constructor named ... an
+   * implicitly declared constructor named ... is declared. If Sq is a
+   * generative const constructor, and M does not declare any fields, Cq is
+   * also a const constructor.
+   *
+   * Parameters:
+   * 0: the names of the instance fields.
+   */
+  static const CompileTimeErrorCode CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELDS =
+      CompileTimeErrorCodeWithUniqueName(
           'CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD',
-          "Const constructor can't be declared for a class with a mixin "
-              "that declares an instance field.",
-          correction: "Try removing the 'const' keyword or "
-              "removing the 'with' clause from the class declaration, "
-              "or removing fields from the mixin class.");
+          'CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELDS',
+          "This constructor can't be declared 'const' because the mixins add "
+              "the instance fields: {0}.",
+          correction: "Try removing the 'const' keyword or removing the 'with' "
+              "clause from the class declaration, or removing the fields from "
+              "the mixin classes.");
 
   /**
    * 7.6.3 Constant Constructors: The superinitializer that appears, explicitly

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

@@ -1903,12 +1903,12 @@ class ErrorVerifier extends RecursiveAstVisitor<void> {
     }
   }
 
-  /**
-   * Verify that if the given [constructor] declaration is 'const' then there
-   * are no invocations of non-'const' super constructors.
-   *
-   * See [CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_CONST_SUPER].
-   */
+  /// Verify that if the given [constructor] declaration is 'const' then there
+  /// are no invocations of non-'const' super constructors, and that there are
+  /// no instance variables mixed in.
+  ///
+  /// See [CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_CONST_SUPER], and
+  /// [CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD].
   void _checkForConstConstructorWithNonConstSuper(
       ConstructorDeclaration constructor) {
     if (!_enclosingExecutable.isConstConstructor) {
@@ -1920,21 +1920,26 @@ class ErrorVerifier extends RecursiveAstVisitor<void> {
     }
 
     // check for mixins
-    var hasInstanceField = false;
+    var instanceFields = <FieldElement>[];
     for (var mixin in _enclosingClass.mixins) {
-      var fields = mixin.element.fields;
-      for (var i = 0; i < fields.length; ++i) {
-        if (!fields[i].isStatic) {
-          hasInstanceField = true;
-          break;
-        }
-      }
+      instanceFields.addAll(mixin.element.fields
+          .where((field) => !field.isStatic && !field.isSynthetic));
     }
-    if (hasInstanceField) {
-      // TODO(scheglov) Provide the list of fields.
+    if (instanceFields.length == 1) {
+      var field = instanceFields.single;
       _errorReporter.reportErrorForNode(
           CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD,
-          constructor.returnType);
+          constructor.returnType,
+          ["'${field.enclosingElement.name}.${field.name}'"]);
+      return;
+    } else if (instanceFields.length > 1) {
+      var fieldNames = instanceFields
+          .map((field) => "'${field.enclosingElement.name}.${field.name}'")
+          .join(', ');
+      _errorReporter.reportErrorForNode(
+          CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELDS,
+          constructor.returnType,
+          [fieldNames]);
       return;
     }
 

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

@@ -15,7 +15,46 @@ main() {
 
 @reflectiveTest
 class ConstConstructorWithMixinWithFieldTest extends DriverResolutionTest {
-  test_class_instance() async {
+  test_class_instance_final() async {
+    await assertErrorsInCode('''
+class A {
+  final a = 0;
+}
+
+class B extends Object with A {
+  const B();
+}
+''', [
+      error(
+          CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD, 68, 1),
+    ]);
+  }
+
+  test_class_instance_getter() async {
+    await assertNoErrorsInCode('''
+class A {
+  int get a => 7;
+}
+
+class B extends Object with A {
+  const B();
+}
+''');
+  }
+
+  test_class_instance_setter() async {
+    await assertNoErrorsInCode('''
+class A {
+  set a(int x) {}
+}
+
+class B extends Object with A {
+  const B();
+}
+''');
+  }
+
+  test_class_instanceField() async {
     await assertErrorsInCode('''
 class A {
   var a;
@@ -31,18 +70,20 @@ class B extends Object with A {
     ]);
   }
 
-  test_class_instance_final() async {
+  test_class_multipleInstanceFields() async {
     await assertErrorsInCode('''
 class A {
-  final a = 0;
+  var a;
+  var b;
 }
 
 class B extends Object with A {
   const B();
 }
 ''', [
+      error(CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_FINAL_FIELD, 71, 1),
       error(
-          CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD, 68, 1),
+          CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELDS, 71, 1),
     ]);
   }