Report a compile-time error if a const field is multiply initialized.

pkg/analyzer/test/generated/compile_time_error_code_test.dart

 // Copyright (c) 2014, 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.
 
 library engine.compile_time_error_code_test;
 
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
 import 'package:analyzer/src/generated/source_io.dart';
@@ skipping 1022 matching lines @@
     _check_constEvalThrowsException_binary_null("5 + null", true);
   }
 
   void test_constEvalThrowsException_divisionByZero() {
     Source source = addSource("const C = 1 ~/ 0;");
     computeLibrarySourceErrors(source);
     assertErrors(source, [CompileTimeErrorCode.CONST_EVAL_THROWS_IDBZE]);
     verify([source]);
   }
 
+  void test_constEvalThrowsException_finalAlreadySet_initializer() {
+    // If a final variable has an initializer at the site of its declaration,
+    // and at the site of the constructor, then invoking that constructor would
+    // produce a runtime error; hence invoking that constructor via the "const"
+    // keyword results in a compile-time error.
+    Source source = addSource('''
+class C {
+  final x = 1;
+  const C() : x = 2;
+}
+var x = const C();
+''');
+    computeLibrarySourceErrors(source);
+    assertErrors(source, [
+      CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION,
+      StaticWarningCode.FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION
+    ]);
+    verify([source]);
+  }
+
+  void test_constEvalThrowsException_finalAlreadySet_initializing_formal() {
+    // If a final variable has an initializer at the site of its declaration,
+    // and it is initialized using an initializing formal at the site of the
+    // constructor, then invoking that constructor would produce a runtime
+    // error; hence invoking that constructor via the "const" keyword results
+    // in a compile-time error.
+    Source source = addSource('''
+class C {
+  final x = 1;
+  const C(this.x);
+}
+var x = const C(2);
+''');
+    computeLibrarySourceErrors(source);
+    assertErrors(source, [
+      CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION,
+      StaticWarningCode.FINAL_INITIALIZED_IN_DECLARATION_AND_CONSTRUCTOR
+    ]);
+    verify([source]);
+  }
+
   void test_constEvalThrowsException_unaryBitNot_null() {
     Source source = addSource("const C = ~null;");
     computeLibrarySourceErrors(source);
     assertErrors(source, [CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION]);
     // no verify(), '~null' is not resolved
   }
 
   void test_constEvalThrowsException_unaryNegated_null() {
     Source source = addSource("const C = -null;");
     computeLibrarySourceErrors(source);
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         source, [CompileTimeErrorCode.WRONG_NUMBER_OF_PARAMETERS_FOR_OPERATOR]);
     verify([source]);
     reset();
   }
 
   void _check_wrongNumberOfParametersForOperator1(String name) {
     _check_wrongNumberOfParametersForOperator(name, "");
     _check_wrongNumberOfParametersForOperator(name, "a, b");
   }
 }