Fix constant evaluation logic for String.length.

pkg/analyzer/test/generated/all_the_rest_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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.all_the_rest_test;
 
 import 'dart:collection';
@@ skipping 2059 matching lines @@
     expect(ConstantValueComputer.isValidPublicSymbol("if"), isFalse);
     expect(ConstantValueComputer.isValidPublicSymbol("if.foo"), isFalse);
     expect(ConstantValueComputer.isValidPublicSymbol("foo.if"), isFalse);
     expect(ConstantValueComputer.isValidPublicSymbol("foo=.bar"), isFalse);
     expect(ConstantValueComputer.isValidPublicSymbol("foo."), isFalse);
     expect(ConstantValueComputer.isValidPublicSymbol("+.foo"), isFalse);
     expect(ConstantValueComputer.isValidPublicSymbol("void.foo"), isFalse);
     expect(ConstantValueComputer.isValidPublicSymbol("foo.void"), isFalse);
   }
 
+  void test_length_of_improperly_typed_string_expression() {
+    // Since type annotations are ignored in unchecked mode, the improper
+    // types on s1 and s2 shouldn't prevent us from evaluating i to
+    // 'alpha'.length.
+    CompilationUnit compilationUnit = resolveSource('''
+const int s1 = 'alpha';
+const int s2 = 'beta';
+const int i = (true ? s1 : s2).length;
+''');
+    ConstTopLevelVariableElementImpl element =
+        findTopLevelDeclaration(compilationUnit, 'i').element;
+    EvaluationResultImpl result = element.evaluationResult;
+    expect(_assertValidInt(result), 5);
+  }
+
+  void test_length_of_improperly_typed_string_identifier() {
+    // Since type annotations are ignored in unchecked mode, the improper type
+    // on s shouldn't prevent us from evaluating i to 'alpha'.length.
+    CompilationUnit compilationUnit = resolveSource('''
+const int s = 'alpha';
+const int i = s.length;
+''');
+    ConstTopLevelVariableElementImpl element =
+        findTopLevelDeclaration(compilationUnit, 'i').element;
+    EvaluationResultImpl result = element.evaluationResult;
+    expect(_assertValidInt(result), 5);
+  }
+
   void test_symbolLiteral_void() {
     CompilationUnit compilationUnit =
         resolveSource("const voidSymbol = #void;");
     VariableDeclaration voidSymbol =
         findTopLevelDeclaration(compilationUnit, "voidSymbol");
     EvaluationResultImpl voidSymbolResult =
         (voidSymbol.element as VariableElementImpl).evaluationResult;
     DartObjectImpl value = voidSymbolResult.value;
     expect(value.type, typeProvider.symbolType);
     expect(value.value, "void");
@@ skipping 6694 matching lines @@
     if (_expectedExternalScriptName == null) {
       expect(scriptSource, isNull, reason: "script $scriptIndex");
     } else {
       expect(scriptSource, isNotNull, reason: "script $scriptIndex");
       String actualExternalScriptName = scriptSource.shortName;
       expect(actualExternalScriptName, _expectedExternalScriptName,
           reason: "script $scriptIndex");
     }
   }
 }