Fix for alphanumerics following braces.

BUG=3
[email protected], [email protected]

Review URL: https://chromiumcodereview.appspot.com//900093002

Author: pq

lib/src/rules/unnecessary_brace_in_string_interp.dart

@@ -6,31 +6,38 @@ library unnecessary_brace_in_string_interp;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/error.dart';
+import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/services/lint.dart';
 
-const msg = '''
-Interpolated simple identifiers (not followed by an alphanumeric string) do
-not need braces.
-''';
+final RegExp alphaNumeric = new RegExp(r'^[a-zA-Z0-9]');
+
+const msg =
+    '''Interpolated simple identifiers (not followed by an alphanumeric string) do
+not need braces.''';
 
 const name = 'UnnecessaryBraceInStringInterp';
 
+bool isAlphaNumeric(Token token) =>
+    token is StringToken && token.lexeme.startsWith(alphaNumeric);
+
 class UnnecessaryBraceInStringInterp extends Linter {
   @override
   AstVisitor getVisitor() => new Visitor(reporter);
 }
 
-class Visitor extends SimpleAstVisitor<Object> {
+class Visitor extends SimpleAstVisitor {
   ErrorReporter reporter;
   Visitor(this.reporter);
 
   @override
   visitStringInterpolation(StringInterpolation node) {
     var expressions = node.elements.where((e) => e is InterpolationExpression);
     for (InterpolationExpression expression in expressions) {
-      if (expression.expression is SimpleIdentifier &&
-          expression.rightBracket != null) {
-        reporter.reportErrorForNode(new LintCode(name, msg), expression, []);
+      if (expression.expression is SimpleIdentifier) {
+        Token bracket = expression.rightBracket;
+        if (bracket != null && !isAlphaNumeric(bracket.next)) {
+          reporter.reportErrorForNode(new LintCode(name, msg), expression, []);
+        }
       }
     }
   }

test/rules/unnecessary_brace_in_string_interp.dart

@@ -5,6 +5,9 @@
 main(args) {
   print('hello');
   print('hello $args');
+  print('hello $args!');
+  print('hello ${args}1');
   print('hello ${args}'); //LINT
+  print('hello ${args}!'); //LINT
   print('hello ${args.length}');
 }