Fix for alphanumerics following braces.

lib/src/rules/unnecessary_brace_in_string_interp.dart

Index: lib/src/rules/unnecessary_brace_in_string_interp.dart
diff --git a/lib/src/rules/unnecessary_brace_in_string_interp.dart b/lib/src/rules/unnecessary_brace_in_string_interp.dart
index fa8e9ee9a86a4b6abc197a6953e852e741519355..13ef1d651637c1003764c44cd43eb537ff6436f3 100644
--- a/lib/src/rules/unnecessary_brace_in_string_interp.dart
+++ b/lib/src/rules/unnecessary_brace_in_string_interp.dart
@@ -6,8 +6,11 @@ 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';
 
+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.

[Brian Wilkerson, 2015/02/05 01:38:42]

Don't include end-of-line characters in the message. Clients are responsible for
wrapping messages where necessary.

[pquitslund, 2015/02/05 03:42:06]

Done.

@@ -15,6 +18,9 @@ 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);
@@ -28,9 +34,11 @@ class Visitor extends SimpleAstVisitor<Object> {
   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, []);

[Brian Wilkerson, 2015/02/05 01:38:42]

I would recommend defining static constant fields in LintCode. I think it makes
it easier to find where messages are being produced when all you're given in a
bug report is the message that was displayed.

[pquitslund, 2015/02/05 03:42:06]

Agreed!  That said, if I understand you right, I'm not completely sure how that
would work since LintCode is defined in the analyzer package and the lints are
contributed outside it...

+        }
       }
     }
   }