Remove uses of string + from API document generator.

lib/dartdoc/frog/world.dart

 // Copyright (c) 2012, 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.
 
 /** The one true [World]. */
 World world;
 
 /**
  * Experimental phase to enable await, only set when using the
  * await/awaitc.dart entrypoint.
@@ skipping 266 matching lines @@
       _topNames[name] = named;
       return;
     }
     if (existing === named) {
       // This happens for a simple non-hidden native class where the native name
       // is the same as the default jsname, e.g. class A native 'A' {}.
       return;
     }
 
     info('mangling matching top level name "${named.jsname}" in '
-         + 'both "${named.library.jsname}" and "${existing.library.jsname}"');
+         'both "${named.library.jsname}" and "${existing.library.jsname}"');
 
     // resolve conflicts based on priority
     int existingPri = existing.jsnamePriority;
     int namedPri = named.jsnamePriority;
     if (existingPri > namedPri || namedPri == 0) {
       // Either existing was higher priority, or they're both 0 so first one
       // wins.
       _renameJavascriptTopName(named);
     } else if (namedPri > existingPri) {
       // New one takes priority over existing
       _renameJavascriptTopName(existing);
     } else {
       if (named.isNative) {
         final msg = 'conflicting JS name "$name" of same '
-            + 'priority $existingPri: (already defined in) '
-            + '${existing.span.locationText} with priority $namedPri)';
+            'priority $existingPri: (already defined in) '
+            '${existing.span.locationText} with priority $namedPri)';
         // We trust that conflicting native names in builtin libraries
         // are harmless. Most cases there are no conflicts, currently
         // isolates in coreimpl and dart:dom_deprecated both define
         // web workers to avoid adding a dependency from corelib to
         // dart:dom_deprecated.
         world.info(msg, named.span, existing.span);
       } else {
         // Conflicting js name in same library. This happens because
         // of two different type arguments with the same name but in
         // different libraries.
         _renameJavascriptTopName(existing);
       }
     }
   }
 
   /** Renames an [Element] that had a name conflict in the generated JS. */
   _renameJavascriptTopName(Element named) {
     named._jsname = '${named.library.jsname}_${named.jsname}';
     final existing = _topNames[named.jsname];
     if (existing != null && existing != named) {
       // If this happens it means the library name wasn't unique enough.
       world.internalError('name mangling failed for "${named.jsname}" '
-          + '("${named.jsname}" defined also in ${existing.span.locationText})',
+          '("${named.jsname}" defined also in ${existing.span.locationText})',
           named.span);
     }
     _topNames[named.jsname] = named;
   }
 
   _addType(Type type) {
     // Top types don't have a name - we will capture their members in
     // [_addMember].
     if (!type.isTop) _addTopName(type);
   }
@@ skipping 10 matching lines @@
       _jsKeywords = new Set.from([
         'break', 'case', 'catch', 'continue', 'debugger', 'default',
         'delete', 'do', 'else', 'finally', 'for', 'function', 'if',
         'in', 'instanceof', 'new', 'return', 'switch', 'this', 'throw',
         'try', 'typeof', 'var', 'void', 'while', 'with',
         'class', 'enum', 'export', 'extends', 'import', 'super',
         'implements', 'interface', 'let', 'package', 'private',
         'protected', 'public', 'static', 'yield', 'native']);
     }
     if (_jsKeywords.contains(name)) {
-      return name + '_';
+      return '${name}_';
     } else {
       // regexs for better perf?
       return name.replaceAll(@'$', @'$$').replaceAll(':', @'$');
     }
   }
 
   /**
    * Runs the compiler and updates the output file. The output will either be
    * the program, or a file that throws an error when run.
    */
@@ skipping 232 matching lines @@
       // TODO(jimhug): Multiple spans cleaner...
       messageHandler(prefix, message, span);
       if (span1 != null) {
         messageHandler(prefix, message, span1);
       }
       if (span2 != null) {
         messageHandler(prefix, message, span2);
       }
     } else {
       final messageWithPrefix = options.useColors
-          ? (color + prefix + _NO_COLOR + message) : (prefix + message);
+          ? ('$color$prefix${_NO_COLOR}$message') : ('$prefix$message');
 
       var text = messageWithPrefix;
       if (span != null) {
         text = span.toMessageString(messageWithPrefix);
       }
       print(text);
       if (span1 != null) {
         print(span1.toMessageString(messageWithPrefix));
       }
       if (span2 != null) {
         print(span2.toMessageString(messageWithPrefix));
       }
     }
 
     if (throwing) {
-      throw new CompilerException(prefix + message, span);
+      throw new CompilerException('$prefix$message', span);
     }
   }
 
   /** [message] is considered a static compile-time error by the Dart lang. */
   void error(String message,
       [SourceSpan span, SourceSpan span1, SourceSpan span2]) {
     errors++;
     _message(_RED_COLOR, 'error: ', message,
         span, span1, span2, options.throwOnErrors);
   }
@@ skipping 69 matching lines @@
 
   withTiming(String name, f()) {
     final sw = new Stopwatch();
     sw.start();
     var result = f();
     sw.stop();
     info('$name in ${sw.elapsedInMs()}msec');
     return result;
   }
 }