VM: [KERNEL] handle single-argument string interpolation in VM

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

 // Copyright (c) 2016, 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 fasta.body_builder;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
 
 import '../parser/error_kind.dart' show ErrorKind;
 
@@ skipping 800 matching lines @@
     debugEvent("endLiteralString");
     if (interpolationCount == 0) {
       Token token = pop();
       push(new StringLiteral(unescapeString(token.lexeme)));
     } else {
       List parts = popList(1 + interpolationCount * 2);
       Token first = parts.first;
       Token last = parts.last;
       Quote quote = analyzeQuote(first.lexeme);
       List<Expression> expressions = <Expression>[];
-      expressions
+      // Contains more then just \' or \".

[ahe, 2017/03/14 14:58:44]

than.

+      if (first.lexeme.length > 1) {
+        expressions
           .add(new StringLiteral(unescapeFirstStringPart(first.lexeme, quote)));
+      }
       for (int i = 1; i < parts.length - 1; i++) {
         var part = parts[i];
         if (part is Token) {
-          expressions.add(new StringLiteral(unescape(part.lexeme, quote)));
+          if (part.lexeme.length != 0) {
+            expressions.add(new StringLiteral(unescape(part.lexeme, quote)));
+          }
         } else {
           expressions.add(toValue(part));
         }
       }
-      expressions
+      // Contains more then just \' or \".

[ahe, 2017/03/14 14:58:44]

Than.

+      if (last.lexeme.length > 1) {
+        expressions
           .add(new StringLiteral(unescapeLastStringPart(last.lexeme, quote)));
+      }
       push(new StringConcatenation(expressions)
         ..fileOffset = endToken.charOffset);
     }
   }
 
   @override
   void handleScript(Token token) {
     debugEvent("Script");
   }
 
@@ skipping 1926 matching lines @@
   } else if (node is PrefixBuilder) {
     return node.name;
   } else if (node is ThisAccessor) {
     return node.isSuper ? "super" : "this";
   } else if (node is BuilderAccessor) {
     return node.plainNameForRead;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }