Make string juxtaposition combine properly with string interpolations.

frog/tests/leg_only/src/LiteralStringJuxtapositionTest.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.
 
 main() {
   {
     // Generates identical compile time constants.
     var s1 = "abcdefgh";
     var s2 = "abcd" "efgh";
     var s3 = "ab" "cd" "ef" "gh";
@@ skipping 36 matching lines @@
   var ms2 = """abc
   def"""
   """
   ghi
   jkl
   """;
   Expect.isTrue("abc\n  def  ghi\n  jkl\n  " === ms2, "Multiline: $ms2");
 
   // Binds stronger than property access (it's considered one literal).
   Expect.equals(5, "ab" "cde".length, "Associativity");
+
+  // Check that interpolations are handled correctly.
+  {
+    var x = "foo";
+    var y = 42;
+    var z = true;
+    String e1 = "$x$y$z";
+    Expect.equals(e1, "$x" "$y$z");
+    Expect.equals(e1, "$x$y" "$z");
+    Expect.equals(e1, "$x" "$y" "$z");
+    String e2 = "-$x-$y-$z-";
+    Expect.equals(e2, "-" "$x" "-" "$y" "-" "$z" "-", "a");
+    Expect.equals(e2, "-$x" "-" "$y" "-" "$z" "-", "b");
+    Expect.equals(e2, "-" "$x-" "$y" "-" "$z" "-", "c");
+    Expect.equals(e2, "-" "$x" "-$y" "-" "$z" "-", "d");
+    Expect.equals(e2, "-" "$x" "-" "$y-" "$z" "-", "e");
+    Expect.equals(e2, "-" "$x" "-" "$y" "-$z" "-", "f");
+    Expect.equals(e2, "-" "$x" "-" "$y" "-" "$z-", "g");
+    Expect.equals(e2, "-" "$x-$y" "-" "$z" "-", "h");
+    Expect.equals(e2, "-" "$x-$y-$z" "-", "i");
+
+    Expect.equals("-$x-$y-", "-" "$x" "-" "$y" "-");
+    Expect.equals("-$x-$y", "-" "$x" "-" "$y");
+    Expect.equals("-$x$y-", "-" "$x" "$y" "-");
+    Expect.equals("$x-$y-", "$x" "-" "$y" "-");
+
+    Expect.equals("$x$y", "$x" "$y");
+    Expect.equals("$x$y", "$x" "" "$y");
+    Expect.equals("$x$y", "$x" "" "" "$y");
+    Expect.equals("$x-$y", "$x" "-" "$y");
+    Expect.equals("$x-$y", "$x" "-" "" "$y");
+    Expect.equals("$x-$y", "$x" "" "-" "$y");
+    Expect.equals("$x-$y", "$x" "" "-" "" "$y");
+    Expect.equals("$x--$y", "$x" "-" "-" "$y");
+    Expect.equals("$x--$y", "$x" "-" "-" "$y");
+    Expect.equals("$x--$y", "$x" "-" "-" "" "$y");
+    Expect.equals("$x--$y", "$x" "-" "" "-" "$y");
+    Expect.equals("$x--$y", "$x" "" "-" "-" "$y");
+
+    Expect.equals("$x-$y-$z", "${'$x' '-' '$y'}" "-" "$z");
+
+    Expect.equals(@"-foo-42-true-",
+                  @"-" "$x" @"""-""" """$y""" @'-' '$z' @'''-''', "j");
+    Expect.equals(@"-$x-42-true-",
+                  @"-" @"$x" @"""-""" """$y""" @'-' '$z' @'''-''', "j");
+    Expect.equals(@"-foo-$y-true-",
+                  @"-" "$x" @"""-""" @"""$y""" @'-' '$z' @'''-''', "j");
+    Expect.equals(@"-foo-42-$z-",
+                  @"-" "$x" @"""-""" """$y""" @'-' @'$z' @'''-''', "j");
+  }
 }