Simplify generated code for string interpolation by delaying the constant folding.

lib/compiler/implementation/ssa/codegen.dart

Index: lib/compiler/implementation/ssa/codegen.dart
diff --git a/lib/compiler/implementation/ssa/codegen.dart b/lib/compiler/implementation/ssa/codegen.dart
index e4437cf32676fd576ae0f599a32e9e656bff0308..d3bbb7906630c7ad76dc4dc31b8842cc8bc740db 100644
--- a/lib/compiler/implementation/ssa/codegen.dart
+++ b/lib/compiler/implementation/ssa/codegen.dart
@@ -1810,6 +1810,33 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
     endExpression(JSPrecedence.ASSIGNMENT_PRECEDENCE);
   }
 
+  void visitStringConcat(HStringConcat node) {
+    JSBinaryOperatorPrecedence operatorPrecedences = JSPrecedence.binary['+'];
+    beginExpression(operatorPrecedences.precedence);
+    useStringified(node.inputs[0], operatorPrecedences.left);
+    buffer.add(' + ');
+    // If the right hand side is a string concatenation itself it is
+    // safe to make it left associative.
+    JSPrecedence rightPrecedence = (node.inputs[1] is HStringConcat)

[Lasse Reichstein Nielsen, 2012/06/06 12:11:40]

JSPrecedence -> int.
The JSPrecedence class is just a static class container for the int-constants
(i.e., it's just a namespace).

[kasperl, 2012/06/06 13:31:03]

Done.

+        ? JSPrecedence.ADDITIVE_PRECEDENCE
+        : operatorPrecedences.right;
+    useStringified(node.inputs[1], rightPrecedence);
+    endExpression(operatorPrecedences.precedence);
+  }
+
+  void useStringified(HInstruction node, JSPrecedence precedence) {
+    if (node.isString()) {
+      use(node, precedence);
+    } else {
+      Element convertToString = compiler.findHelper(const SourceString("S"));
+      world.registerStaticUse(convertToString);
+      buffer.add(compiler.namer.isolateAccess(convertToString));

[Lasse Reichstein Nielsen, 2012/06/06 12:11:40]

Maybe we should have a function that does all this, so we can just write:
  addHelper(const SourceString("S"));

+      buffer.add('(');
+      use(node, JSPrecedence.EXPRESSION_PRECEDENCE);
+      buffer.add(')');
+    }
+  }
+
   void visitLiteralList(HLiteralList node) {
     generateArrayLiteral(node);
   }