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

lib/compiler/implementation/ssa/nodes.dart

Index: lib/compiler/implementation/ssa/nodes.dart
diff --git a/lib/compiler/implementation/ssa/nodes.dart b/lib/compiler/implementation/ssa/nodes.dart
index b84ddb4dcd280e92c5810067b2ffa8633000041c..8fa7e885db7893922c3dda37dd4419ba8759171a 100644
--- a/lib/compiler/implementation/ssa/nodes.dart
+++ b/lib/compiler/implementation/ssa/nodes.dart
@@ -51,6 +51,7 @@ interface HVisitor<R> {
   R visitShiftRight(HShiftRight node);
   R visitStatic(HStatic node);
   R visitStaticStore(HStaticStore node);
+  R visitStringConcat(HStringConcat node);
   R visitSubtract(HSubtract node);
   R visitThis(HThis node);
   R visitThrow(HThrow node);
@@ -301,6 +302,7 @@ class HBaseVisitor extends HGraphVisitor implements HVisitor {
   visitSubtract(HSubtract node) => visitBinaryArithmetic(node);
   visitStatic(HStatic node) => visitInstruction(node);
   visitStaticStore(HStaticStore node) => visitInstruction(node);
+  visitStringConcat(HStringConcat node) => visitInstruction(node);
   visitThis(HThis node) => visitParameterValue(node);
   visitThrow(HThrow node) => visitControlFlow(node);
   visitTry(HTry node) => visitControlFlow(node);
@@ -2205,6 +2207,14 @@ class HTypeConversion extends HCheck {
   bool hasSideEffects() => checked;
 }
 
+class HStringConcat extends HInstruction {
+  HStringConcat(inputs) : super(inputs);
+  HType get guaranteedType() => HType.STRING;
+
+  accept(HVisitor visitor) => visitor.visitStringConcat(this);
+  toString() => "string concat";

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

Should this class be allowed to have more than two inputs? Nothing seems to
prevent it, the optimize code handles it, but codegen doesn't.

If you don't expect to allow 3+ inputs later, consider adding left/right getters
to extract the inputs. Or just extend HInvokeBinary, if possible. Otherwise make
a comment about it.

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

Changed the constructor to take exactly two arguments (left and right).

+}
+
 /** Non-block-based (aka. traditional) loop information. */
 class HLoopInformation {
   final HBasicBlock header;