Rip-off the backend type inferrer.

sdk/lib/_internal/compiler/implementation/ssa/builder.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/builder.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/ssa/builder.dart	(revision 23797)
+++ sdk/lib/_internal/compiler/implementation/ssa/builder.dart	(working copy)
@@ -54,33 +54,11 @@
       if (!identical(kind, ElementKind.FIELD)) {
         FunctionElement function = element;
         graph.calledInLoop = compiler.world.isCalledInLoop(function);
-        OptionalParameterTypes defaultValueTypes = null;
         FunctionSignature signature = function.computeSignature(compiler);
-        if (signature.optionalParameterCount > 0) {
-          defaultValueTypes =
-              new OptionalParameterTypes(signature.optionalParameterCount);
-          int index = 0;
-          signature.forEachOptionalParameter((Element parameter) {
-            Constant defaultValue = builder.compileVariable(parameter);
-            HType type = HGraph.mapConstantTypeToSsaType(defaultValue);
-            defaultValueTypes.update(index, parameter.name, type);
-            index++;
-          });
-        } else {
-          // BUG(10938): the types are stored in the wrong order.
-          // order.
-          HTypeList parameterTypes =
-              backend.optimisticParameterTypes(element.declaration,
-                                               defaultValueTypes);
-          if (!parameterTypes.allUnknown) {
-            int i = 0;
-            signature.forEachParameter((Element param) {
-              builder.parameters[param].instructionType = parameterTypes[i++];
-            });
-          }
-          backend.registerParameterTypesOptimization(
-              element.declaration, parameterTypes, defaultValueTypes);
-        }
+        signature.forEachOptionalParameter((Element parameter) {
+          // This ensures the default value will be computed.
+          builder.compileVariable(parameter);
+        });
       }
 
       if (compiler.tracer.enabled) {
@@ -1141,12 +1119,6 @@
     List<HInstruction> compiledArguments;
     bool isInstanceMember = function.isInstanceMember();
 
-    if (function.isGenerativeConstructor()) {
-      // The optimistic field type optimization requires
-      // to know all generative constructors seen in codegen.
-      backend.registerConstructor(function);
-    }
-
     if (currentNode == null
         || currentNode.asForIn() != null
         || !isInstanceMember
@@ -3790,14 +3762,6 @@
 
     if (type == null) {
       type = new HType.inferredReturnTypeForElement(element, compiler);
-      if (type.isUnknown()) {
-        // TODO(ngeoffray): Only do this if knowing the return type is
-        // useful.
-        type =
-            builder.backend.optimisticReturnTypesWithRecompilationOnTypeChange(
-                currentElement, element);
-        if (type == null) type = HType.UNKNOWN;
-      }
     }
     // TODO(5346): Try to avoid the need for calling [declaration] before
     // creating an [HInvokeStatic].