Reapply "Enable full type-checks in checked mode."

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

Index: sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart b/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
index 2d9c62a1dd6c88c157346b9aa3617fa855d71c14..09df7c19cc9550e28a097d8b4d37b6a94b5ba67e 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
@@ -606,7 +606,9 @@ class SsaConstantFolder extends HBaseVisitor implements OptimizationPhase {
   HInstruction visitTypeConversion(HTypeConversion node) {
     HInstruction value = node.inputs[0];
     DartType type = node.typeExpression;
-    if (type != null && !type.isRaw) return node;
+    if (type != null && (!type.isRaw || type.kind == TypeKind.TYPE_VARIABLE)) {
+      return node;
+    }
     HType convertedType = node.instructionType;
     if (convertedType.isUnknown()) return node;
     HType combinedType = value.instructionType.intersection(
@@ -723,9 +725,15 @@ class SsaConstantFolder extends HBaseVisitor implements OptimizationPhase {
     // interceptor.
     HInstruction value = node.inputs.last;
     if (compiler.enableTypeAssertions) {
+      DartType type = field.computeType(compiler);
+      if (!type.isRaw || type.kind == TypeKind.TYPE_VARIABLE) {
+        // We cannot generate the correct type representation here, so don't
+        // inline this access.
+        return node;
+      }
       HInstruction other = value.convertType(
           compiler,
-          field.computeType(compiler),
+          type,
           HTypeConversion.CHECKED_MODE_CHECK);
       if (other != value) {
         node.block.addBefore(node, other);