Revert "Separate HTypeConversion checked type from output type."

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

Index: sdk/lib/_internal/compiler/implementation/ssa/types_propagation.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ssa/types_propagation.dart b/sdk/lib/_internal/compiler/implementation/ssa/types_propagation.dart
index 600d7a97249db5add8abf76ea85ab7bb0f74b1ad..e3a107b5abc90afdae0ffa1329418bcfa668b437 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/types_propagation.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/types_propagation.dart
@@ -140,21 +140,21 @@ class SsaTypePropagator extends HBaseVisitor implements OptimizationPhase {
   }
 
   HType visitTypeConversion(HTypeConversion instruction) {
-    HType inputType = instruction.checkedInput.instructionType;
-    HType checkedType = instruction.checkedType;
-    if (instruction.isArgumentTypeCheck || instruction.isReceiverTypeCheck) {
-      // We must make sure a type conversion for receiver or argument check
-      // does not try to do an int check, because an int check is not enough.
-      // We only do an int check if the input is integer or null.
-      if (checkedType.isNumber()
-          && !checkedType.isDouble()
-          && inputType.isIntegerOrNull()) {
-        instruction.checkedType = HType.INTEGER;
-      } else if (checkedType.isInteger() && !inputType.isIntegerOrNull()) {
-        instruction.checkedType = HType.NUMBER;
-      }
+    HType oldType = instruction.instructionType;
+    // Do not change a checked mode check.
+    if (instruction.isCheckedModeCheck) return oldType;
+    // We must make sure a type conversion for receiver or argument check
+    // does not try to do an int check, because an int check is not enough.
+    // We only do an int check if the input is integer or null.
+    HInstruction checked = instruction.checkedInput;
+    if (oldType.isNumber()
+        && !oldType.isDouble()
+        && checked.isIntegerOrNull()) {
+      return HType.INTEGER;
+    } else if (oldType.isInteger() && !checked.isIntegerOrNull()) {
+      return HType.NUMBER;
     }
-    return checkedType.intersection(inputType, compiler);
+    return oldType;
   }
 
   HType visitTypeKnown(HTypeKnown instruction) {