[Type checker] Pull the null check into swift::isSIMDOperator().

(cherry picked from commit 052d4c1)

Author: DougGregor

lib/Sema/CSStep.cpp

@@ -491,6 +491,9 @@ bool DisjunctionStep::shouldStopAt(const DisjunctionChoice &choice) const {
 }
 
 bool swift::isSIMDOperator(ValueDecl *value) {
+  if (!value)
+    return false;
+
   auto func = dyn_cast<FuncDecl>(value);
   if (!func)
     return false;
@@ -556,10 +559,8 @@ bool DisjunctionStep::shortCircuitDisjunctionAt(
   // If we have an operator from the SIMDOperators module, and the prior
   // choice was not from the SIMDOperators module, we're done.
   if (currentChoice->getKind() == ConstraintKind::BindOverload &&
-      currentChoice->getOverloadChoice().isDecl() &&
       isSIMDOperator(currentChoice->getOverloadChoice().getDecl()) &&
       lastSuccessfulChoice->getKind() == ConstraintKind::BindOverload &&
-      lastSuccessfulChoice->getOverloadChoice().isDecl() &&
       !isSIMDOperator(lastSuccessfulChoice->getOverloadChoice().getDecl()) &&
       !ctx.LangOpts.SolverEnableOperatorDesignatedTypes) {
     return true;

lib/Sema/ConstraintSystem.cpp

@@ -1459,7 +1459,7 @@ static ArrayRef<OverloadChoice> partitionSIMDOperators(
   // Check whether we have any SIMD operators.
   bool foundSIMDOperator = false;
   for (const auto &choice : choices) {
-    if (choice.isDecl() && isSIMDOperator(choice.getDecl())) {
+    if (isSIMDOperator(choice.getDecl())) {
       foundSIMDOperator = true;
       break;
     }
@@ -1471,8 +1471,7 @@ static ArrayRef<OverloadChoice> partitionSIMDOperators(
   scratch.assign(choices.begin(), choices.end());
   std::stable_partition(scratch.begin(), scratch.end(),
                         [](const OverloadChoice &choice) {
-                          return !choice.isDecl() ||
-                                 !isSIMDOperator(choice.getDecl());
+                          return !isSIMDOperator(choice.getDecl());
                         });
 
   return scratch;