[Sema] Add getDeclOrNull to OverloadChoice

This helps clean up a bunch of call sites.

(cherry picked from commit 8aa7401)

Author: hamishknight

lib/Sema/CSApply.cpp

@@ -4591,8 +4591,7 @@ namespace {
     buildKeyPathPropertyComponent(const SelectedOverload &overload,
                                   SourceLoc componentLoc,
                                   ConstraintLocator *locator) {
-      if (overload.choice.isDecl()) {
-        auto property = overload.choice.getDecl();
+      if (auto *property = overload.choice.getDeclOrNull()) {
         // Key paths can only refer to properties currently.
         auto varDecl = cast<VarDecl>(property);
         // Key paths don't work with mutating-get properties.
@@ -4909,10 +4908,8 @@ static ConcreteDeclRef resolveLocatorToDecl(
     // Overloaded and unresolved cases: find the resolved overload.
     auto anchorLocator = cs.getConstraintLocator(anchor);
     if (auto selected = findOvlChoice(anchorLocator)) {
-      if (selected->choice.isDecl())
-        return getConcreteDeclRef(selected->choice.getDecl(),
-                                  selected->openedType,
-                                  anchorLocator);
+      if (auto *decl = selected->choice.getDeclOrNull())
+        return getConcreteDeclRef(decl, selected->openedType, anchorLocator);
     }
   }
 
@@ -4921,10 +4918,8 @@ static ConcreteDeclRef resolveLocatorToDecl(
     auto anchorLocator = cs.getConstraintLocator(anchor,
                            ConstraintLocator::UnresolvedMember);
     if (auto selected = findOvlChoice(anchorLocator)) {
-      if (selected->choice.isDecl())
-        return getConcreteDeclRef(selected->choice.getDecl(),
-                                  selected->openedType,
-                                  anchorLocator);
+      if (auto *decl = selected->choice.getDeclOrNull())
+        return getConcreteDeclRef(decl, selected->openedType, anchorLocator);
     }
   }
 
@@ -4933,10 +4928,8 @@ static ConcreteDeclRef resolveLocatorToDecl(
     auto anchorLocator = cs.getConstraintLocator(anchor,
                                                  ConstraintLocator::Member);
     if (auto selected = findOvlChoice(anchorLocator)) {
-      if (selected->choice.isDecl())
-        return getConcreteDeclRef(selected->choice.getDecl(),
-                                  selected->openedType,
-                                  anchorLocator);
+      if (auto *decl = selected->choice.getDeclOrNull())
+        return getConcreteDeclRef(decl, selected->openedType, anchorLocator);
     }
   }
 
@@ -4949,10 +4942,8 @@ static ConcreteDeclRef resolveLocatorToDecl(
     auto anchorLocator =
       cs.getConstraintLocator(anchor, ConstraintLocator::SubscriptMember);
     if (auto selected = findOvlChoice(anchorLocator)) {
-      if (selected->choice.isDecl())
-        return getConcreteDeclRef(selected->choice.getDecl(),
-                                  selected->openedType,
-                                  anchorLocator);
+      if (auto *decl = selected->choice.getDeclOrNull())
+        return getConcreteDeclRef(decl, selected->openedType, anchorLocator);
     }
   }
 

lib/Sema/CSDiag.cpp

@@ -940,9 +940,8 @@ bool FailureDiagnosis::diagnoseGeneralOverloadFailure(Constraint *constraint) {
   if (constraint->getKind() == ConstraintKind::Disjunction) {
     for (auto elt : constraint->getNestedConstraints()) {
       if (elt->getKind() != ConstraintKind::BindOverload) continue;
-      if (!elt->getOverloadChoice().isDecl()) continue;
-      auto candidate = elt->getOverloadChoice().getDecl();
-      diagnose(candidate, diag::found_candidate);
+      if (auto *candidate = elt->getOverloadChoice().getDeclOrNull())
+        diagnose(candidate, diag::found_candidate);
     }
   }
 

lib/Sema/CSGen.cpp

@@ -602,9 +602,9 @@ namespace {
     unsigned numFavoredConstraints = 0;
     Constraint *firstFavored = nullptr;
     for (auto constraint : disjunction->getNestedConstraints()) {
-      if (!constraint->getOverloadChoice().isDecl())
+      auto *decl = constraint->getOverloadChoice().getDeclOrNull();
+      if (!decl)
         continue;
-      auto decl = constraint->getOverloadChoice().getDecl();
 
       if (mustConsider && mustConsider(decl)) {
         // Roll back any constraints we favored.

lib/Sema/CSSimplify.cpp

@@ -828,8 +828,7 @@ getCalleeDeclAndArgs(ConstraintSystem &cs,
                            hasTrailingClosure, nullptr);
 
   // If there's a declaration, return it.
-  if (choice->isDecl()) {
-    auto decl = choice->getDecl();
+  if (auto *decl = choice->getDeclOrNull()) {
     bool hasCurriedSelf = false;
     if (decl->getDeclContext()->isTypeContext()) {
       if (auto function = dyn_cast<AbstractFunctionDecl>(decl)) {
@@ -4570,9 +4569,7 @@ fixMemberRef(ConstraintSystem &cs, Type baseTy,
              Optional<MemberLookupResult::UnviableReason> reason = None) {
   // Not all of the choices handled here are going
   // to refer to a declaration.
-  if (choice.isDecl()) {
-    auto *decl = choice.getDecl();
-
+  if (auto *decl = choice.getDeclOrNull()) {
     if (auto *CD = dyn_cast<ConstructorDecl>(decl)) {
       if (auto *fix = validateInitializerRef(cs, CD, locator))
         return fix;

lib/Sema/CSSolver.cpp

@@ -2104,11 +2104,9 @@ void ConstraintSystem::partitionDisjunction(
     forEachChoice(Choices, [&](unsigned index, Constraint *constraint) -> bool {
       if (constraint->getKind() != ConstraintKind::BindOverload)
         return false;
-      if (!constraint->getOverloadChoice().isDecl())
-        return false;
 
-      auto *decl = constraint->getOverloadChoice().getDecl();
-      auto *funcDecl = dyn_cast<FuncDecl>(decl);
+      auto *decl = constraint->getOverloadChoice().getDeclOrNull();
+      auto *funcDecl = dyn_cast_or_null<FuncDecl>(decl);
       if (!funcDecl)
         return false;
 

lib/Sema/ConstraintSystem.cpp

@@ -2134,8 +2134,7 @@ void ConstraintSystem::resolveOverload(ConstraintLocator *locator,
   }
   assert(!refType->hasTypeParameter() && "Cannot have a dependent type here");
 
-  if (choice.isDecl()) {
-    auto decl = choice.getDecl();
+  if (auto *decl = choice.getDeclOrNull()) {
     // If we're binding to an init member, the 'throws' need to line up between
     // the bound and reference types.
     if (auto CD = dyn_cast<ConstructorDecl>(decl)) {
@@ -2457,11 +2456,6 @@ bool ConstraintSystem::diagnoseAmbiguityWithFixes(
   if (solutions.empty())
     return false;
 
-  auto getOverloadDecl = [&](SelectedOverload &overload) -> ValueDecl * {
-    auto &choice = overload.choice;
-    return choice.isDecl() ? choice.getDecl() : nullptr;
-  };
-
   // Problems related to fixes forming ambiguous solution set
   // could only be diagnosed (at the moment), if all of the fixes
   // have the same callee locator, which means they fix different
@@ -2490,7 +2484,7 @@ bool ConstraintSystem::diagnoseAmbiguityWithFixes(
     if (!overload)
       return false;
 
-    auto *decl = getOverloadDecl(*overload);
+    auto *decl = overload->choice.getDeclOrNull();
     if (!decl)
       return false;
 

lib/Sema/OverloadChoice.h

@@ -244,6 +244,12 @@ class OverloadChoice {
     return DeclOrKind.get<ValueDecl*>();
   }
 
+  /// Retrieves the declaration that corresponds to this overload choice, or
+  /// \c nullptr if this choice is not for a declaration.
+  ValueDecl *getDeclOrNull() const {
+    return isDecl() ? getDecl() : nullptr;
+  }
+
   /// Returns true if this is either a decl for an optional that was
   /// declared as one that can be implicitly unwrapped, or is a
   /// function-typed decl that has a return value that is implicitly