Update DeclContext::getInnermostClosureForSelfCapture to return a ClosureExpr

Author: calda

include/swift/AST/DeclContext.h

@@ -82,6 +82,7 @@ namespace swift {
   class SerializedTopLevelCodeDecl;
   class StructDecl;
   class AccessorDecl;
+  class ClosureExpr;
 
   template <typename T>
   struct AvailableDuringLoweringDeclFilter;
@@ -507,8 +508,8 @@ class alignas(1 << DeclContextAlignInBits) DeclContext
   /// Returns the innermost context that is a ClosureExpr, which defines how
   /// self behaves, unless within a type context that redefines self.
   LLVM_READONLY
-  DeclContext *getInnermostClosureForSelfCapture();
-  const DeclContext *getInnermostClosureForSelfCapture() const {
+  ClosureExpr *getInnermostClosureForSelfCapture();
+  const ClosureExpr *getInnermostClosureForSelfCapture() const {
     return const_cast<DeclContext *>(this)->getInnermostClosureForSelfCapture();
   }
 

lib/AST/DeclContext.cpp

@@ -263,7 +263,7 @@ DeclContext *DeclContext::getInnermostSkippedFunctionContext() {
   return nullptr;
 }
 
-DeclContext *DeclContext::getInnermostClosureForSelfCapture() {
+ClosureExpr *DeclContext::getInnermostClosureForSelfCapture() {
   auto dc = this;
   if (auto closure = dyn_cast<ClosureExpr>(dc)) {
     return closure;

lib/AST/UnqualifiedLookup.cpp

@@ -355,8 +355,7 @@ ValueDecl *UnqualifiedLookupFactory::lookupBaseDecl(const DeclContext *baseDC) c
   // Perform an unqualified lookup for the base decl of this result. This
   // handles cases where self was rebound (e.g. `guard let self = self`)
   // earlier in this closure or some outer closure.
-  auto closureExpr =
-      dyn_cast_or_null<ClosureExpr>(DC->getInnermostClosureForSelfCapture());
+  auto closureExpr = DC->getInnermostClosureForSelfCapture();
   if (!closureExpr) {
     return nullptr;
   }

lib/Sema/MiscDiagnostics.cpp

@@ -2101,8 +2101,7 @@ static void diagnoseImplicitSelfUseInClosure(const Expr *E,
         return nullptr;
       }
 
-      return dyn_cast_or_null<const ClosureExpr>(
-          parentContext->getInnermostClosureForSelfCapture());
+      return parentContext->getInnermostClosureForSelfCapture();
     }
 
     bool shouldWalkCaptureInitializerExpressions() override { return true; }