Fixes crash instrumenting generic func body nested in another func

lib/Sema/PCMacro.cpp

@@ -339,7 +339,12 @@ class Instrumenter : InstrumenterBase {
     if (auto *FD = dyn_cast<FuncDecl>(D)) {
       if (BraceStmt *B = FD->getTypecheckedBody()) {
         const ParameterList *PL = FD->getParameters();
+
+        // Use FD's DeclContext as TypeCheckDC for transforms in func body
+        // then swap back TypeCheckDC at end of scope.
+        llvm::SaveAndRestore<DeclContext *> localDC(TypeCheckDC, FD);
         BraceStmt *NB = transformBraceStmt(B, PL);
+
         // Since it would look strange going straight to the first line in a
         // function body, we throw in a before/after pointing at the function
         // decl at the start of the transformed body

lib/Sema/PlaygroundTransform.cpp

@@ -312,6 +312,11 @@ class Instrumenter : InstrumenterBase {
       if (BraceStmt *B = FD->getTypecheckedBody()) {
         const ParameterList *PL = FD->getParameters();
         TargetKindSetter TKS(BracePairs, BracePair::TargetKinds::Return);
+
+        // Use FD's DeclContext as TypeCheckDC for transforms in func body
+        // then swap back TypeCheckDC at end of scope.
+        llvm::SaveAndRestore<DeclContext *> localDC(TypeCheckDC, FD);
+
         BraceStmt *NB = transformBraceStmt(B, PL);
         if (NB != B) {
           FD->setBody(NB, AbstractFunctionDecl::BodyKind::TypeChecked);

test/PlaygroundTransform/generic_func_in_local_scope.swift

@@ -0,0 +1,33 @@
+// RUN: %empty-directory(%t)
+
+// Build PlaygroundSupport module
+// RUN: %target-build-swift -whole-module-optimization -module-name PlaygroundSupport -emit-module-path %t/PlaygroundSupport.swiftmodule -parse-as-library -c -o %t/PlaygroundSupport.o %S/Inputs/SilentPCMacroRuntime.swift %S/Inputs/PlaygroundsRuntime.swift
+
+// RUN: %target-build-swift -swift-version 5 -emit-module -Xfrontend -playground -I=%t %s
+// RUN: %target-build-swift -swift-version 6 -emit-module -Xfrontend -playground -I=%t %s
+
+// RUN: %target-build-swift -swift-version 5 -emit-module -Xfrontend -playground -Xfrontend -pc-macro -I=%t %s
+// RUN: %target-build-swift -swift-version 6 -emit-module -Xfrontend -playground -Xfrontend -pc-macro -I=%t %s
+
+// REQUIRES: executable_test
+
+import PlaygroundSupport
+
+func test1() {
+    func buildBlock<Content>(content: Content) {
+        content
+    }
+}
+
+func test2() {
+    func buildBlock<Content>(content: Content) -> Content {
+        content
+        return content
+    }
+}
+
+func test3<Content>(_ content: Content) {
+    func buildBlock<Content2>(_ content2: Content2) -> Content2 {
+       return content2
+    }
+}