[SEH] Fix regression with SEH in noexpect functions

Commit 5baea05601 set the CurCodeDecl
because it was needed to pass the assert in CodeGenFunction::EmitLValueForLambdaField,
But this was not right to do as CodeGenFunction::FinishFunction passes it to EmitEndEHSpec
and cause corruption of the EHStack.

Revert the part of the commit that changes the CurCodeDecl, and instead
adjust the assert to check for a null CurCodeDecl.

Differential Revision: https://reviews.llvm.org/D102027

clang/lib/CodeGen/CGException.cpp

@@ -1966,7 +1966,6 @@ void CodeGenFunction::startOutlinedSEHHelper(CodeGenFunction &ParentCGF,
   StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args,
                 OutlinedStmt->getBeginLoc(), OutlinedStmt->getBeginLoc());
   CurSEHParent = ParentCGF.CurSEHParent;
-  CurCodeDecl = ParentCGF.CurCodeDecl;
 
   CGM.SetInternalFunctionAttributes(GlobalDecl(), CurFn, FnInfo);
   EmitCapturedLocals(ParentCGF, OutlinedStmt, IsFilter);

clang/lib/CodeGen/CGExpr.cpp

@@ -4185,8 +4185,10 @@ LValue CodeGenFunction::EmitMemberExpr(const MemberExpr *E) {
 /// Given that we are currently emitting a lambda, emit an l-value for
 /// one of its members.
 LValue CodeGenFunction::EmitLValueForLambdaField(const FieldDecl *Field) {
-  assert(cast<CXXMethodDecl>(CurCodeDecl)->getParent()->isLambda());
-  assert(cast<CXXMethodDecl>(CurCodeDecl)->getParent() == Field->getParent());
+  if (CurCodeDecl) {
+    assert(cast<CXXMethodDecl>(CurCodeDecl)->getParent()->isLambda());
+    assert(cast<CXXMethodDecl>(CurCodeDecl)->getParent() == Field->getParent());
+  }
   QualType LambdaTagType =
     getContext().getTagDeclType(Field->getParent());
   LValue LambdaLV = MakeNaturalAlignAddrLValue(CXXABIThisValue, LambdaTagType);

clang/test/CodeGenCXX/exceptions-seh.cpp

@@ -164,3 +164,5 @@ void use_inline() {
 // CHECK: store i32 1234, i32* @my_unique_global
 
 // CHECK: attributes #[[NOINLINE]] = { {{.*noinline.*}} }
+
+void seh_in_noexcept() noexcept { __try {} __finally {} }