[flang][preprocessor] Finesse disabling of function-like macros

flang/lib/Parser/preprocessor.cpp

@@ -397,9 +397,9 @@ std::optional<TokenSequence> Preprocessor::MacroReplacement(
           (n + 1 == argStart.size() ? k : argStart[n + 1] - 1) - at};
       args.emplace_back(TokenSequence(input, at, count));
     }
+    TokenSequence applied{def->Apply(args, prescanner)};
     def->set_isDisabled(true);
-    TokenSequence replaced{
-        ReplaceMacros(def->Apply(args, prescanner), prescanner)};
+    TokenSequence replaced{ReplaceMacros(std::move(applied), prescanner)};
     def->set_isDisabled(false);
     if (!replaced.empty()) {
       ProvenanceRange from{def->replacement().GetProvenanceRange()};

flang/lib/Semantics/check-call.cpp

@@ -1274,11 +1274,15 @@ static void CheckAssociated(evaluate::ActualArguments &arguments,
         return;
       }
       if (const auto &targetArg{arguments[1]}) {
-        // The standard requires that the POINTER= argument be a valid LHS for
-        // a pointer assignment when the TARGET= argument is present.  This,
-        // perhaps unintentionally, excludes function results, including NULL(),
-        // from being used there, as well as INTENT(IN) dummy pointers.
-        // Allow this usage as a benign extension with a portability warning.
+        // The standard requires that the TARGET= argument, when present,
+        // be a valid RHS for a pointer assignment that has the POINTER=
+        // argument as its LHS.  Some popular compilers misinterpret this
+        // requirement more strongly than necessary, and actually validate
+        // the POINTER= argument as if it were serving as the LHS of a pointer
+        // assignment.  This, perhaps unintentionally, excludes function
+        // results, including NULL(), from being used there, as well as
+        // INTENT(IN) dummy pointers.  Detect these conditions and emit
+        // portability warnings.
         if (!evaluate::ExtractDataRef(*pointerExpr) &&
             !evaluate::IsProcedurePointer(*pointerExpr)) {
           context.messages().Say(pointerArg->sourceLocation(),

flang/test/Preprocessing/disable-expansion.F90

@@ -0,0 +1,14 @@
+! RUN: %flang -E %s | FileCheck %s
+#define KWM a
+#define FLM(x) b FLM2(x) KWM c
+#define FLM2(x) d FLM(x) e
+! CHECK: a
+KWM
+! CHECK: b d FLM(y) e a c
+FLM(y)
+! CHECK: b d FLM(a) e a c
+FLM(KWM)
+! CHECK: b d FLM(b d FLM(y) e a c) e a c
+FLM(FLM(y))
+! CHECK: b d FLM(b d FLM(a) e a c) e a c
+FLM(FLM(KWM))