[flang-commits] [flang] [Flang][Semantics] Diagnose missing MODULE prefix in submodule procedures (PR #197173)

[Eugene Epshteyn via flang-commits]

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@@ -5976,6 +5976,26 @@ const Symbol *SubprogramVisitor::CheckExtantProc(
 Symbol *SubprogramVisitor::PushSubprogramScope(const parser::Name &name,
     Symbol::Flag subpFlag, const parser::LanguageBindingSpec *bindingSpec,
     bool hasModulePrefix) {
+  if (!inInterfaceBlock() && currScope().IsSubmodule() && !hasModulePrefix) {
+    const Scope &parent{currScope().parent()};
+    if (parent.IsModule() || parent.IsSubmodule()) {
+      if (const Symbol *host{parent.FindSymbol(name.source)}) {
+        const Symbol &hostUlt{host->GetUltimate()};
+        const auto *hostSubp{hostUlt.detailsIf<SubprogramDetails>()};
+        if (hostSubp && hostSubp->isInterface() &&
+            hostUlt.attrs().test(Attr::MODULE)) {
+          context().messages().Warn(/*isInModuleFile=*/InModuleFile(),
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eugeneepshteyn wrote:

A short comment on the context().messages().Warn(...) call explaining why it bypasses SemanticsContext::Warn (module-file scope-ancestry suppression) would protect it from a future "simplification" back to context().Warn — fold-integer.cpp carries such a comment at its analogous call.

https://github.com/llvm/llvm-project/pull/197173