[flang] silence bogus error with BIND(C) variable in hermetic module (#143737)

The global name semantic check was firing in a bogus way when BIND(C)
variables are in hermetic module.

Do not raise the error if one of the symbol with the conflicting global
name is an "hermetic variant" of the other.

Author: jeanPerier

flang/lib/Semantics/check-declarations.cpp

@@ -2958,6 +2958,14 @@ static std::optional<std::string> DefinesGlobalName(const Symbol &symbol) {
   return std::nullopt;
 }
 
+static bool IsSameSymbolFromHermeticModule(
+    const Symbol &symbol, const Symbol &other) {
+  return symbol.name() == other.name() && symbol.owner().IsModule() &&
+      other.owner().IsModule() && symbol.owner() != other.owner() &&
+      symbol.owner().GetName() &&
+      symbol.owner().GetName() == other.owner().GetName();
+}
+
 // 19.2 p2
 void CheckHelper::CheckGlobalName(const Symbol &symbol) {
   if (auto global{DefinesGlobalName(symbol)}) {
@@ -2975,6 +2983,8 @@ void CheckHelper::CheckGlobalName(const Symbol &symbol) {
           (!IsExternalProcedureDefinition(symbol) ||
               !IsExternalProcedureDefinition(other))) {
         // both are procedures/BLOCK DATA, not both definitions
+      } else if (IsSameSymbolFromHermeticModule(symbol, other)) {
+        // Both symbols are the same thing.
       } else if (symbol.has<ModuleDetails>()) {
         Warn(common::LanguageFeature::BenignNameClash, symbol.name(),
             "Module '%s' conflicts with a global name"_port_en_US,

flang/test/Semantics/modfile76.F90

@@ -0,0 +1,24 @@
+!RUN: %flang_fc1 -fsyntax-only -fhermetic-module-files -DSTEP=1 %s
+!RUN: %flang_fc1 -fsyntax-only %s
+
+! Tests that a BIND(C) variable in a module A captured in a hermetic module
+! file USE'd in a module B is not creating bogus complaints about BIND(C) name
+! conflict when both module A and B are later accessed.
+
+#if STEP == 1
+module modfile75a
+  integer, bind(c) :: x
+end
+
+module modfile75b
+  use modfile75a ! capture hermetically
+end
+
+#else
+subroutine test
+  use modfile75a
+  use modfile75b
+  implicit none
+  print *, x
+end subroutine
+#endif