[flang] Submodule names can clash only with submodule names

[klausler]

Name resolution creates symbols for submodules in their parents' scopes. This can lead to bogus errors about name clashes between submodule names and other entities in the parents' scopes.

Create symbols for submodules but do not add them to a scope's dictionary.

[llvmbot]

@llvm/pr-subscribers-flang-semantics

Changes

Name resolution creates symbols for submodules in their parents' scopes. This can lead to bogus errors about name clashes between submodule names and other entities in the parents' scopes.

Create symbols for submodules but do not add them to a scope's dictionary.

---

Full diff: https://github.com/llvm/llvm-project/pull/67361.diff

4 Files Affected:

• (modified) flang/lib/Semantics/mod-file.cpp (+31-12)
• (modified) flang/lib/Semantics/resolve-names.cpp (+5-1)
• (modified) flang/test/Semantics/modproc01.f90 (+3-1)
• (modified) flang/test/Semantics/modproc02.f90 (-1)

diff --git a/flang/lib/Semantics/mod-file.cpp b/flang/lib/Semantics/mod-file.cpp
index 15d6f62f706c922..6eeb7bb7542b150 100644
--- a/flang/lib/Semantics/mod-file.cpp
+++ b/flang/lib/Semantics/mod-file.cpp
@@ -1175,30 +1175,49 @@ Scope *ModFileReader::Read(const SourceName &name,
   }
   Scope &topScope{isIntrinsic.value_or(false) ? context_.intrinsicModulesScope()
                                               : context_.globalScope()};
-  if (!ancestor) {
+  Symbol *moduleSymbol{nullptr};
+  if (!ancestor) { // module, not submodule
     parentScope = &topScope;
+    auto pair{parentScope->try_emplace(name, UnknownDetails{})};
+    if (!pair.second) {
+      return nullptr;
+    }
+    moduleSymbol = &*pair.first->second;
+    moduleSymbol->set(Symbol::Flag::ModFile);
   } else if (std::optional<SourceName> parent{GetSubmoduleParent(parseTree)}) {
+    // submodule with submodule parent
     parentScope = Read(*parent, false /*not intrinsic*/, ancestor, silent);
   } else {
+    // submodule with module parent
     parentScope = ancestor;
   }
-  auto pair{parentScope->try_emplace(name, UnknownDetails{})};
-  if (!pair.second) {
-    return nullptr;
-  }
   // Process declarations from the module file
-  Symbol &modSymbol{*pair.first->second};
-  modSymbol.set(Symbol::Flag::ModFile);
   bool wasInModuleFile{context_.foldingContext().inModuleFile()};
   context_.foldingContext().set_inModuleFile(true);
   ResolveNames(context_, parseTree, topScope);
   context_.foldingContext().set_inModuleFile(wasInModuleFile);
-  CHECK(modSymbol.has<ModuleDetails>());
-  CHECK(modSymbol.test(Symbol::Flag::ModFile));
-  if (isIntrinsic.value_or(false)) {
-    modSymbol.attrs().set(Attr::INTRINSIC);
+  if (!moduleSymbol) {
+    // Submodule symbols' storage are owned by their parents' scopes,
+    // but their names are not in their parents' dictionaries -- we
+    // don't want to report bogus errors about clashes between submodule
+    // names and other objects in the parent scopes.
+    if (Scope * submoduleScope{ancestor->FindSubmodule(name)}) {
+      moduleSymbol = submoduleScope->symbol();
+      if (moduleSymbol) {
+        moduleSymbol->set(Symbol::Flag::ModFile);
+      }
+    }
+  }
+  if (moduleSymbol) {
+    CHECK(moduleSymbol->has<ModuleDetails>());
+    CHECK(moduleSymbol->test(Symbol::Flag::ModFile));
+    if (isIntrinsic.value_or(false)) {
+      moduleSymbol->attrs().set(Attr::INTRINSIC);
+    }
+    return moduleSymbol->scope();
+  } else {
+    return nullptr;
   }
-  return modSymbol.scope();
 }
 
 parser::Message &ModFileReader::Say(const SourceName &name,
diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index 47ecaa1b82e53ed..b79f0989d46a2ec 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -3219,7 +3219,11 @@ bool ModuleVisitor::BeginSubmodule(
 }
 
 void ModuleVisitor::BeginModule(const parser::Name &name, bool isSubmodule) {
-  auto &symbol{MakeSymbol(name, ModuleDetails{isSubmodule})};
+  // Submodule symbols are not visible in their parents' scopes.
+  Symbol &symbol{isSubmodule ? Resolve(name,
+                                   currScope().MakeSymbol(name.source, Attrs{},
+                                       ModuleDetails{true}))
+                             : MakeSymbol(name, ModuleDetails{false})};
   auto &details{symbol.get<ModuleDetails>()};
   PushScope(Scope::Kind::Module, &symbol);
   details.set_scope(&currScope());
diff --git a/flang/test/Semantics/modproc01.f90 b/flang/test/Semantics/modproc01.f90
index c7d05783335e699..5652e15750c7e90 100644
--- a/flang/test/Semantics/modproc01.f90
+++ b/flang/test/Semantics/modproc01.f90
@@ -22,11 +22,12 @@ module subroutine ms(f)
       procedure(mf) :: f
     end subroutine
   end interface
+  integer sm
 end module
 !CHECK:    mf, MODULE, PUBLIC (Function): Subprogram isInterface result:TYPE(pdt2(k2=2_4,l2=n)) res (INTEGER(4) n,CHARACTER(n,1) str,TYPE(pdt1(k1=1_4,l1=n)) x1)
 !CHECK:    pdt1, PUBLIC: DerivedType components: a1
 !CHECK:    pdt2, PUBLIC: DerivedType components: j2,a2
-!CHECK:    sm: Module (m)
+!CHECK:    sm, PUBLIC size=4 offset=0: ObjectEntity type: INTEGER(4)
 !CHECK:    DerivedType scope: pdt1
 !CHECK:      a1, ALLOCATABLE: ObjectEntity type: TYPE(pdt2(int(k1,kind=4),int(l1,kind=4)))
 !CHECK:      k1: TypeParam type:INTEGER(4) Kind
@@ -128,6 +129,7 @@ program test
 !CHECK:    mf, MODULE (Function): Use from mf in m
 !CHECK:    pdt1: Use from pdt1 in m
 !CHECK:    pdt2: Use from pdt2 in m
+!CHECK:    sm: Use from sm in m
 !CHECK:    x size=88 offset=0: ObjectEntity type: TYPE(pdt2(k2=2_4,l2=3_4))
 !CHECK:    DerivedType scope: size=88 alignment=8 instantiation of pdt2(k2=2_4,l2=3_4)
 !CHECK:      a2 size=80 offset=8: ObjectEntity type: TYPE(pdt1(k1=2_4,l1=3_4)) shape: 1_8:2_8
diff --git a/flang/test/Semantics/modproc02.f90 b/flang/test/Semantics/modproc02.f90
index 229ef72e6bcf049..f47f473f081d2f8 100644
--- a/flang/test/Semantics/modproc02.f90
+++ b/flang/test/Semantics/modproc02.f90
@@ -16,7 +16,6 @@ module subroutine s(x) ! implicitly typed
 
 !CHECK:  Module scope: m size=0 alignment=1 sourceRange=63 bytes
 !CHECK:    s, MODULE, PUBLIC (Subroutine): Subprogram isInterface (REAL(4) x)
-!CHECK:    sm: Module (m)
 !CHECK:    Subprogram scope: s size=4 alignment=4 sourceRange=26 bytes
 !CHECK:      s (Subroutine): HostAssoc
 !CHECK:      x (Implicit) size=4 offset=0: ObjectEntity dummy type: REAL(4)