[flang] Fix scope accessibility check

The check for whether a private component is accessible was depending on
determining whether the source range of the current scope was within the
source range of the module that the component was declared in. This
could fail if the current scope was of kind `ImpliedDos` and had no
source range.

The fix is to add `Scope::Contains` to check the relationship by
traversing the parent links. These are created when the Scope is so are
always reliable. The source range of a scope is built up over time.

Original-commit: flang-compiler/f18@d787108637
Reviewed-on: https://github.com/flang-compiler/f18/pull/1060

flang/include/flang/Semantics/scope.h

@@ -85,15 +85,8 @@ public:
 
   const Symbol *GetSymbol() const;
   const Scope *GetDerivedTypeParent() const;
-
-  std::optional<SourceName> GetName() const {
-    if (const auto *sym{GetSymbol()}) {
-      return sym->name();
-    } else {
-      return std::nullopt;
-    }
-  }
-
+  std::optional<SourceName> GetName() const;
+  bool Contains(const Scope &) const;
   /// Make a scope nested in this one
   Scope &MakeScope(Kind kind, Symbol *symbol = nullptr);
 

flang/lib/Semantics/scope.cpp

@@ -91,6 +91,25 @@ Symbol *Scope::FindComponent(SourceName name) const {
   }
 }
 
+std::optional<SourceName> Scope::GetName() const {
+  if (const auto *sym{GetSymbol()}) {
+    return sym->name();
+  } else {
+    return std::nullopt;
+  }
+}
+
+bool Scope::Contains(const Scope &that) const {
+  for (const Scope *scope{&that};; scope = &scope->parent()) {
+    if (*scope == *this) {
+      return true;
+    }
+    if (scope->IsGlobal()) {
+      return false;
+    }
+  }
+}
+
 const std::list<EquivalenceSet> &Scope::equivalenceSets() const {
   return equivalenceSets_;
 }
@@ -244,8 +263,7 @@ Scope *Scope::FindScope(parser::CharBlock source) {
 }
 
 void Scope::AddSourceRange(const parser::CharBlock &source) {
-  for (auto *scope = this; !scope->IsGlobal();
-       scope = &scope->parent()) {
+  for (auto *scope = this; !scope->IsGlobal(); scope = &scope->parent()) {
     scope->sourceRange_.ExtendToCover(source);
   }
 }

flang/lib/Semantics/tools.cpp

@@ -960,7 +960,7 @@ std::optional<parser::MessageFormattedText> CheckAccessibleComponent(
   CHECK(symbol.owner().IsDerivedType());  // symbol must be a component
   if (symbol.attrs().test(Attr::PRIVATE)) {
     if (const Scope * moduleScope{FindModuleContaining(symbol.owner())}) {
-      if (!moduleScope->sourceRange().Contains(scope.sourceRange())) {
+      if (!moduleScope->Contains(scope)) {
         return parser::MessageFormattedText{
             "PRIVATE component '%s' is only accessible within module '%s'"_err_en_US,
             symbol.name(), moduleScope->GetName().value()};

flang/test/Semantics/resolve34.f90

@@ -98,11 +98,16 @@ module m8
     integer :: i1
     integer, private :: i2
   end type
+  type(t) :: y
+  integer :: a(1)
 contains
   subroutine s0
     type(t) :: x
     x = t(i1=2, i2=5)  !OK
   end
+  subroutine s1
+    a = [y%i2]  !OK
+  end subroutine
 end
 subroutine s8
   use m8
@@ -111,6 +116,8 @@ subroutine s8
   x = t(2, 5)
   !ERROR: PRIVATE component 'i2' is only accessible within module 'm8'
   x = t(i1=2, i2=5)
+  !ERROR: PRIVATE component 'i2' is only accessible within module 'm8'
+  a = [y%i2]
 end
 
 ! 7.5.4.8(2)