[flang] USE-associated explicit INTRINSIC names

[klausler]

The compiler doesn't USE-associate names of intrinsic procedures from modules (in the absence of ONLY:), so that the associating scope doesn't get populated with names of intrinsics that were used only in declarations (e.g., SELECTED_REAL_KIND). A recent bug report (below) shows that we should modify that policy in the case of names that appear in explicit INTRINSIC attribute statements. The behaviors of other Fortran compilers are not consistent and the requirements of the standard are not clear; this fix follows the precedent set by gfortran and nvfortran.

Fixes #72084.

[llvmbot]

@llvm/pr-subscribers-flang-semantics

Author: Peter Klausler (klausler)

Changes

The compiler doesn't USE-associate names of intrinsic procedures from modules (in the absence of ONLY:), so that the associating scope doesn't get populated with names of intrinsics that were used only in declarations (e.g., SELECTED_REAL_KIND). A recent bug report (below) shows that we should modify that policy in the case of names that appear in explicit INTRINSIC attribute statements. The behaviors of other Fortran compilers are not consistent and the requirements of the standard are not clear; this fix follows the precedent set by gfortran and nvfortran.

Fixes #72084.

---

Full diff: https://github.com/llvm/llvm-project/pull/76199.diff

3 Files Affected:

• (modified) flang/docs/Extensions.md (+4)
• (modified) flang/lib/Semantics/resolve-names.cpp (+5-5)
• (added) flang/test/Semantics/intrinsics02.f90 (+16)

diff --git a/flang/docs/Extensions.md b/flang/docs/Extensions.md
index 03d4310466485c..6c6588025a392d 100644
--- a/flang/docs/Extensions.md
+++ b/flang/docs/Extensions.md
@@ -641,6 +641,10 @@ module m
 end
 ```
 
+* When an intrinsic procedure appears in the specification part of a module
+  only in function references, but not an explicit `INTRINSIC` statement,
+  its name is not brought into other scopes by a `USE` statement.
+
 ## De Facto Standard Features
 
 * `EXTENDS_TYPE_OF()` returns `.TRUE.` if both of its arguments have the
diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index e1cd34ddf65b6b..73f240abc95b7b 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -2904,7 +2904,7 @@ void ModuleVisitor::Post(const parser::UseStmt &x) {
     }
     for (const auto &[name, symbol] : *useModuleScope_) {
       if (symbol->attrs().test(Attr::PUBLIC) && !IsUseRenamed(symbol->name()) &&
-          (!symbol->attrs().test(Attr::INTRINSIC) ||
+          (!symbol->implicitAttrs().test(Attr::INTRINSIC) ||
               symbol->has<UseDetails>()) &&
           !symbol->has<MiscDetails>() && useNames.count(name) == 0) {
         SourceName location{x.moduleName.source};
@@ -6244,8 +6244,8 @@ bool DeclarationVisitor::HandleUnrestrictedSpecificIntrinsicFunction(
     // recreated for it later on demand, but capturing its result type here
     // will make GetType() return a correct result without having to
     // probe the intrinsics table again.
-    Symbol &symbol{
-        MakeSymbol(InclusiveScope(), name.source, Attrs{Attr::INTRINSIC})};
+    Symbol &symbol{MakeSymbol(InclusiveScope(), name.source, Attrs{})};
+    SetImplicitAttr(symbol, Attr::INTRINSIC);
     CHECK(interface->functionResult.has_value());
     evaluate::DynamicType dyType{
         DEREF(interface->functionResult->GetTypeAndShape()).type()};
@@ -7708,8 +7708,8 @@ void ResolveNamesVisitor::HandleProcedureName(
   auto *symbol{FindSymbol(NonDerivedTypeScope(), name)};
   if (!symbol) {
     if (IsIntrinsic(name.source, flag)) {
-      symbol =
-          &MakeSymbol(InclusiveScope(), name.source, Attrs{Attr::INTRINSIC});
+      symbol = &MakeSymbol(InclusiveScope(), name.source, Attrs{});
+      SetImplicitAttr(*symbol, Attr::INTRINSIC);
     } else if (const auto ppcBuiltinScope =
                    currScope().context().GetPPCBuiltinsScope()) {
       // Check if it is a builtin from the predefined module
diff --git a/flang/test/Semantics/intrinsics02.f90 b/flang/test/Semantics/intrinsics02.f90
new file mode 100644
index 00000000000000..1b8dc4f34ba69c
--- /dev/null
+++ b/flang/test/Semantics/intrinsics02.f90
@@ -0,0 +1,16 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+module explicit
+  intrinsic cos
+end
+subroutine testExplicit
+  use explicit
+  !ERROR: 'cos' is use-associated from module 'explicit' and cannot be re-declared
+  real :: cos = 2.
+end
+module implicit
+  real :: one = cos(0.)
+end
+subroutine testImplicit
+  use implicit
+  real :: cos = 2.
+end

[ceseo]

LGTM.