[flang-commits] [flang] c66546b - [flang] Improve error message for polymorphic implicit interface (#177225)

[via flang-commits]

Author: Peter Klausler
Date: 2026-01-22T07:33:14-08:00
New Revision: c66546bfc8a28322664384f95794f910fc008630

URL: https://github.com/llvm/llvm-project/commit/c66546bfc8a28322664384f95794f910fc008630
DIFF: https://github.com/llvm/llvm-project/commit/c66546bfc8a28322664384f95794f910fc008630.diff

LOG: [flang] Improve error message for polymorphic implicit interface (#177225)

PROCEDURE(CLASS(...)) specifies a procedure with an implicit interface
whose result is polymorphic. That turns out to never be a valid
declaration, since a CLASS(...) function result is required to also be
POINTER or ALLOCATABLE, both of which require the presence of an
explicit interface. We caught this error already, but the message should
be improved for procedures.

Fixes https://github.com/llvm/llvm-project/issues/176861.

Added: 
    

Modified: 
    flang/lib/Semantics/check-declarations.cpp
    flang/test/Semantics/declarations06.f90

Removed: 
    


################################################################################
diff  --git a/flang/lib/Semantics/check-declarations.cpp b/flang/lib/Semantics/check-declarations.cpp
index 8a616f444b437..b50b71f28f790 100644
--- a/flang/lib/Semantics/check-declarations.cpp
+++ b/flang/lib/Semantics/check-declarations.cpp
@@ -3862,9 +3862,15 @@ void CheckHelper::CheckSymbolType(const Symbol &symbol) {
   } else if (auto dyType{evaluate::DynamicType::From(relevant)}) {
     if (dyType->IsPolymorphic() && !dyType->IsAssumedType() &&
         !(IsDummy(symbol) && !IsProcedure(relevant))) { // C708
-      messages_.Say(
-          "CLASS entity '%s' must be a dummy argument, allocatable, or object pointer"_err_en_US,
-          symbol.name());
+      if (IsProcedure(symbol)) {
+        messages_.Say(
+            "Polymorphic function%s '%s' must have an explicit interface whose result is ALLOCATABLE or POINTER"_err_en_US,
+            IsPointer(symbol) ? " pointer" : "", symbol.name());
+      } else {
+        messages_.Say(
+            "CLASS entity '%s' must be a dummy argument, allocatable, or object pointer"_err_en_US,
+            symbol.name());
+      }
     }
     if (dyType->HasDeferredTypeParameter()) { // C702
       messages_.Say(

diff  --git a/flang/test/Semantics/declarations06.f90 b/flang/test/Semantics/declarations06.f90
index ae9ef6acd7542..a490b8c3394fd 100644
--- a/flang/test/Semantics/declarations06.f90
+++ b/flang/test/Semantics/declarations06.f90
@@ -8,11 +8,11 @@ module m
   class(t) v1
   class(t), allocatable :: v2 ! ok
   class(t), pointer :: v3 ! ok
-  !ERROR: CLASS entity 'p1' must be a dummy argument, allocatable, or object pointer
+  !ERROR: Polymorphic function 'p1' must have an explicit interface whose result is ALLOCATABLE or POINTER
   procedure(cf1) :: p1
   procedure(cf2) :: p2
   procedure(cf3) :: p3
-  !ERROR: CLASS entity 'pp1' must be a dummy argument, allocatable, or object pointer
+  !ERROR: Polymorphic function pointer 'pp1' must have an explicit interface whose result is ALLOCATABLE or POINTER
   procedure(cf1), pointer :: pp1
   procedure(cf2), pointer :: pp2
   procedure(cf3), pointer :: pp3
@@ -29,9 +29,9 @@ class(t) function cf3()
   end
   subroutine test(d1,d2,d3)
     class(t) d1 ! ok
-    !ERROR: CLASS entity 'd2' must be a dummy argument, allocatable, or object pointer
+    !ERROR: Polymorphic function 'd2' must have an explicit interface whose result is ALLOCATABLE or POINTER
     class(t), external :: d2
-    !ERROR: CLASS entity 'd3' must be a dummy argument, allocatable, or object pointer
+    !ERROR: Polymorphic function pointer 'd3' must have an explicit interface whose result is ALLOCATABLE or POINTER
     class(t), external, pointer :: d3
   end
   function cf4()