[flang] Don't emit conversion error for max(a,b, optionalCharacter)

[klausler]

A recent patch added an error message for whole optional dummy argument usage as optional arguments (third or later) to MAX and MIN when those names required type conversion, since that conversion only works when the optional arguments are present. This check shouldn't care about character lengths. Make it so.

[llvmbot]

@llvm/pr-subscribers-flang-semantics

Author: Peter Klausler (klausler)

Changes

A recent patch added an error message for whole optional dummy argument usage as optional arguments (third or later) to MAX and MIN when those names required type conversion, since that conversion only works when the optional arguments are present. This check shouldn't care about character lengths. Make it so.

---

Full diff: https://github.com/llvm/llvm-project/pull/88156.diff

1 Files Affected:

• (modified) flang/lib/Semantics/check-call.cpp (+9-4)

diff --git a/flang/lib/Semantics/check-call.cpp b/flang/lib/Semantics/check-call.cpp
index bd2f755855172a..7d73b55dac328e 100644
--- a/flang/lib/Semantics/check-call.cpp
+++ b/flang/lib/Semantics/check-call.cpp
@@ -1477,10 +1477,15 @@ static void CheckMaxMin(const characteristics::Procedure &proc,
         if (arguments[j]) {
           if (const auto *expr{arguments[j]->UnwrapExpr()};
               expr && evaluate::MayBePassedAsAbsentOptional(*expr)) {
-            if (auto thisType{expr->GetType()};
-                thisType && *thisType != typeAndShape->type()) {
-              messages.Say(arguments[j]->sourceLocation(),
-                  "An actual argument to MAX/MIN requiring data conversion may not be OPTIONAL, POINTER, or ALLOCATABLE"_err_en_US);
+            if (auto thisType{expr->GetType()}) {
+              if (thisType->category() == TypeCategory::Character &&
+                  typeAndShape->type().category() == TypeCategory::Character &&
+                  thisType->kind() == typeAndShape->type().kind()) {
+                // don't care about lengths
+              } else if (*thisType != typeAndShape->type()) {
+                messages.Say(arguments[j]->sourceLocation(),
+                    "An actual argument to MAX/MIN requiring data conversion may not be OPTIONAL, POINTER, or ALLOCATABLE"_err_en_US);
+              }
             }
           }
         }

[psteinfeld]

Thanks for the quick fix!

All builds and tests correctly and looks good.