[flang-commits] [flang] ca07ca0 - [flang] Fix confusing explanatory error message (#187341)

[via flang-commits]

Author: Peter Klausler
Date: 2026-03-18T17:04:47-05:00
New Revision: ca07ca0314bf93bd81a24a54ebfbb3cda607fe6b

URL: https://github.com/llvm/llvm-project/commit/ca07ca0314bf93bd81a24a54ebfbb3cda607fe6b
DIFF: https://github.com/llvm/llvm-project/commit/ca07ca0314bf93bd81a24a54ebfbb3cda607fe6b.diff

LOG: [flang] Fix confusing explanatory error message (#187341)

When a reference to a generic procedure fails, the compiler explains why
each of the generic's specific procedures failed to match the actual
arguments. This code had a subtle bug: adjustments to the actual
arguments made for interface checking for earlier specific procedures
would persist and affect the checks for later specific procedures.

Added: 
    flang/test/Semantics/bug2381.f90

Modified: 
    flang/include/flang/Semantics/expression.h
    flang/lib/Semantics/expression.cpp

Removed: 
    


################################################################################
diff  --git a/flang/include/flang/Semantics/expression.h b/flang/include/flang/Semantics/expression.h
index 490399aa03ff8..e2817ea542131 100644
--- a/flang/include/flang/Semantics/expression.h
+++ b/flang/include/flang/Semantics/expression.h
@@ -377,7 +377,7 @@ class ExpressionAnalyzer {
       const AdjustActuals &, bool isSubroutine, SymbolVector &&tried,
       bool mightBeStructureConstructor = false);
   void EmitGenericResolutionError(const Symbol &, bool dueToNullActuals,
-      bool isSubroutine, ActualArguments &, const SymbolVector &,
+      bool isSubroutine, const ActualArguments &, const SymbolVector &,
       const AdjustActuals &);
   const Symbol &AccessSpecific(
       const Symbol &originalGeneric, const Symbol &specific);

diff  --git a/flang/lib/Semantics/expression.cpp b/flang/lib/Semantics/expression.cpp
index 457c5a3594f6d..2d7c32fd5fb8f 100644
--- a/flang/lib/Semantics/expression.cpp
+++ b/flang/lib/Semantics/expression.cpp
@@ -3144,7 +3144,7 @@ const Symbol &ExpressionAnalyzer::AccessSpecific(
 }
 
 void ExpressionAnalyzer::EmitGenericResolutionError(const Symbol &symbol,
-    bool dueToAmbiguity, bool isSubroutine, ActualArguments &arguments,
+    bool dueToAmbiguity, bool isSubroutine, const ActualArguments &arguments,
     const SymbolVector &tried, const AdjustActuals &adjustment) {
   if (auto *msg{Say(dueToAmbiguity
               ? "The actual arguments to the generic procedure '%s' matched multiple specific procedures, perhaps due to use of NULL() without MOLD= or an actual procedure with an implicit interface"_err_en_US
@@ -3158,16 +3158,12 @@ void ExpressionAnalyzer::EmitGenericResolutionError(const Symbol &symbol,
       if (auto procChars{characteristics::Procedure::Characterize(
               specific, GetFoldingContext())}) {
         if (procChars->HasExplicitInterface()) {
-          ActualArguments *actuals{&arguments};
-          ActualArguments adjustedActuals;
+          ActualArguments adjusted{arguments};
           if (specific.has<semantics::ProcBindingDetails>() &&
               adjustment.has_value()) {
-            adjustedActuals = arguments;
-            if ((*adjustment)(specific, adjustedActuals)) {
-              actuals = &adjustedActuals;
-            }
+            (*adjustment)(specific, adjusted);
           }
-          auto reasons{semantics::CheckExplicitInterface(*procChars, *actuals,
+          auto reasons{semantics::CheckExplicitInterface(*procChars, adjusted,
               context_, /*scope=*/nullptr, /*intrinsic=*/nullptr,
               /*allocActualArgumentConversions=*/false,
               /*extentErrors=*/false,

diff  --git a/flang/test/Semantics/bug2381.f90 b/flang/test/Semantics/bug2381.f90
new file mode 100644
index 0000000000000..86f8d915b9830
--- /dev/null
+++ b/flang/test/Semantics/bug2381.f90
@@ -0,0 +1,17 @@
+!RUN: not %flang_fc1 -fsyntax-only %s 2>&1 | FileCheck %s
+module m
+  generic :: gen => spec2, spec1
+ contains
+  subroutine spec2(a,b)
+    real, intent(in) :: a(*), b(*)
+  end
+  subroutine spec1(a)
+    real, intent(in) :: a(:)
+  end
+  subroutine test(a)
+    real, intent(in) :: a(*)
+!CHECK: Dummy argument 'b=' (#2) is not OPTIONAL and is not associated with an actual argument in this procedure reference
+!CHECK: Assumed-size array may not be associated with assumed-shape dummy argument 'a='
+    call gen(a)
+  end
+end