[flang] Improve error messages about overflowed integer conversions

[klausler]

When an INTEGER conversion to a smaller kind overflows in constant folding, report the truncated value so that it makes more sense later if it shows up in other messages.

[llvmbot]

@llvm/pr-subscribers-flang-semantics

Author: Peter Klausler (klausler)

Changes

When an INTEGER conversion to a smaller kind overflows in constant folding, report the truncated value so that it makes more sense later if it shows up in other messages.

---

Full diff: https://github.com/llvm/llvm-project/pull/110031.diff

2 Files Affected:

• (modified) flang/lib/Evaluate/fold-implementation.h (+3-2)
• (modified) flang/test/Evaluate/errors01.f90 (+2)

diff --git a/flang/lib/Evaluate/fold-implementation.h b/flang/lib/Evaluate/fold-implementation.h
index 1b14a305b87f4f..89477dfb364351 100644
--- a/flang/lib/Evaluate/fold-implementation.h
+++ b/flang/lib/Evaluate/fold-implementation.h
@@ -1736,8 +1736,9 @@ Expr<TO> FoldOperation(
                   msvcWorkaround.context.languageFeatures().ShouldWarn(
                       common::UsageWarning::FoldingException)) {
                 ctx.messages().Say(
-                    "INTEGER(%d) to INTEGER(%d) conversion overflowed"_warn_en_US,
-                    Operand::kind, TO::kind);
+                    "conversion of %s_%d to INTEGER(%d) overflowed; result is %s"_warn_en_US,
+                    value->SignedDecimal(), Operand::kind, TO::kind,
+                    converted.value.SignedDecimal());
               }
               return ScalarConstantToExpr(std::move(converted.value));
             } else if constexpr (FromCat == TypeCategory::Real) {
diff --git a/flang/test/Evaluate/errors01.f90 b/flang/test/Evaluate/errors01.f90
index bad73f2e8b160f..684f3fc34e6872 100644
--- a/flang/test/Evaluate/errors01.f90
+++ b/flang/test/Evaluate/errors01.f90
@@ -192,6 +192,8 @@ subroutine warnings
     real, parameter :: bad10 = product([huge(1.),huge(1.)])
     !CHECK: warning: PRODUCT() of COMPLEX(4) data overflowed
     complex, parameter :: bad11 = product([(huge(1.),0.),(huge(1.),0.)])
+    !CHECK: warning: conversion of 111111111111111111111_16 to INTEGER(8) overflowed; result is 430646668853801415
+    integer(8), parameter :: bad12 = int(111111111111111111111, 8)
     !CHECK: warning: overflow on REAL(8) to REAL(4) conversion
     x = 1.D40
     !CHECK-NOT: warning: invalid argument

[tarunprabhu]

LGTM. Thanks!