[flang-commits] [flang] 3096b85 - [flang] Don't fold zero-length substring references

[Peter Klausler via flang-commits]

Author: Peter Klausler
Date: 2022-07-23T10:08:09-07:00
New Revision: 3096b85696cc71a6b6798c6883712f7ea6a6b576

URL: https://github.com/llvm/llvm-project/commit/3096b85696cc71a6b6798c6883712f7ea6a6b576
DIFF: https://github.com/llvm/llvm-project/commit/3096b85696cc71a6b6798c6883712f7ea6a6b576.diff

LOG: [flang] Don't fold zero-length substring references

In some contexts the code looks cleaner if we fold zero-length substring
references into empty character constants, but those don't work in
variable definition contexts and can lead to bogus semantic error
messages.

Differential Revision: https://reviews.llvm.org/D130383

Added: 
    

Modified: 
    flang/lib/Evaluate/fold-implementation.h

Removed: 
    


################################################################################
diff  --git a/flang/lib/Evaluate/fold-implementation.h b/flang/lib/Evaluate/fold-implementation.h
index daa3f0a6512d..37f4f8db996f 100644
--- a/flang/lib/Evaluate/fold-implementation.h
+++ b/flang/lib/Evaluate/fold-implementation.h
@@ -342,11 +342,9 @@ template <typename T> Expr<T> Folder<T>::Folding(Designator<T> &&designator) {
           return std::move(*specific);
         }
       }
-      if (auto length{ToInt64(Fold(context_, substring->LEN()))}) {
-        if (*length == 0) {
-          return Expr<T>{Constant<T>{Scalar<T>{}}};
-        }
-      }
+      // We used to fold zero-length substrings into zero-length
+      // constants here, but that led to problems in variable
+      // definition contexts.
     }
   } else if constexpr (T::category == TypeCategory::Real) {
     if (auto *zPart{std::get_if<ComplexPart>(&designator.u)}) {