[flang] Implement cross-set EQUIVALENCE impossibility checking

Implement cross-set EQUIVALENCE impossibility checking; fixes
an infinite loop on an erroneous test.  Also fix substring
reference offset calculations in EQUIVALENCE discovered to
be incorrect during testing.

Reviewed By: tskeith

Differential Revision: https://reviews.llvm.org/D82993

1 files changed, 3 insertions, 11 deletions

diff --git a/flang/lib/Semantics/resolve-names-utils.cpp b/flang/lib/Semantics/resolve-names-utils.cpp
index 5564570..d6f0302 100644
--- a/flang/lib/Semantics/resolve-names-utils.cpp
+++ b/flang/lib/Semantics/resolve-names-utils.cpp
@@ -365,7 +365,8 @@ void EquivalenceSets::AddToSet(const parser::Designator &designator) {
       }
     }
     auto substringStart{currObject_.substringStart};
-    currSet_.emplace_back(symbol, subscripts, substringStart);
+    currSet_.emplace_back(
+        symbol, subscripts, substringStart, designator.source);
     PropagateSaveAttr(currSet_.back(), currSet_);
   }
   currObject_ = {};
@@ -446,16 +447,7 @@ void EquivalenceSets::MergeInto(const parser::CharBlock &source,
   EquivalenceSet &dst{sets_[dstIndex]};
   PropagateSaveAttr(dst, src);
   for (const auto &obj : src) {
-    if (const auto *obj2{Find(dst, obj.symbol)}) {
-      if (obj == *obj2) {
-        continue; // already there
-      }
-      context_.Say(source,
-          "'%s' and '%s' cannot have the same first storage unit"_err_en_US,
-          obj2->AsFortran(), obj.AsFortran());
-    } else {
-      dst.push_back(obj);
-    }
+    dst.push_back(obj);
     objectToSet_[obj] = dstIndex;
   }
   PropagateSaveAttr(src, dst);