[flang] Complete RESULT() name constraint checking

flang/lib/Semantics/check-declarations.cpp

@@ -1352,7 +1352,7 @@ void CheckHelper::CheckSubprogram(
     SubprogramMatchHelper{*this}.Check(symbol, *iface);
   }
   if (const Scope *entryScope{details.entryScope()}) {
-    // ENTRY 15.6.2.6, esp. C1571
+    // ENTRY F'2023 15.6.2.6
     std::optional<parser::MessageFixedText> error;
     const Symbol *subprogram{entryScope->symbol()};
     const SubprogramDetails *subprogramDetails{nullptr};
@@ -1384,6 +1384,27 @@ void CheckHelper::CheckSubprogram(
       }
     }
   }
+  if (details.isFunction() &&
+      details.result().name() != symbol.name()) { // F'2023 C1569 & C1583
+    if (auto iter{symbol.owner().find(details.result().name())};
+        iter != symbol.owner().end()) {
+      const Symbol &resNameSym{*iter->second};
+      if (const auto *resNameSubp{resNameSym.detailsIf<SubprogramDetails>()}) {
+        if (const Scope * resNameEntryScope{resNameSubp->entryScope()}) {
+          const Scope *myScope{
+              details.entryScope() ? details.entryScope() : symbol.scope()};
+          if (resNameEntryScope == myScope) {
+            if (auto *msg{messages_.Say(symbol.name(),
+                    "Explicit RESULT('%s') of function '%s' cannot have the same name as a distinct ENTRY into the same scope"_err_en_US,
+                    details.result().name(), symbol.name())}) {
+              msg->Attach(
+                  resNameSym.name(), "ENTRY with conflicting name"_en_US);
+            }
+          }
+        }
+      }
+    }
+  }
   if (const MaybeExpr & stmtFunction{details.stmtFunction()}) {
     if (auto msg{evaluate::CheckStatementFunction(
             symbol, *stmtFunction, context_.foldingContext())}) {

flang/lib/Semantics/resolve-names.cpp

@@ -4048,27 +4048,10 @@ void SubprogramVisitor::CreateEntry(
       attrs = extant->attrs();
     }
   }
-  bool badResultName{false};
   std::optional<SourceName> distinctResultName;
   if (suffix && suffix->resultName &&
       suffix->resultName->source != entryName.source) {
     distinctResultName = suffix->resultName->source;
-    const parser::Name &resultName{*suffix->resultName};
-    if (resultName.source == subprogram.name()) { // C1574
-      Say2(resultName.source,
-          "RESULT(%s) may not have the same name as the function"_err_en_US,
-          subprogram, "Containing function"_en_US);
-      badResultName = true;
-    } else if (const Symbol * extant{FindSymbol(outer, resultName)}) { // C1574
-      if (const auto *details{extant->detailsIf<SubprogramDetails>()}) {
-        if (details->entryScope() == &currScope()) {
-          Say2(resultName.source,
-              "RESULT(%s) may not have the same name as an ENTRY in the function"_err_en_US,
-              extant->name(), "Conflicting ENTRY"_en_US);
-          badResultName = true;
-        }
-      }
-    }
   }
   if (outer.IsModule() && !attrs.test(Attr::PRIVATE)) {
     attrs.set(Attr::PUBLIC);
@@ -4104,17 +4087,24 @@ void SubprogramVisitor::CreateEntry(
     EntityDetails resultDetails;
     resultDetails.set_funcResult(true);
     if (distinctResultName) {
-      if (!badResultName) {
-        // RESULT(x) can be the same explicitly-named RESULT(x) as
-        // the enclosing function or another ENTRY.
-        if (auto iter{currScope().find(suffix->resultName->source)};
-            iter != currScope().end()) {
-          result = &*iter->second;
-        }
-        if (!result) {
-          result = &MakeSymbol(
-              *distinctResultName, Attrs{}, std::move(resultDetails));
-        }
+      // An explicit RESULT() can also be an explicit RESULT()
+      // of the function or another ENTRY.
+      if (auto iter{currScope().find(suffix->resultName->source)};
+          iter != currScope().end()) {
+        result = &*iter->second;
+      }
+      if (!result) {
+        result =
+            &MakeSymbol(*distinctResultName, Attrs{}, std::move(resultDetails));
+      } else if (!result->has<EntityDetails>()) {
+        Say(*distinctResultName,
+            "ENTRY cannot have RESULT(%s) that is not a variable"_err_en_US,
+            *distinctResultName)
+            .Attach(result->name(), "Existing declaration of '%s'"_en_US,
+                result->name());
+        result = nullptr;
+      }
+      if (result) {
         Resolve(*suffix->resultName, *result);
       }
     } else {
@@ -4124,8 +4114,7 @@ void SubprogramVisitor::CreateEntry(
       entryDetails.set_result(*result);
     }
   }
-  if (subpFlag == Symbol::Flag::Subroutine ||
-      (distinctResultName && !badResultName)) {
+  if (subpFlag == Symbol::Flag::Subroutine || distinctResultName) {
     Symbol &assoc{MakeSymbol(entryName.source)};
     assoc.set_details(HostAssocDetails{*entrySymbol});
     assoc.set(Symbol::Flag::Subroutine);

flang/test/Semantics/entry01.f90

@@ -86,11 +86,12 @@ function ifunc()
   entry ibad2()
   !ERROR: ENTRY in a function may not have an alternate return dummy argument
   entry ibadalt(*) ! C1573
-  !ERROR: RESULT(ifunc) may not have the same name as the function
+  !ERROR: ENTRY cannot have RESULT(ifunc) that is not a variable
   entry isameres() result(ifunc) ! C1574
   entry iok()
-  !ERROR: RESULT(iok) may not have the same name as an ENTRY in the function
+  !ERROR: Explicit RESULT('iok') of function 'isameres2' cannot have the same name as a distinct ENTRY into the same scope
   entry isameres2() result(iok) ! C1574
+  !ERROR: Explicit RESULT('iok2') of function 'isameres3' cannot have the same name as a distinct ENTRY into the same scope
   entry isameres3() result(iok2) ! C1574
   !ERROR: 'iok2' is already declared in this scoping unit
   entry iok2()
@@ -255,3 +256,13 @@ subroutine s7(q,q)
   !ERROR: 'z' appears more than once as a dummy argument name in this ENTRY statement
   entry baz(z,z)
 end
+
+!ERROR: Explicit RESULT('f8e1') of function 'f8' cannot have the same name as a distinct ENTRY into the same scope
+function f8() result(f8e1)
+  entry f8e1()
+  entry f8e2() result(f8e2) ! ok
+  !ERROR: Explicit RESULT('f8e1') of function 'f8e3' cannot have the same name as a distinct ENTRY into the same scope
+  entry f8e3() result(f8e1)
+  !ERROR: ENTRY cannot have RESULT(f8) that is not a variable
+  entry f8e4() result(f8)
+end