[flang] Add comments and tests for issue 574 fix

Original-commit: flang-compiler/f18@89337ce
Reviewed-on: flang-compiler/f18#672

flang/lib/semantics/expression.cc

@@ -1885,6 +1885,8 @@ static void FixMisparsedFunctionReference(
       Symbol &symbol{origSymbol->GetUltimate()};
       if (symbol.has<semantics::ObjectEntityDetails>() ||
           symbol.has<semantics::AssocEntityDetails>()) {
+        // Note that expression in AssocEntityDetails cannot be a procedure
+        // pointer as per C1105 so this cannot be a function reference.
         if constexpr (common::HasMember<common::Indirection<parser::Designator>,
                           uType>) {
           CheckFuncRefToArrayElementRefHasSubscripts(context, funcRef);

flang/lib/semantics/resolve-names.cc

@@ -5065,7 +5065,11 @@ void ResolveNamesVisitor::HandleProcedureName(
     if (IsProcedure(*symbol) || symbol->has<DerivedTypeDetails>() ||
         symbol->has<ObjectEntityDetails>() ||
         symbol->has<AssocEntityDetails>()) {
-      // these are all valid as procedure-designators
+      // Symbols with DerivedTypeDetails, ObjectEntityDetails and
+      // AssocEntityDetails are accepted here as procedure-designators because
+      // this means the related FunctionReference are mis-parsed structure
+      // constructors or array references that will be fixed later when
+      // analyzing expressions.
     } else if (symbol->test(Symbol::Flag::Implicit)) {
       Say(name,
           "Use of '%s' as a procedure conflicts with its implicit definition"_err_en_US);

flang/test/semantics/resolve39.f90

@@ -28,3 +28,18 @@ subroutine s2
   associate (a => z'1')
   end associate
 end
+
+subroutine s3
+! Test that associated entities are not preventing to fix
+! mis-parsed function references into array references
+  real :: a(10)
+  associate (b => a(2:10:2))
+    ! Check no complains about "Use of 'b' as a procedure"
+    print *, b(1) ! OK
+  end associate
+  associate (c => a(2:10:2))
+    ! Check the function reference has been fixed to an array reference
+    !ERROR: Reference to array 'c' with empty subscript list
+    print *, c()
+  end associate
+end