[flang] Make not yet implemented messages more consistent

To make it easier to find things that are not yet implemented, I'm changing the
messages that appear in the compiler's output to all have the string "not yet
implemented:".

These changes apply to files in the front end.  I have another set of changes
to files in the lowering code.

Differential Revision: https://reviews.llvm.org/D122355

Author: psteinfeld

flang/lib/Semantics/expression.cpp

@@ -1835,7 +1835,7 @@ static std::optional<parser::CharBlock> GetPassName(
 static int GetPassIndex(const Symbol &proc) {
   CHECK(!proc.attrs().test(semantics::Attr::NOPASS));
   std::optional<parser::CharBlock> passName{GetPassName(proc)};
-  const auto *interface{semantics::FindInterface(proc)};
+  const auto *interface { semantics::FindInterface(proc) };
   if (!passName || !interface) {
     return 0; // first argument is passed-object
   }
@@ -3215,26 +3215,28 @@ void ArgumentAnalyzer::Analyze(
   // be detected and represented (they're not expressions).
   // TODO: C1534: Don't allow a "restricted" specific intrinsic to be passed.
   std::optional<ActualArgument> actual;
-  std::visit(common::visitors{
-                 [&](const common::Indirection<parser::Expr> &x) {
-                   actual = AnalyzeExpr(x.value());
-                   SetArgSourceLocation(actual, x.value().source);
-                 },
-                 [&](const parser::AltReturnSpec &label) {
-                   if (!isSubroutine) {
-                     context_.Say(
-                         "alternate return specification may not appear on"
-                         " function reference"_err_en_US);
-                   }
-                   actual = ActualArgument(label.v);
-                 },
-                 [&](const parser::ActualArg::PercentRef &) {
-                   context_.Say("TODO: %REF() argument"_err_en_US);
-                 },
-                 [&](const parser::ActualArg::PercentVal &) {
-                   context_.Say("TODO: %VAL() argument"_err_en_US);
-                 },
-             },
+  std::visit(
+      common::visitors{
+          [&](const common::Indirection<parser::Expr> &x) {
+            actual = AnalyzeExpr(x.value());
+            SetArgSourceLocation(actual, x.value().source);
+          },
+          [&](const parser::AltReturnSpec &label) {
+            if (!isSubroutine) {
+              context_.Say("alternate return specification may not appear on"
+                           " function reference"_err_en_US);
+            }
+            actual = ActualArgument(label.v);
+          },
+          [&](const parser::ActualArg::PercentRef &) {
+            context_.Say(
+                "not yet implemented: %REF() intrinsic for arguments"_err_en_US);
+          },
+          [&](const parser::ActualArg::PercentVal &) {
+            context_.Say(
+                "not yet implemetned: %VAL() intrinsic for arguments"_err_en_US);
+          },
+      },
       std::get<parser::ActualArg>(arg.t).u);
   if (actual) {
     if (const auto &argKW{std::get<std::optional<parser::Keyword>>(arg.t)}) {

flang/lib/Semantics/resolve-names.cpp

@@ -4721,7 +4721,7 @@ bool DeclarationVisitor::Pre(const parser::StructureDef &def) {
 }
 
 bool DeclarationVisitor::Pre(const parser::Union::UnionStmt &) {
-  Say("UNION is not yet supported"_err_en_US); // TODO
+  Say("not yet implemented: support for UNION"_err_en_US); // TODO
   return true;
 }
 

flang/runtime/edit-output.cpp

@@ -411,7 +411,7 @@ bool RealOutputEditing<binaryPrecision>::EditListDirectedOutput(
 template <int binaryPrecision>
 bool RealOutputEditing<binaryPrecision>::EditEXOutput(const DataEdit &) {
   io_.GetIoErrorHandler().Crash(
-      "EX output editing is not yet implemented"); // TODO
+      "not yet implemented: EX output editing"); // TODO
 }
 
 template <int KIND> bool RealOutputEditing<KIND>::Edit(const DataEdit &edit) {

flang/test/Semantics/struct01.f90

@@ -6,7 +6,7 @@ program main
   structure /s/
     !ERROR: /s/ is not a known STRUCTURE
     record /s/ attemptToRecurse
-    !ERROR: UNION is not yet supported
+    !ERROR: not yet implemented: support for UNION
     union
       map
         integer j