[flang][driver] add ability to look up feature flags without setting them (#144559)

This just adds some convenience methods to feature control and rewrites
old code in terms of those methods. Also cleans up some names that I
just realize were overloads of another method.

2 files changed, 13 insertions, 12 deletions

diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 147849b..2603a3f 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -1011,7 +1011,7 @@ static bool parseDiagArgs(CompilerInvocation &res, llvm::opt::ArgList &args,
       if (wArg == "error") {
         res.setWarnAsErr(true);
         // -W(no-)<feature>
-      } else if (!features.ApplyCliOption(wArg)) {
+      } else if (!features.EnableWarning(wArg)) {
         const unsigned diagID = diags.getCustomDiagID(
             clang::DiagnosticsEngine::Error, "Unknown diagnostic option: -W%0");
         diags.Report(diagID) << wArg;
diff --git a/flang/lib/Support/Fortran-features.cpp b/flang/lib/Support/Fortran-features.cpp
index 08ded17..17b5f83 100644
--- a/flang/lib/Support/Fortran-features.cpp
+++ b/flang/lib/Support/Fortran-features.cpp
@@ -151,22 +151,23 @@ LanguageFeatureControl::LanguageFeatureControl() {
   warnLanguage_.set(LanguageFeature::NullActualForAllocatable);
 }
 
-// Take a string from the Cli and apply it to the LanguageFeatureControl.
-bool LanguageFeatureControl::ApplyCliOption(std::string input) {
+std::optional<LanguageControlFlag> LanguageFeatureControl::FindWarning(
+    std::string_view input) {
   bool negated{false};
   if (input.size() > 3 && input.substr(0, 3) == "no-") {
     negated = true;
     input = input.substr(3);
   }
-  if (auto it{cliOptions_.find(input)}; it != cliOptions_.end()) {
-    if (std::holds_alternative<LanguageFeature>(it->second)) {
-      EnableWarning(std::get<LanguageFeature>(it->second), !negated);
-      return true;
-    }
-    if (std::holds_alternative<UsageWarning>(it->second)) {
-      EnableWarning(std::get<UsageWarning>(it->second), !negated);
-      return true;
-    }
+  if (auto it{cliOptions_.find(std::string{input})}; it != cliOptions_.end()) {
+    return std::make_pair(it->second, !negated);
+  }
+  return std::nullopt;
+}
+
+bool LanguageFeatureControl::EnableWarning(std::string_view input) {
+  if (auto warningAndEnabled{FindWarning(input)}) {
+    EnableWarning(warningAndEnabled->first, warningAndEnabled->second);
+    return true;
   }
   return false;
 }