[interop][SwiftToCxx] NFC, make 'noexcept' a function signature modifier

Author: hyp

lib/PrintAsClang/DeclAndTypePrinter.cpp

@@ -1413,16 +1413,15 @@ class DeclAndTypePrinter::Implementation
         owningPrinter.interopContext, owningPrinter);
     DeclAndTypeClangFunctionPrinter::FunctionSignatureModifiers modifiers;
     modifiers.isInline = true;
+    // FIXME: Support throwing exceptions for Swift errors.
+    modifiers.isNoexcept = !funcTy->isThrowing();
     auto result = funcPrinter.printFunctionSignature(
         FD, funcABI.getSignature(), cxx_translation::getNameForCxx(FD),
         resultTy,
         DeclAndTypeClangFunctionPrinter::FunctionSignatureKind::CxxInlineThunk,
         modifiers);
     assert(
         !result.isUnsupported()); // The C signature should be unsupported too.
-    // FIXME: Support throwing exceptions for Swift errors.
-    if (!funcTy->isThrowing())
-      os << " noexcept";
     printFunctionClangAttributes(FD, funcTy);
     printAvailability(FD);
     os << " {\n";

lib/PrintAsClang/PrintClangFunction.cpp

@@ -903,6 +903,8 @@ ClangRepresentation DeclAndTypeClangFunctionPrinter::printFunctionSignature(
   os << ')';
   if (modifiers.isConst)
     os << " const";
+  if (modifiers.isNoexcept)
+    os << " noexcept";
   return resultingRepresentation;
 }
 

lib/PrintAsClang/PrintClangFunction.h

@@ -86,6 +86,7 @@ class DeclAndTypeClangFunctionPrinter {
     bool isStatic = false;
     bool isInline = false;
     bool isConst = false;
+    bool isNoexcept = false;
 
     FunctionSignatureModifiers() {}
   };