[ClangImporter] Simplify inferDefaultArgument by removing numParams (#27864)

The only thing this was used for is to test if the total number of
parameters was 1, in which case we did the same thing we did for a
first parameter except in one very contrived case: a method with more
than one parameter whose base name starts with "set" and whose first
parameter is an NSZone. There are zero of these in the macOS or iOS
SDKs, and probably even fewer in third-party code.

Author: jrose-apple

lib/ClangImporter/ImportName.cpp

@@ -841,8 +841,8 @@ static bool omitNeedlessWordsInFunctionName(
             param->getType(),
             getParamOptionality(swiftLanguageVersion, param,
                                 !nonNullArgs.empty() && nonNullArgs[i]),
-            nameImporter.getIdentifier(baseName), numParams, argumentName,
-            i == 0, isLastParameter, nameImporter) != DefaultArgumentKind::None;
+            nameImporter.getIdentifier(baseName), argumentName, i == 0,
+            isLastParameter, nameImporter) != DefaultArgumentKind::None;
 
     paramTypes.push_back(getClangTypeNameForOmission(clangCtx,
                                                      param->getOriginalType())

lib/ClangImporter/ImportType.cpp

@@ -1762,13 +1762,12 @@ static bool isObjCMethodResultAudited(const clang::Decl *decl) {
 
 DefaultArgumentKind ClangImporter::Implementation::inferDefaultArgument(
     clang::QualType type, OptionalTypeKind clangOptionality,
-    DeclBaseName baseName, unsigned numParams, StringRef argumentLabel,
-    bool isFirstParameter, bool isLastParameter, NameImporter &nameImporter) {
+    DeclBaseName baseName, StringRef argumentLabel, bool isFirstParameter,
+    bool isLastParameter, NameImporter &nameImporter) {
   auto baseNameStr = baseName.userFacingName();
 
-  // Don't introduce a default argument for setters with only a single
-  // parameter.
-  if (numParams == 1 && camel_case::getFirstWord(baseNameStr) == "set")
+  // Don't introduce a default argument for the first parameter of setters.
+  if (isFirstParameter && camel_case::getFirstWord(baseNameStr) == "set")
     return DefaultArgumentKind::None;
 
   // Some nullable parameters default to 'nil'.
@@ -1789,10 +1788,6 @@ DefaultArgumentKind ClangImporter::Implementation::inferDefaultArgument(
     }
   }
 
-  // Don't introduce an empty options default arguments for setters.
-  if (isFirstParameter && camel_case::getFirstWord(baseNameStr) == "set")
-    return DefaultArgumentKind::None;
-
   // Option sets default to "[]" if they have "Options" in their name.
   if (const clang::EnumType *enumTy = type->getAs<clang::EnumType>()) {
     const clang::EnumDecl *enumDef = enumTy->getDecl()->getDefinition();
@@ -2175,8 +2170,7 @@ ImportedType ClangImporter::Implementation::importMethodParamsAndReturnType(
 
       auto defaultArg = inferDefaultArgument(
           param->getType(), optionalityOfParam,
-          importedName.getDeclName().getBaseName(), numEffectiveParams,
-          name.empty() ? StringRef() : name.str(), paramIndex == 0,
+          importedName.getDeclName().getBaseName(), name.str(), paramIndex == 0,
           isLastParameter, getNameImporter());
       if (defaultArg != DefaultArgumentKind::None)
         paramInfo->setDefaultArgumentKind(defaultArg);

lib/ClangImporter/ImporterImpl.h

@@ -1070,9 +1070,9 @@ class LLVM_LIBRARY_VISIBILITY ClangImporter::Implementation
   /// given Clang \c type, \c baseName, and optionality.
   static DefaultArgumentKind
   inferDefaultArgument(clang::QualType type, OptionalTypeKind clangOptionality,
-                       DeclBaseName baseName, unsigned numParams,
-                       StringRef argumentLabel, bool isFirstParameter,
-                       bool isLastParameter, importer::NameImporter &);
+                       DeclBaseName baseName, StringRef argumentLabel,
+                       bool isFirstParameter, bool isLastParameter,
+                       importer::NameImporter &nameImporter);
 
   /// Import the parameter and return types of an Objective-C method.
   ///