Remove findMacroForCustomAttr in favor of namelookup::lookupMacros

The former was effectively a copy of the latter.

Author: DougGregor

include/swift/AST/MacroDeclaration.h

@@ -116,12 +116,6 @@ StringRef getMacroIntroducedDeclNameString(
 
 class CustomAttr;
 
-/// Perform lookup to determine whether the given custom attribute refers to
-/// a macro declaration, and populate the \c macros vector with the lookup
-/// results that are attached macros.
-void findMacroForCustomAttr(CustomAttr *attr, DeclContext *dc,
-                            llvm::TinyPtrVector<ValueDecl *> &macros);
-
 class MacroIntroducedDeclName {
 public:
   using Kind = MacroIntroducedDeclNameKind;

lib/AST/NameLookup.cpp

@@ -3474,40 +3474,19 @@ GenericParamListRequest::evaluate(Evaluator &evaluator, GenericContext *value) c
       parsedGenericParams->getRAngleLoc());
 }
 
-void swift::findMacroForCustomAttr(CustomAttr *attr, DeclContext *dc,
-                                   llvm::TinyPtrVector<ValueDecl *> &macros) {
-  auto *identTypeRepr = dyn_cast_or_null<IdentTypeRepr>(attr->getTypeRepr());
-  if (!identTypeRepr)
-    return;
-
-  // Look for macros at module scope. They can only occur at module scope, and
-  // we need to be sure not to trigger name lookup into type contexts along
-  // the way.
-  auto moduleScopeDC = dc->getModuleScopeContext();
-  ASTContext &ctx = moduleScopeDC->getASTContext();
-  UnqualifiedLookupDescriptor descriptor(
-      identTypeRepr->getNameRef(), moduleScopeDC
-  );
-  auto lookup = evaluateOrDefault(
-      ctx.evaluator, UnqualifiedLookupRequest{descriptor}, {});
-  for (const auto &result : lookup.allResults()) {
-    // Only keep attached macros, which can be spelled as custom attributes.
-    if (auto macro = dyn_cast<MacroDecl>(result.getValueDecl()))
-      if (isAttachedMacro(macro->getMacroRoles()))
-        macros.push_back(macro);
-  }
-}
-
 NominalTypeDecl *
 CustomAttrNominalRequest::evaluate(Evaluator &evaluator,
                                    CustomAttr *attr, DeclContext *dc) const {
   // Look for names at module scope, so we don't trigger name lookup for
   // nested scopes. At this point, we're looking to see whether there are
   // any suitable macros.
-  llvm::TinyPtrVector<ValueDecl *> macros;
-  findMacroForCustomAttr(attr, dc, macros);
-  if (!macros.empty())
-    return nullptr;
+  if (auto *identTypeRepr =
+          dyn_cast_or_null<IdentTypeRepr>(attr->getTypeRepr())) {
+    auto macros = namelookup::lookupMacros(
+        dc, identTypeRepr->getNameRef(), getAttachedMacroRoles());
+    if (!macros.empty())
+      return nullptr;
+  }
 
   // Find the types referenced by the custom attribute.
   auto &ctx = dc->getASTContext();