[Macros] Always exclude macro expansions in TypeChecker::lookupMacros.

Author: hborla

lib/Sema/CSGen.cpp

@@ -1244,7 +1244,7 @@ namespace {
 
         auto macroIdent = ctx.getIdentifier(kind);
         auto macros = lookupMacros(
-            macroIdent, expr->getLoc(), FunctionRefKind::Unapplied,
+            macroIdent, FunctionRefKind::Unapplied,
             MacroRole::Expression);
         if (!macros.empty()) {
           // Introduce an overload set for the macro reference.
@@ -3896,12 +3896,12 @@ namespace {
 
     /// Lookup all macros with the given macro name.
     SmallVector<OverloadChoice, 1>
-    lookupMacros(Identifier macroName, SourceLoc loc,
+    lookupMacros(Identifier macroName,
                  FunctionRefKind functionRefKind,
                  MacroRoles roles) {
       SmallVector<OverloadChoice, 1> choices;
       auto results = TypeChecker::lookupMacros(
-          CurDC, DeclNameRef(macroName), loc, roles);
+          CurDC, DeclNameRef(macroName), roles);
       for (const auto &result : results) {
         OverloadChoice choice = OverloadChoice(Type(), result, functionRefKind);
         choices.push_back(choice);
@@ -3926,8 +3926,7 @@ namespace {
       auto macroIdent = expr->getMacroName().getBaseIdentifier();
       FunctionRefKind functionRefKind = FunctionRefKind::SingleApply;
       auto macros = lookupMacros(
-          macroIdent, expr->getMacroNameLoc().getBaseNameLoc(),
-          functionRefKind, expr->getMacroRoles());
+          macroIdent, functionRefKind, expr->getMacroRoles());
       if (macros.empty()) {
         ctx.Diags.diagnose(expr->getMacroNameLoc(), diag::macro_undefined,
                            macroIdent)

lib/Sema/TypeCheckDecl.cpp

@@ -1611,11 +1611,19 @@ TypeChecker::lookupPrecedenceGroup(DeclContext *dc, Identifier name,
 
 SmallVector<MacroDecl *, 1>
 TypeChecker::lookupMacros(DeclContext *dc, DeclNameRef macroName,
-                          SourceLoc loc, MacroRoles roles) {
+                          MacroRoles roles) {
   SmallVector<MacroDecl *, 1> choices;
   auto moduleScopeDC = dc->getModuleScopeContext();
   ASTContext &ctx = moduleScopeDC->getASTContext();
-  UnqualifiedLookupDescriptor descriptor(macroName, moduleScopeDC);
+
+  // Macro lookup should always exclude macro expansions; macro
+  // expansions cannot introduce new macro declarations. Note that
+  // the source location here doesn't matter.
+  UnqualifiedLookupDescriptor descriptor{
+    macroName, moduleScopeDC, SourceLoc(),
+    UnqualifiedLookupFlags::ExcludeMacroExpansions
+  };
+
   auto lookup = evaluateOrDefault(
       ctx.evaluator, UnqualifiedLookupRequest{descriptor}, {});
   for (const auto &found : lookup.allResults()) {

lib/Sema/TypeCheckMacros.cpp

@@ -1487,7 +1487,7 @@ ConcreteDeclRef ResolveMacroRequest::evaluate(Evaluator &evaluator,
   // So bail out to prevent diagnostics from the contraint system.
   if (macroRef.getAttr()) {
     auto foundMacros = TypeChecker::lookupMacros(
-        dc, macroRef.getMacroName(), SourceLoc(), roles);
+        dc, macroRef.getMacroName(), roles);
     if (foundMacros.empty())
       return ConcreteDeclRef();
   }

lib/Sema/TypeChecker.h

@@ -940,8 +940,7 @@ PrecedenceGroupLookupResult
 lookupPrecedenceGroup(DeclContext *dc, Identifier name, SourceLoc nameLoc);
 
 SmallVector<MacroDecl *, 1>
-lookupMacros(DeclContext *dc, DeclNameRef macroName, SourceLoc loc,
-             MacroRoles contexts);
+lookupMacros(DeclContext *dc, DeclNameRef macroName, MacroRoles contexts);
 
 enum class UnsupportedMemberTypeAccessKind : uint8_t {
   None,