[Mangler] Avoid mangling local discriminator for attached macros

If we're using the macro-specific local discriminator, we need to
make sure we avoid mangling the regular local discriminator in
`appendDeclName`, since that could prematurely kick local discriminator
assignment before type-checking has finished.

rdar://143834482

Author: hamishknight

include/swift/AST/ASTMangler.h

@@ -453,7 +453,8 @@ class ASTMangler : public Mangler {
                   const ValueDecl *forDecl = nullptr);
 
   void appendDeclName(
-      const ValueDecl *decl, DeclBaseName name = DeclBaseName());
+      const ValueDecl *decl, DeclBaseName name = DeclBaseName(),
+      bool skipLocalDiscriminator = false);
 
   GenericTypeParamType *appendAssocType(DependentMemberType *DepTy,
                                         GenericSignature sig,

lib/AST/ASTMangler.cpp

@@ -1199,7 +1199,8 @@ getOverriddenSwiftProtocolObjCName(const ValueDecl *decl,
   return std::nullopt;
 }
 
-void ASTMangler::appendDeclName(const ValueDecl *decl, DeclBaseName name) {
+void ASTMangler::appendDeclName(const ValueDecl *decl, DeclBaseName name,
+                                bool skipLocalDiscriminator) {
   ASSERT(!getABIDecl(decl) && "caller should make sure we get ABI decls");
   if (name.empty())
     name = decl->getBaseName();
@@ -1240,6 +1241,11 @@ void ASTMangler::appendDeclName(const ValueDecl *decl, DeclBaseName name) {
   }
 
   if (decl->getDeclContext()->isLocalContext()) {
+    // If we don't need a local discriminator (attached macros receive a
+    // separate discriminator), we're done.
+    if (skipLocalDiscriminator)
+      return;
+
     if (auto *paramDecl = dyn_cast<ParamDecl>(decl)) {
       if (!decl->hasName()) {
         // Mangle unnamed params with their ordering.
@@ -5158,13 +5164,15 @@ std::string ASTMangler::mangleAttachedMacroExpansion(
 
     // If we needed a local discriminator, stuff that into the name itself.
     // This is hack, but these names aren't stable anyway.
+    bool skipLocalDiscriminator = false;
     if (auto discriminator = precheckedMangleContext.second) {
+      skipLocalDiscriminator = true;
       name = encodeLocalPrecheckedDiscriminator(
           decl->getASTContext(), name, *discriminator);
     }
 
     if (auto valueDecl = dyn_cast<ValueDecl>(decl))
-      appendDeclName(valueDecl, name);
+      appendDeclName(valueDecl, name, skipLocalDiscriminator);
     else if (!name.empty())
       appendIdentifier(name.str());
     else

test/Macros/macro_expand.swift

@@ -142,14 +142,12 @@ func invalidDeclarationMacro() {
 
   @AccidentalCodeItem struct S {}
   // expected-note@-1 {{in expansion of macro 'AccidentalCodeItem' on struct 'S' here}}
-  // CHECK-DIAGS: @__swiftmacro_9MacroUser018invalidDeclarationA0yyF5S_$l0L_18AccidentalCodeItemfMp_.swift:1:1: error: expected macro expansion to produce a declaration
+  // CHECK-DIAGS: @__swiftmacro_9MacroUser018invalidDeclarationA0yyF5S_$l018AccidentalCodeItemfMp_.swift:1:1: error: expected macro expansion to produce a declaration
 
-  struct LocalThing1 {
-    func f() {
-      #accidentalCodeItem
-      // expected-note@-1 {{in expansion of macro 'accidentalCodeItem' here}}
-      // CHECK-DIAGS: @__swiftmacro_9MacroUser018invalidDeclarationA0yyF5S_$l0L_18AccidentalCodeItemfMp_.swift
-    }
+  do {
+    @AccidentalCodeItem struct S {}
+    // expected-note@-1 {{in expansion of macro 'AccidentalCodeItem' on struct 'S' here}}
+    // CHECK-DIAGS: @__swiftmacro_9MacroUser018invalidDeclarationA0yyF5S_$l118AccidentalCodeItemfMp_.swift:1:1: error: expected macro expansion to produce a declaration
   }
 }
 #endif
@@ -648,11 +646,38 @@ struct HasNestedType {
   #DefineComparableType
 }
 
+@attached(accessor)
+macro AddGetter() = #externalMacro(module: "MacroDefinition", type: "AddGetterMacro")
+
+// Make sure the mangling for the accessor macro doesn't kick local
+// discriminator assignment, which would miss the autoclosure.
+func testLocalAccessorMacroWithAutoclosure() {
+  @AddGetter
+  var x: Int = 2
+
+  func takesAutoclosure(_ x: @autoclosure () -> Int) {}
+  takesAutoclosure(1)
+}
+
 #if TEST_DIAGNOSTICS
 @freestanding(expression)
 macro missingMacro() = #externalMacro(module: "MacroDefinition", type: "BluhBlah")
 // FIXME: xpected-warning@-1 {{external macro implementation type 'MacroDefinition.BluhBlah' could not be found for macro 'missingMacro()'; 'MacroDefinition.BluhBlah' could not be found in library plugin '}}
 @freestanding(expression)
 macro notMacro() = #externalMacro(module: "MacroDefinition", type: "NotMacroStruct")
 // FIXME: xpected-warning@-1 {{macro implementation type 'MacroDefinition.NotMacroStruct' could not be found for macro 'notMacro()'; 'MacroDefinition.NotMacroStruct' is not a valid macro implementation type in library plugin '}}
+
+// Because this is a method in a local decl, it ends up getting delayed, so
+// we need to check it at the end of the file.
+// FIXME: We either need to switch to using CHECK-DAG, or ideally teach
+// the diagnostic verifier about macro expansion buffers.
+func invalidDeclarationMacro2() {
+  struct LocalThing1 {
+    func f() {
+      #accidentalCodeItem
+      // expected-note@-1 {{in expansion of macro 'accidentalCodeItem' here}}
+      // CHECK-DIAGS: @__swiftmacro_9MacroUser0023macro_expandswift_elFCffMX[[@LINE-3]]_6_18accidentalCodeItemfMf_.swift:1:1: error: expected macro expansion to produce a declaration
+    }
+  }
+}
 #endif