[WIP] Disallow macro default argument with argument

Need to use variable from caller side context

Author: ApolloZhu

include/swift/AST/DiagnosticsSema.def

@@ -7523,11 +7523,15 @@ ERROR(extension_macro_invalid_conformance,none,
 ERROR(macro_attached_to_invalid_decl,none,
       "'%0' macro cannot be attached to %1 (%base2)",
       (StringRef, DescriptiveDeclKind, const Decl *))
+ERROR(conformance_macro,none,
+      "conformance macros are replaced by extension macros",
+      ())
+
 ERROR(macro_as_default_argument, none,
       "non-built-in macro cannot be used as default argument",
       ())
-ERROR(conformance_macro,none,
-      "conformance macros are replaced by extension macros",
+ERROR(macro_as_default_argument_has_arguments, none,
+      "macro used as default argument cannot have arguments",
       ())
 
 ERROR(macro_resolve_circular_reference, none,

include/swift/Basic/MacroRoles.def

@@ -70,9 +70,6 @@ ATTACHED_MACRO_ROLE(Conformance, "conformance", "c")
 /// declarations in a code block.
 EXPERIMENTAL_FREESTANDING_MACRO_ROLE(CodeItem, "codeItem", CodeItemMacros)
 
-/// A freestanding macro that is used as the default argument
-EXPERIMENTAL_FREESTANDING_MACRO_ROLE(DefaultArgument, "defaultArgument", ExpressionMacroDefaultArguments)
-
 /// An attached macro that adds extensions to the declaration the
 /// macro is attached to.
 ATTACHED_MACRO_ROLE(Extension, "extension", "e")

lib/AST/ASTMangler.cpp

@@ -3877,7 +3877,6 @@ void ASTMangler::appendMacroExpansionContext(
 
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::ReplacedFunctionBody:
-  // TODO: ApolloZhu check if this correct?
   case GeneratedSourceInfo::DefaultArgument:
     return appendContext(origDC, StringRef());
   }
@@ -3929,6 +3928,7 @@ void ASTMangler::appendMacroExpansionContext(
 
   case GeneratedSourceInfo::PrettyPrinted:
   case GeneratedSourceInfo::ReplacedFunctionBody:
+  case GeneratedSourceInfo::DefaultArgument:
     llvm_unreachable("Exited above");
   }
 

lib/AST/Module.cpp

@@ -920,6 +920,8 @@ ModuleDecl::getOriginalLocation(SourceLoc loc) const {
       bufferID = SM.findBufferContainingLoc(loc);
       break;
     }
+    case GeneratedSourceInfo::DefaultArgument:
+      // TODO: ApolloZhu
     case GeneratedSourceInfo::ReplacedFunctionBody:
       // There's not really any "original" location for locations within
       // replaced function bodies. The body is actually different code to the

lib/AST/TypeCheckRequests.cpp

@@ -2123,6 +2123,7 @@ UniqueUnderlyingTypeSubstitutionsRequest::evaluate(
       switch (sf->Kind) {
       case SourceFileKind::Interface:
       case SourceFileKind::MacroExpansion:
+      case SourceFileKind::DefaultArgument:
       case SourceFileKind::SIL:
         return true;
       case SourceFileKind::Main:

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1133,12 +1133,18 @@ Expr *DefaultArgumentExprRequest::evaluate(Evaluator &evaluator,
   assert(initExpr);
 
   // Prohibit default argument that is a non-built-in macro to avoid confusion,
-  // unless the experimental feature flag is set.
-  auto isMacroExpansionExpr = isa<MacroExpansionExpr>(initExpr);
-  if (isMacroExpansionExpr &&
-      !ctx.LangOpts.hasFeature(Feature::ExpressionMacroDefaultArguments)) {
-    ctx.Diags.diagnose(initExpr->getLoc(), diag::macro_as_default_argument);
-    return new (ctx) ErrorExpr(initExpr->getSourceRange(), ErrorType::get(ctx));
+  auto macroExpansionExpr = dyn_cast<MacroExpansionExpr>(initExpr);
+  if (macroExpansionExpr) {
+    // unless the experimental feature flag is set.
+    if (!ctx.LangOpts.hasFeature(Feature::ExpressionMacroDefaultArguments)) {
+      ctx.Diags.diagnose(initExpr->getLoc(), diag::macro_as_default_argument);
+      return new (ctx) ErrorExpr(initExpr->getSourceRange(), ErrorType::get(ctx));
+    }
+    auto args = macroExpansionExpr->getArgs();
+    if (!args->empty()) {
+      ctx.Diags.diagnose(args->getLoc(), diag::macro_as_default_argument_has_arguments);
+      return new (ctx) ErrorExpr(initExpr->getSourceRange(), ErrorType::get(ctx));
+    }
   }
 
   // If the param has an error type, there's no point type checking the default
@@ -1157,7 +1163,7 @@ Expr *DefaultArgumentExprRequest::evaluate(Evaluator &evaluator,
   }
 
   // Expression macro default arguments are checked at caller side
-  if (isMacroExpansionExpr)
+  if (macroExpansionExpr)
     return initExpr;
 
   // Walk the checked initializer and contextualize any closures

lib/Sema/TypeCheckExpr.cpp

@@ -774,8 +774,6 @@ static Expr *synthesizeCallerSideDefault(const ParamDecl *param,
 #include "swift/AST/MagicIdentifierKinds.def"
 
   case DefaultArgumentKind::ExpressionMacro: {
-    // FIXME: ApolloZhu what is macro has parameters that references
-    // other things in decl context?
     SmallString<128> scratch;
     const StringRef text = param->getDefaultValueStringRepresentation(scratch);
     SourceFile *defaultArgSourceFile =

lib/Sema/TypeCheckStmt.cpp

@@ -2819,6 +2819,7 @@ static bool requiresDefinition(Decl *decl) {
     case SourceFileKind::Library:
     case SourceFileKind::Main:
     case SourceFileKind::MacroExpansion:
+    case SourceFileKind::DefaultArgument:
       break;
     }
   }

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -2043,37 +2043,14 @@ public struct ClosureCallerMacro: ExpressionMacro {
     }
 }
 
-public struct PrependHelloMacro: ExpressionMacro {
+public struct PrependHelloToShadowedMacro: ExpressionMacro {
     public static func expansion(
       of node: some FreestandingMacroExpansionSyntax,
       in context: some MacroExpansionContext
     ) -> ExprSyntax {
-        """
-        "hello " + \(node.arguments.first!.expression)
-        """
-    }
-}
-
-public struct AsIsMacro: ExpressionMacro {
-    public static func expansion(
-      of node: some FreestandingMacroExpansionSyntax,
-      in context: some MacroExpansionContext
-    ) -> ExprSyntax {
-        node.arguments.first!.expression
-    }
-}
-
-public struct IntroduceShadowedMacro: ExpressionMacro {
-    public static func expansion(
-      of node: some FreestandingMacroExpansionSyntax,
-      in context: some MacroExpansionContext
-    ) -> ExprSyntax {
-        """
-        {
-            let shadowed = "from shadow"
-            return \(node.arguments.first!.expression)
-        }()
-        """
+        #"""
+        "hello \(shadowed)"
+        """#
     }
 }
 

test/Macros/Inputs/with_macro_default_arg_interface.swift

@@ -4,18 +4,8 @@ public macro FileID<T: ExpressibleByStringLiteral>() -> T = #externalMacro(
 )
 
 @freestanding(expression)
-public macro PrependHello(_ param: String) -> String = #externalMacro(
-    module: "MacroDefinition", type: "PrependHelloMacro"
-)
-
-@freestanding(expression)
-public macro AsIs<T>(_ param: T) -> T = #externalMacro(
-    module: "MacroDefinition", type: "AsIsMacro"
-)
-
-@freestanding(expression)
-public macro IntroduceShadowed<T>(_ param: T) -> T = #externalMacro(
-    module: "MacroDefinition", type: "IntroduceShadowedMacro"
+public macro PrependHelloToShadowed() -> String = #externalMacro(
+    module: "MacroDefinition", type: "PrependHelloToShadowedMacro"
 )
 
 @freestanding(expression)
@@ -43,26 +33,8 @@ public struct ClosureCaller {
 
 public let shadowed = "world"
 
-public func testParameterUseVariableFromOriginalDeclContext(
-    param: String = #PrependHello(shadowed)
-) {
-    print(param)
-}
-
-public func testMacroUseMacro(
-    param: String = #PrependHello(#fileID)
-) {
-    print(param)
-}
-
-public func testUseShadowedFromOuterExpansion(
-    param: String = #IntroduceShadowed(#PrependHello(shadowed))
-) {
-    print(param)
-}
-
-public func testNestedStillInOriginalDeclContext(
-    param: String = #AsIs(#PrependHello(shadowed))
+public func preferVariableFromLocalScope(
+    param: String = #PrependHelloToShadowed
 ) {
     print(param)
 }