[Macros] Diagnose macros attached to declarations they cannot apply to.

Author: hborla

include/swift/AST/DiagnosticsSema.def

@@ -7268,6 +7268,9 @@ ERROR(local_extension_macro,none,
 ERROR(extension_macro_invalid_conformance,none,
       "invalid protocol conformance %0 in extension macro",
       (Type))
+ERROR(macro_attached_to_invalid_decl,none,
+      "'%0' macro cannot be attached to %1",
+      (StringRef, DescriptiveDeclKind))
 
 ERROR(macro_resolve_circular_reference, none,
       "circular reference resolving %select{freestanding|attached}0 macro %1",

lib/Sema/TypeCheckAttr.cpp

@@ -3665,10 +3665,17 @@ void AttributeChecker::visitCustomAttr(CustomAttr *attr) {
     Ctx.evaluator, CustomAttrNominalRequest{attr, dc}, nullptr);
 
   if (!nominal) {
+    if (attr->isInvalid())
+      return;
+
     // Try resolving an attached macro attribute.
-    auto *macro = D->getResolvedMacro(attr);
-    if (macro || !attr->isValid())
+    if (auto *macro = D->getResolvedMacro(attr)) {
+      for (auto *roleAttr : macro->getAttrs().getAttributes<MacroRoleAttr>()) {
+        diagnoseInvalidAttachedMacro(roleAttr->getMacroRole(), D);
+      }
+
       return;
+    }
 
     // Diagnose errors.
 

lib/Sema/TypeCheckMacros.cpp

@@ -543,6 +543,51 @@ static Identifier makeIdentifier(ASTContext &ctx, std::nullptr_t) {
   return Identifier();
 }
 
+bool swift::diagnoseInvalidAttachedMacro(MacroRole role,
+                                         Decl *attachedTo) {
+  switch (role) {
+  case MacroRole::Expression:
+  case MacroRole::Declaration:
+  case MacroRole::CodeItem:
+    llvm_unreachable("Invalid macro role for attached macro");
+
+  case MacroRole::Accessor:
+    // Only var decls and subscripts have accessors.
+    if (isa<AbstractStorageDecl>(attachedTo) && !isa<ParamDecl>(attachedTo))
+      return false;
+
+    break;
+
+  case MacroRole::MemberAttribute:
+  case MacroRole::Member:
+    // Nominal types and extensions can have members.
+    if (isa<NominalTypeDecl>(attachedTo) || isa<ExtensionDecl>(attachedTo))
+      return false;
+
+    break;
+
+  case MacroRole::Peer:
+    // Peer macros are allowed on everything except parameters.
+    if (!isa<ParamDecl>(attachedTo))
+      return false;
+
+    break;
+
+  case MacroRole::Conformance:
+  case MacroRole::Extension:
+    // Only primary declarations of nominal types
+    if (isa<NominalTypeDecl>(attachedTo))
+      return false;
+
+    break;
+  }
+
+  attachedTo->diagnose(diag::macro_attached_to_invalid_decl,
+                       getMacroRoleString(role),
+                       attachedTo->getDescriptiveKind());
+  return true;
+}
+
 static void diagnoseInvalidDecl(Decl *decl,
                                 MacroDecl *macro,
                                 llvm::function_ref<bool(DeclName)> coversName) {

lib/Sema/TypeCheckMacros.h

@@ -90,6 +90,11 @@ bool accessorMacroOnlyIntroducesObservers(
 bool accessorMacroIntroducesInitAccessor(
     MacroDecl *macro, const MacroRoleAttr *attr);
 
+/// Diagnose an error if the given macro role does not apply
+/// to the declaration kind of \c attachedTo.
+bool diagnoseInvalidAttachedMacro(MacroRole role,
+                                  Decl *attachedTo);
+
 } // end namespace swift
 
 #endif /* SWIFT_SEMA_TYPECHECKMACROS_H */

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -1314,6 +1314,16 @@ public struct EmptyMacro: MemberMacro {
   }
 }
 
+public struct EmptyPeerMacro: PeerMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    providingPeersOf declaration: some DeclSyntaxProtocol,
+    in context: some MacroExpansionContext
+  ) throws -> [DeclSyntax] {
+    return []
+  }
+}
+
 public struct EquatableMacro: ConformanceMacro {
   public static func expansion(
     of node: AttributeSyntax,

test/Macros/accessor_macros.swift

@@ -112,4 +112,7 @@ struct MyBrokenStruct {
   }
 }
 
+@myPropertyWrapper
+struct CannotHaveAccessors {}
+// CHECK-DIAGS: 'accessor' macro cannot be attached to struct
 #endif

test/Macros/attached_macros_diags.swift

@@ -1,23 +1,20 @@
 // REQUIRES: swift_swift_parser
 
-// RUN: %target-typecheck-verify-swift -swift-version 5 -module-name MacrosTest
+// RUN: %empty-directory(%t)
+// RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -parse-as-library -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
+// RUN: %target-typecheck-verify-swift -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) -disable-availability-checking -module-name MacrosTest
 
-@attached(accessor) macro m1() = #externalMacro(module: "MyMacros", type: "Macro1")
-// expected-warning@-1{{external macro implementation type 'MyMacros.Macro1' could not be found for macro 'm1()'}}
-// expected-note@-2{{'m1()' declared here}}
+@attached(peer) macro m1() = #externalMacro(module: "MacroDefinition", type: "EmptyPeerMacro")
 
-@attached(accessor) macro m2(_: Int) = #externalMacro(module: "MyMacros", type: "Macro2")
-// expected-warning@-1{{external macro implementation type 'MyMacros.Macro2' could not be found for macro 'm2'}}
-// expected-note@-2{{candidate has partially matching parameter list (Int)}}
-// expected-note@-3{{candidate expects value of type 'Int' for parameter #1 (got 'String')}}
+@attached(peer) macro m2(_: Int) = #externalMacro(module: "MacroDefinition", type: "EmptyPeerMacro")
+// expected-note@-1{{candidate has partially matching parameter list (Int)}}
+// expected-note@-2{{candidate expects value of type 'Int' for parameter #1 (got 'String')}}
 
-@attached(accessor) macro m2(_: Double) = #externalMacro(module: "MyMacros", type: "Macro2")
-// expected-warning@-1{{external macro implementation type 'MyMacros.Macro2' could not be found for macro 'm2'}}
-// expected-note@-2{{candidate has partially matching parameter list (Double)}}
-// expected-note@-3{{candidate expects value of type 'Double' for parameter #1 (got 'String')}}
+@attached(peer) macro m2(_: Double) = #externalMacro(module: "MacroDefinition", type: "EmptyPeerMacro")
+// expected-note@-1{{candidate has partially matching parameter list (Double)}}
+// expected-note@-2{{candidate expects value of type 'Double' for parameter #1 (got 'String')}}
 
-@attached(accessor) macro m3(message: String) = #externalMacro(module: "MyMacros", type: "Macro3")
-// expected-warning@-1{{external macro implementation type 'MyMacros.Macro3' could not be found for macro 'm3(message:)'}}
+@attached(peer) macro m3(message: String) = #externalMacro(module: "MacroDefinition", type: "EmptyPeerMacro")
 
 @freestanding(expression) macro stringify<T>(_ value: T) -> (T, String) = #externalMacro(module: "MyMacros", type: "StringifyMacro")
 // expected-warning@-1{{external macro implementation type 'MyMacros.StringifyMacro' could not be found for macro 'stringify'}}
@@ -38,7 +35,12 @@ struct SkipNestedType {
 
   // We select the macro, not the property wrapper.
   @m1 var x: Int = 0
-  // expected-error@-1{{external macro implementation type 'MyMacros.Macro1' could not be found for macro 'm1()'}}
+  //expected-note@-1{{did you mean 'x'?}}
+
+  func test() {
+    let _: m1<Int> = _x
+    // expected-error@-1{{cannot find '_x' in scope}}
+  }
 }
 
 struct TestMacroArgs {

test/Macros/macro_expand_attributes.swift

@@ -140,3 +140,13 @@ expansionOrder.expandedMember = 27
 
 // CHECK: setting 28
 expansionOrder.originalMember = 28
+
+#if TEST_DIAGNOSTICS
+@wrapAllProperties
+typealias A = Int
+// expected-error@-1{{'memberAttribute' macro cannot be attached to type alias}}
+
+@wrapAllProperties
+func noMembers() {}
+// expected-error@-1{{'memberAttribute' macro cannot be attached to global function}}
+#endif

test/Macros/macro_expand_extensions.swift

@@ -111,6 +111,13 @@ func testLocal() {
   // expected-error@-1{{local type cannot have attached extension macro}}
 }
 
+@DelegatedConformance
+typealias A = Int
+// expected-error@-1 {{'extension' macro cannot be attached to type alias}}
+
+@DelegatedConformance
+extension Int {}
+// expected-error@-1 {{'extension' macro cannot be attached to extension}}
 
 @attached(extension, conformances: P)
 macro UndocumentedNamesInExtension() = #externalMacro(module: "MacroDefinition", type: "DelegatedConformanceViaExtensionMacro")

test/Macros/macro_expand_peers.swift

@@ -214,6 +214,13 @@ func testVarPeer() {
   _ = Date().value
 }
 
+#if TEST_DIAGNOSTICS
+// Macros cannot be attached to function parameters
+
+// expected-error@+1{{'peer' macro cannot be attached to parameter}}
+func test(@declareVarValuePeer x: Int) {}
+#endif
+
 // Stored properties added via peer macros.
 @attached(peer, names: named(_foo))
 macro AddPeerStoredProperty() =

test/Macros/macro_expand_synthesized_members.swift

@@ -19,6 +19,12 @@ macro addMembers() = #externalMacro(module: "MacroDefinition", type: "AddMembers
 )
 macro addMembersQuotedInit() = #externalMacro(module: "MacroDefinition", type: "AddMembers")
 
+#if TEST_DIAGNOSTICS
+@addMembers
+import Swift
+// expected-error@-1 {{'member' macro cannot be attached to import}}
+#endif
+
 @addMembers
 struct S {
   func useSynthesized() {