swiftlang · CodaFi · Aug 12, 2020 · Aug 11, 2020
diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
@@ -2765,8 +2765,9 @@ ERROR(cannot_synthesize_init_in_extension_of_nonfinal,none,
       "be satisfied by a 'required' initializer in the class definition",
       (Type, DeclName))
 ERROR(cannot_synthesize_in_crossfile_extension,none,
-      "implementation of %0 cannot be automatically synthesized in an extension "
-      "in a different file to the type", (Type))
+      "extension outside of file declaring %0 %1 prevents automatic synthesis "
+      "of %2 for protocol %3",
+      (DescriptiveDeclKind, DeclName, DeclName, Type))
 
 ERROR(broken_additive_arithmetic_requirement,none,
       "AdditiveArithmetic protocol is broken: unexpected requirement", ())

diff --git a/lib/Sema/DerivedConformances.cpp b/lib/Sema/DerivedConformances.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "TypeChecker.h"
+#include "swift/AST/ASTPrinter.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/Stmt.h"
 #include "swift/AST/Expr.h"
@@ -490,8 +491,27 @@ bool DerivedConformance::checkAndDiagnoseDisallowedContext(
       Nominal->getModuleScopeContext() !=
           getConformanceContext()->getModuleScopeContext()) {
     ConformanceDecl->diagnose(diag::cannot_synthesize_in_crossfile_extension,
+                              Nominal->getDescriptiveKind(), Nominal->getName(),
+                              synthesizing->getName(),
                               getProtocolType());
     Nominal->diagnose(diag::kind_declared_here, DescriptiveDeclKind::Type);
+
+    // In editor mode, try to insert a stub.
+    if (Context.LangOpts.DiagnosticsEditorMode) {
+      auto Extension = cast<ExtensionDecl>(getConformanceContext());
+      auto FixitLocation = Extension->getBraces().Start;
+      llvm::SmallString<128> Text;
+      {
+        llvm::raw_svector_ostream SS(Text);
+        swift::printRequirementStub(synthesizing, Nominal,
+                                    Nominal->getDeclaredType(),
+                                    Extension->getStartLoc(), SS);
+        if (!Text.empty()) {
+          ConformanceDecl->diagnose(diag::missing_witnesses_general)
+            .fixItInsertAfter(FixitLocation, Text.str());
+        }
+      }
+    }
     return true;
   }
 

diff --git a/localization/diagnostics/en.yaml b/localization/diagnostics/en.yaml
@@ -6556,8 +6556,8 @@
 
 - id: cannot_synthesize_in_crossfile_extension
   msg: >-
-    implementation of %0 cannot be automatically synthesized in an extension
-    in a different file to the type
+    extension outside of file declaring %0 %1 prevents automatic synthesis
+    of %2 for protocol %3
 
 - id: broken_additive_arithmetic_requirement
   msg: >-

diff --git a/test/AutoDiff/Sema/DerivedConformances/class_differentiable.swift b/test/AutoDiff/Sema/DerivedConformances/class_differentiable.swift
@@ -570,8 +570,10 @@ class WrappedProperties: Differentiable {
 
 // Test derived conformances in disallowed contexts.
 
-// expected-error @+1 2 {{implementation of 'Differentiable' cannot be automatically synthesized in an extension in a different file to the type}}
 extension OtherFileNonconforming: Differentiable {}
+// expected-error @-1 {{extension outside of file declaring class 'OtherFileNonconforming' prevents automatic synthesis of 'move(along:)' for protocol 'Differentiable'}}
+// expected-error @-2 {{extension outside of file declaring class 'OtherFileNonconforming' prevents automatic synthesis of 'zeroTangentVectorInitializer' for protocol 'Differentiable'}}
 
-// expected-error @+1 2 {{implementation of 'Differentiable' cannot be automatically synthesized in an extension in a different file to the type}}
 extension GenericOtherFileNonconforming: Differentiable {}
+// expected-error @-1 {{extension outside of file declaring generic class 'GenericOtherFileNonconforming' prevents automatic synthesis of 'move(along:)' for protocol 'Differentiable'}}
+// expected-error @-2 {{extension outside of file declaring generic class 'GenericOtherFileNonconforming' prevents automatic synthesis of 'zeroTangentVectorInitializer' for protocol 'Differentiable'}}
diff --git a/test/AutoDiff/Sema/DerivedConformances/struct_additive_arithmetic.swift b/test/AutoDiff/Sema/DerivedConformances/struct_additive_arithmetic.swift
@@ -113,8 +113,12 @@ where T: AdditiveArithmetic {}
 
 // Test derived conformances in disallowed contexts.
 
-// expected-error @+1 3 {{implementation of 'AdditiveArithmetic' cannot be automatically synthesized in an extension in a different file to the type}}
 extension OtherFileNonconforming: AdditiveArithmetic {}
+// expected-error @-1 {{extension outside of file declaring struct 'OtherFileNonconforming' prevents automatic synthesis of 'zero' for protocol 'AdditiveArithmetic'}}
+// expected-error @-2 {{extension outside of file declaring struct 'OtherFileNonconforming' prevents automatic synthesis of '+' for protocol 'AdditiveArithmetic'}}
+// expected-error @-3 {{extension outside of file declaring struct 'OtherFileNonconforming' prevents automatic synthesis of '-' for protocol 'AdditiveArithmetic'}}
 
-// expected-error @+1 3 {{implementation of 'AdditiveArithmetic' cannot be automatically synthesized in an extension in a different file to the type}}
 extension GenericOtherFileNonconforming: AdditiveArithmetic {}
+// expected-error @-1 {{extension outside of file declaring generic struct 'GenericOtherFileNonconforming' prevents automatic synthesis of 'zero' for protocol 'AdditiveArithmetic'}}
+// expected-error @-2 {{extension outside of file declaring generic struct 'GenericOtherFileNonconforming' prevents automatic synthesis of '+' for protocol 'AdditiveArithmetic'}}
+// expected-error @-3 {{extension outside of file declaring generic struct 'GenericOtherFileNonconforming' prevents automatic synthesis of '-' for protocol 'AdditiveArithmetic'}}
diff --git a/test/AutoDiff/Sema/DerivedConformances/struct_differentiable.swift b/test/AutoDiff/Sema/DerivedConformances/struct_differentiable.swift
@@ -383,8 +383,10 @@ struct WrappedProperties: Differentiable {
 
 // Verify that cross-file derived conformances are disallowed.
 
-// expected-error @+1 2 {{implementation of 'Differentiable' cannot be automatically synthesized in an extension in a different file to the type}}
 extension OtherFileNonconforming: Differentiable {}
+// expected-error @-1 {{extension outside of file declaring struct 'OtherFileNonconforming' prevents automatic synthesis of 'move(along:)' for protocol 'Differentiable'}}
+// expected-error @-2 {{extension outside of file declaring struct 'OtherFileNonconforming' prevents automatic synthesis of 'zeroTangentVectorInitializer' for protocol 'Differentiable'}}
 
-// expected-error @+1 2 {{implementation of 'Differentiable' cannot be automatically synthesized in an extension in a different file to the type}}
 extension GenericOtherFileNonconforming: Differentiable {}
+// expected-error @-1 {{extension outside of file declaring generic struct 'GenericOtherFileNonconforming' prevents automatic synthesis of 'move(along:)' for protocol 'Differentiable'}}
+// expected-error @-2 {{extension outside of file declaring generic struct 'GenericOtherFileNonconforming' prevents automatic synthesis of 'zeroTangentVectorInitializer' for protocol 'Differentiable'}}
diff --git a/test/Sema/Inputs/fixits-derived-conformances-multifile.swift b/test/Sema/Inputs/fixits-derived-conformances-multifile.swift
@@ -0,0 +1,6 @@
+public enum Enum { case one } // expected-note {{type declared here}}
+public enum GenericEnum<T> { case one(Int) } // expected-note {{type declared here}}
+
+public struct Struct {} // expected-note {{type declared here}}
+public struct GenericStruct<T> {} // expected-note {{type declared here}}
+
diff --git a/test/Sema/enum_conformance_synthesis.swift b/test/Sema/enum_conformance_synthesis.swift
@@ -224,7 +224,7 @@ enum Complex2 {
 }
 extension Complex2 : Hashable {}
 extension Complex2 : CaseIterable {}  // expected-error {{type 'Complex2' does not conform to protocol 'CaseIterable'}}
-extension FromOtherFile: CaseIterable {} // expected-error {{cannot be automatically synthesized in an extension in a different file to the type}}
+extension FromOtherFile: CaseIterable {} // expected-error {{extension outside of file declaring enum 'FromOtherFile' prevents automatic synthesis of 'allCases' for protocol 'CaseIterable'}}
 extension CaseIterableAcrossFiles: CaseIterable {
   public static var allCases: [CaseIterableAcrossFiles] {
     return [ .A ]
@@ -248,7 +248,7 @@ extension OtherFileNonconforming: Hashable {
   func hash(into hasher: inout Hasher) {}
 }
 // ...but synthesis in a type defined in another file doesn't work yet.
-extension YetOtherFileNonconforming: Equatable {} // expected-error {{cannot be automatically synthesized in an extension in a different file to the type}}
+extension YetOtherFileNonconforming: Equatable {} // expected-error {{extension outside of file declaring enum 'YetOtherFileNonconforming' prevents automatic synthesis of '==' for protocol 'Equatable'}}
 extension YetOtherFileNonconforming: CaseIterable {} // expected-error {{does not conform}}
 
 // Verify that an indirect enum doesn't emit any errors as long as its "leaves"
@@ -319,7 +319,7 @@ extension UnusedGenericDeriveExtension: Hashable {}
 // Cross-file synthesis is disallowed for conditional cases just as it is for
 // non-conditional ones.
 extension GenericOtherFileNonconforming: Equatable where T: Equatable {}
-// expected-error@-1{{implementation of 'Equatable' cannot be automatically synthesized in an extension in a different file to the type}}
+// expected-error@-1{{extension outside of file declaring generic enum 'GenericOtherFileNonconforming' prevents automatic synthesis of '==' for protocol 'Equatable'}}
 
 // rdar://problem/41852654
 

diff --git a/test/Sema/fixits-derived-conformances.swift b/test/Sema/fixits-derived-conformances.swift
@@ -0,0 +1,21 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift -emit-module -emit-library -module-name Types %S/Inputs/fixits-derived-conformances-multifile.swift -o %t/%target-library-name(Types)
+// RUN: %swift -typecheck -target %target-triple -I %t -diagnostics-editor-mode -verify %s
+
+import Types
+
+extension GenericEnum: Equatable { }
+// expected-error@-1 {{extension outside of file declaring generic enum 'GenericEnum' prevents automatic synthesis of '==' for protocol 'Equatable'}}
+// expected-note@-2 {{do you want to add protocol stubs?}}{{35-35=\n    public static func == (lhs: GenericEnum, rhs: GenericEnum) -> Bool {\n        <#code#>\n    \}\n}}
+
+extension Struct: Equatable { }
+// expected-error@-1 {{extension outside of file declaring struct 'Struct' prevents automatic synthesis of '==' for protocol 'Equatable'}}
+// expected-note@-2 {{do you want to add protocol stubs?}}{{30-30=\n    public static func == (lhs: Struct, rhs: Struct) -> Bool {\n        <#code#>\n    \}\n}}
+extension GenericStruct: Equatable { }
+// expected-error@-1 {{extension outside of file declaring generic struct 'GenericStruct' prevents automatic synthesis of '==' for protocol 'Equatable'}}
+// expected-note@-2 {{do you want to add protocol stubs?}}{{37-37=\n    public static func == (lhs: GenericStruct, rhs: GenericStruct) -> Bool {\n        <#code#>\n    \}\n}}
+
+extension Enum: CaseIterable { }
+// expected-error@-1 {{extension outside of file declaring enum 'Enum' prevents automatic synthesis of 'allCases' for protocol 'CaseIterable'}}
+// expected-note@-2 {{do you want to add protocol stubs?}}{{31-31=\n    public static var allCases: [Enum]\n}}
+
diff --git a/test/Sema/struct_equatable_hashable.swift b/test/Sema/struct_equatable_hashable.swift
@@ -196,7 +196,7 @@ extension OtherFileNonconforming: Hashable {
   func hash(into hasher: inout Hasher) {}
 }
 // ...but synthesis in a type defined in another file doesn't work yet.
-extension YetOtherFileNonconforming: Equatable {} // expected-error {{cannot be automatically synthesized in an extension in a different file to the type}}
+extension YetOtherFileNonconforming: Equatable {} // expected-error {{extension outside of file declaring struct 'YetOtherFileNonconforming' prevents automatic synthesis of '==' for protocol 'Equatable'}}
 
 // Verify that we can add Hashable conformance in an extension by only
 // implementing hash(into:)
@@ -253,7 +253,7 @@ extension UnusedGenericDeriveExtension: Hashable {}
 
 // Cross-file synthesis is still disallowed for conditional cases
 extension GenericOtherFileNonconforming: Equatable where T: Equatable {}
-// expected-error@-1{{implementation of 'Equatable' cannot be automatically synthesized in an extension in a different file to the type}}
+// expected-error@-1{{extension outside of file declaring generic struct 'GenericOtherFileNonconforming' prevents automatic synthesis of '==' for protocol 'Equatable'}}
 
 // rdar://problem/41852654