Sema: Reject 'any P' in inheritance clauses

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -2784,9 +2784,11 @@ WARNING(anyobject_class_inheritance_deprecated,Deprecation,
 ERROR(multiple_inheritance,none,
   "multiple inheritance from classes %0 and %1", (Type, Type))
 ERROR(inheritance_from_non_protocol_or_class,none,
-  "inheritance from non-protocol, non-class type %0", (Type))
+  "inheritance from non-protocol, non-class type '%0'", (StringRef))
 ERROR(inheritance_from_non_protocol,none,
-  "inheritance from non-protocol type %0", (Type))
+  "inheritance from non-protocol type '%0'", (StringRef))
+ERROR(inheritance_from_anyobject,none,
+  "only protocols can inherit from 'AnyObject'", ())
 ERROR(inheritance_from_parameterized_protocol,none,
   "cannot inherit from protocol type with generic argument %0", (Type))
 ERROR(superclass_not_first,none,

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -212,7 +212,15 @@ static void checkInheritanceClause(
       inheritedAnyObject = { i, inherited.getSourceRange() };
     }
 
-    if (inheritedTy->isExistentialType()) {
+    if (inheritedTy->is<ParameterizedProtocolType>()) {
+      if (!isa<ProtocolDecl>(decl)) {
+        decl->diagnose(diag::inheritance_from_parameterized_protocol,
+                       inheritedTy);
+      }
+      continue;
+    }
+
+    if (inheritedTy->isConstraintType()) {
       auto layout = inheritedTy->getExistentialLayout();
 
       // Subclass existentials are not allowed except on classes and
@@ -227,10 +235,7 @@ static void checkInheritanceClause(
       // AnyObject is not allowed except on protocols.
       if (layout.hasExplicitAnyObject &&
           !isa<ProtocolDecl>(decl)) {
-        decl->diagnose(canHaveSuperclass
-                       ? diag::inheritance_from_non_protocol_or_class
-                       : diag::inheritance_from_non_protocol,
-                       inheritedTy);
+        decl->diagnose(diag::inheritance_from_anyobject);
         continue;
       }
 
@@ -249,14 +254,6 @@ static void checkInheritanceClause(
       inheritedTy = layout.explicitSuperclass;
     }
 
-    if (inheritedTy->is<ParameterizedProtocolType>()) {
-      if (!isa<ProtocolDecl>(decl)) {
-        decl->diagnose(diag::inheritance_from_parameterized_protocol,
-                       inheritedTy);
-      }
-      continue;
-    }
-
     // If this is an enum inheritance clause, check for a raw type.
     if (isa<EnumDecl>(decl)) {
       // Check if we already had a raw type.
@@ -338,11 +335,19 @@ static void checkInheritanceClause(
       }
     }
 
+    // FIXME: The inherited type is printed directly here because
+    // the current default is to not print `any` for existential
+    // types, but this error message is super confusing without `any`
+    // if the user wrote it explicitly.
+    PrintOptions options;
+    options.PrintExplicitAny = true;
+    auto inheritedTyString = inheritedTy.getString(options);
+
     // We can't inherit from a non-class, non-protocol type.
     decl->diagnose(canHaveSuperclass
                    ? diag::inheritance_from_non_protocol_or_class
                    : diag::inheritance_from_non_protocol,
-                   inheritedTy);
+                   inheritedTyString);
     // FIXME: Note pointing to the declaration 'inheritedTy' references?
   }
 }

lib/Sema/TypeCheckRequestFunctions.cpp

@@ -142,8 +142,8 @@ Type EnumRawTypeRequest::evaluate(Evaluator &evaluator,
     auto &inheritedType = *inheritedTypeResult;
     if (!inheritedType) continue;
 
-    // Skip existential types.
-    if (inheritedType->isExistentialType()) continue;
+    // Skip protocol conformances.
+    if (inheritedType->isConstraintType()) continue;
 
     // We found a raw type; return it.
     return inheritedType;

test/decl/protocol/conforms/placement.swift

@@ -105,20 +105,20 @@ extension ExplicitSub1 : P1 { } // expected-error{{redundant conformance of 'Exp
 // ---------------------------------------------------------------------------
 // Suppression of synthesized conformances
 // ---------------------------------------------------------------------------
-class SynthesizedClass1 : AnyObject { } // expected-error{{inheritance from non-protocol, non-class type 'AnyObject'}}
+class SynthesizedClass1 : AnyObject { } // expected-error{{only protocols can inherit from 'AnyObject'}}
 
 class SynthesizedClass2 { }
-extension SynthesizedClass2 : AnyObject { } // expected-error{{inheritance from non-protocol type 'AnyObject'}}
+extension SynthesizedClass2 : AnyObject { } // expected-error{{only protocols can inherit from 'AnyObject'}}
 
 class SynthesizedClass3 : AnyObjectRefinement { }
 
 class SynthesizedClass4 { }
 extension SynthesizedClass4 : AnyObjectRefinement { }
 
-class SynthesizedSubClass1 : SynthesizedClass1, AnyObject { } // expected-error{{inheritance from non-protocol, non-class type 'AnyObject'}}
+class SynthesizedSubClass1 : SynthesizedClass1, AnyObject { } // expected-error{{only protocols can inherit from 'AnyObject'}}
 
 class SynthesizedSubClass2 : SynthesizedClass2 { }
-extension SynthesizedSubClass2 : AnyObject { } // expected-error{{inheritance from non-protocol type 'AnyObject'}}
+extension SynthesizedSubClass2 : AnyObject { } // expected-error{{only protocols can inherit from 'AnyObject'}}
 
 class SynthesizedSubClass3 : SynthesizedClass1, AnyObjectRefinement { }
 
@@ -169,12 +169,12 @@ extension MFExplicitSub1 : P1 { } // expected-error{{redundant conformance of 'M
 // ---------------------------------------------------------------------------
 class MFSynthesizedClass1 { }
 
-extension MFSynthesizedClass2 : AnyObject { } // expected-error{{inheritance from non-protocol type 'AnyObject'}}
+extension MFSynthesizedClass2 : AnyObject { } // expected-error{{only protocols can inherit from 'AnyObject'}}
 
 class MFSynthesizedClass4 { }
 extension MFSynthesizedClass4 : AnyObjectRefinement { }
 
-extension MFSynthesizedSubClass2 : AnyObject { } // expected-error{{inheritance from non-protocol type 'AnyObject'}}
+extension MFSynthesizedSubClass2 : AnyObject { } // expected-error{{only protocols can inherit from 'AnyObject'}}
 
 extension MFSynthesizedSubClass3 : AnyObjectRefinement { }
 
@@ -198,7 +198,7 @@ extension MMSuper1 : MMP1 { } // expected-warning{{conformance of 'MMSuper1' to
 extension MMSuper1 : MMP2a { } // expected-warning{{conformance of 'MMSuper1' to protocol 'MMP2a' was already stated in the type's module 'placement_module_A'}}
 extension MMSuper1 : MMP3b { } // okay
 
-extension MMSub1 : AnyObject { } // expected-error{{inheritance from non-protocol type 'AnyObject'}}
+extension MMSub1 : AnyObject { } // expected-error{{only protocols can inherit from 'AnyObject'}}
 
 extension MMSub2 : MMP1 { } // expected-warning{{conformance of 'MMSub2' to protocol 'MMP1' was already stated in the type's module 'placement_module_A'}}
 extension MMSub2 : MMP2a { } // expected-warning{{conformance of 'MMSub2' to protocol 'MMP2a' was already stated in the type's module 'placement_module_A'}}
@@ -209,7 +209,7 @@ extension MMSub2 : MMAnyObjectRefinement { } // okay
 extension MMSub3 : MMP1 { } // expected-warning{{conformance of 'MMSub3' to protocol 'MMP1' was already stated in the type's module 'placement_module_A'}}
 extension MMSub3 : MMP2a { } // expected-warning{{conformance of 'MMSub3' to protocol 'MMP2a' was already stated in the type's module 'placement_module_A'}}
 extension MMSub3 : MMP3b { } // okay
-extension MMSub3 : AnyObject { } // expected-error{{inheritance from non-protocol type 'AnyObject'}}
+extension MMSub3 : AnyObject { } // expected-error{{only protocols can inherit from 'AnyObject'}}
 
 extension MMSub4 : MMP1 { } // expected-warning{{conformance of 'MMSub4' to protocol 'MMP1' was already stated in the type's module 'placement_module_B'}}
 extension MMSub4 : MMP2a { } // expected-warning{{conformance of 'MMSub4' to protocol 'MMP2a' was already stated in the type's module 'placement_module_B'}}

test/type/explicit_existential.swift

@@ -257,3 +257,24 @@ func testConstraintAlias(x: Constraint) {} // expected-warning{{'Constraint' (ak
 
 typealias Existential = any Input
 func testExistentialAlias(x: Existential, y: any Constraint) {}
+
+// Reject explicit existential types in inheritance clauses
+protocol Empty {}
+
+struct S : any Empty {} // expected-error {{inheritance from non-protocol type 'any Empty'}}
+class C : any Empty {} // expected-error {{inheritance from non-protocol, non-class type 'any Empty'}}
+
+// FIXME: Diagnostics are not great in the enum case because we confuse this with a raw type
+
+enum E : any Empty { // expected-error {{raw type 'Empty' is not expressible by a string, integer, or floating-point literal}}
+// expected-error@-1 {{'E' declares raw type 'Empty', but does not conform to RawRepresentable and conformance could not be synthesized}}
+// expected-error@-2 {{RawRepresentable conformance cannot be synthesized because raw type 'Empty' is not Equatable}}
+  case hack
+}
+
+enum EE : Equatable, any Empty { // expected-error {{raw type 'Empty' is not expressible by a string, integer, or floating-point literal}}
+// expected-error@-1 {{'EE' declares raw type 'Empty', but does not conform to RawRepresentable and conformance could not be synthesized}}
+// expected-error@-2 {{RawRepresentable conformance cannot be synthesized because raw type 'Empty' is not Equatable}}
+// expected-error@-3 {{raw type 'Empty' must appear first in the enum inheritance clause}}
+  case hack
+}