RequirementMachine: Record identity conformances in the property map

Author: slavapestov

lib/AST/RequirementMachine/PropertyMap.cpp

@@ -340,7 +340,11 @@ PropertyMap::buildPropertyMap(unsigned maxIterations,
     if (rule.isSimplified())
       continue;
 
-    if (rule.isPermanent())
+    // Identity conformances ([P].[P] => [P]) are permanent rules, but we
+    // keep them around to ensure that concrete conformance introduction
+    // works in the case where the protocol's Self type is itself subject
+    // to a superclass or concrete type requirement.
+    if (rule.isPermanent() && !rule.isIdentityConformanceRule())
       continue;
 
     // Collect all rules of the form T.[p] => T where T is canonical.

lib/AST/RequirementMachine/RequirementLowering.cpp

@@ -1003,6 +1003,7 @@ void RuleBuilder::collectRulesFromReferencedProtocols() {
       llvm::dbgs() << "protocol " << proto->getName() << " {\n";
     }
 
+    // Add the identity conformance rule [P].[P] => [P].
     MutableTerm lhs;
     lhs.add(Symbol::forProtocol(proto, Context));
     lhs.add(Symbol::forProtocol(proto, Context));

test/Generics/circular_protocol_superclass.swift

@@ -0,0 +1,11 @@
+// RUN: not %target-swift-frontend -typecheck %s -debug-generic-signatures -requirement-machine-protocol-signatures=on 2>&1 | %FileCheck %s
+
+// CHECK-LABEL: circular_protocol_superclass.(file).A@
+// CHECK-NEXT: Requirement signature: <Self where Self : a>
+protocol A : a {
+  associatedtype e : a
+}
+
+class a : A {
+  typealias e = a
+}

test/Generics/rdar79564324.swift

@@ -38,6 +38,7 @@ public func test<T : P>(_ t: T) where T == T.A {
 // CHECK-NEXT: Rewrite loops: {
 // CHECK:      }
 // CHECK-NEXT: Property map: {
+// CHECK-NEXT:   [P] => { conforms_to: [P] }
 // CHECK-NEXT:   [P:A] => { conforms_to: [P] }
 // CHECK-NEXT:   τ_0_1 => { conforms_to: [P] }
 // CHECK-NEXT:   τ_0_0 => { conforms_to: [P] }

test/Generics/unify_superclass_types_1.swift

@@ -26,6 +26,6 @@ extension P where Self : Derived {
 // CHECK-NEXT: Rewrite loops: {
 // CHECK:      }
 // CHECK-NEXT: Property map: {
-// CHECK-NEXT:   [P] => { layout: _NativeClass superclass: [superclass: Base] }
+// CHECK-NEXT:   [P] => { conforms_to: [P] layout: _NativeClass superclass: [superclass: Base] }
 // CHECK-NEXT:   τ_0_0 => { conforms_to: [P] layout: _NativeClass superclass: [superclass: Derived] }
 // CHECK-NEXT: }

test/Generics/unify_superclass_types_2.swift

@@ -44,6 +44,8 @@ func unifySuperclassTest<T : P1 & P2>(_: T) {
 // CHECK-NEXT: Rewrite loops: {
 // CHECK:      }
 // CHECK-NEXT: Property map: {
+// CHECK-NEXT:   [P1] => { conforms_to: [P1] }
+// CHECK-NEXT:   [P2] => { conforms_to: [P2] }
 // CHECK-NEXT:   [P1:X] => { layout: _NativeClass superclass: [superclass: Generic<Int, τ_0_0, τ_0_1> with <[P1:A1], [P1:B1]>] }
 // CHECK-NEXT:   [P2:X] => { layout: _NativeClass superclass: [superclass: Generic<τ_0_0, String, τ_0_1> with <[P2:A2], [P2:B2]>] }
 // CHECK-NEXT:   τ_0_0 => { conforms_to: [P1 P2] }

test/Generics/unify_superclass_types_3.swift

@@ -48,6 +48,8 @@ func unifySuperclassTest<T : P1 & P2>(_: T) {
 // CHECK-NEXT: Rewrite loops: {
 // CHECK:      }
 // CHECK-NEXT: Property map: {
+// CHECK-NEXT:   [P1] => { conforms_to: [P1] }
+// CHECK-NEXT:   [P2] => { conforms_to: [P2] }
 // CHECK-NEXT:   [P1:X] => { layout: _NativeClass superclass: [superclass: Derived<τ_0_0, τ_0_1> with <[P1:A1], [P1:B1]>] }
 // CHECK-NEXT:   [P2:X] => { layout: _NativeClass superclass: [superclass: Generic<τ_0_0, String, τ_0_1> with <[P2:A2], [P2:B2]>] }
 // CHECK-NEXT:   τ_0_0 => { conforms_to: [P1 P2] }

test/Generics/unify_superclass_types_4.swift

@@ -47,6 +47,9 @@ func unifySuperclassTest<T : P1 & P2>(_: T) {
 // CHECK-NEXT: Rewrite loops: {
 // CHECK:      }
 // CHECK-NEXT: Property map: {
+// CHECK-NEXT:   [P1] => { conforms_to: [P1] }
+// CHECK-NEXT:   [P2] => { conforms_to: [P2] }
+// CHECK-NEXT:   [Q] => { conforms_to: [Q] }
 // CHECK-NEXT:   [P1:X] => { layout: _NativeClass superclass: [superclass: Base<τ_0_0> with <[P1:A1]>] }
 // CHECK-NEXT:   [P2:A2] => { conforms_to: [Q] }
 // CHECK-NEXT:   [P2:X] => { layout: _NativeClass superclass: [superclass: Derived<τ_0_0> with <[P2:A2]>] }