RequirementMachine: Perform concrete contraction on protocol requirement signatures

lib/AST/RequirementMachine/RequirementMachineRequests.cpp

@@ -287,6 +287,8 @@ RequirementSignatureRequestRQM::evaluate(Evaluator &evaluator,
     rewriteCtx.finishComputingRequirementSignatures(proto);
   };
 
+  SmallVector<RequirementError, 4> errors;
+
   // Collect user-written requirements from the protocols in this connected
   // component.
   llvm::DenseMap<const ProtocolDecl *,
@@ -297,6 +299,20 @@ RequirementSignatureRequestRQM::evaluate(Evaluator &evaluator,
       requirements.push_back(req);
     for (auto req : proto->getTypeAliasRequirements())
       requirements.push_back({req, SourceLoc(), /*inferred=*/false});
+
+    // Preprocess requirements to eliminate conformances on type parameters
+    // which are made concrete.
+    if (ctx.LangOpts.EnableRequirementMachineConcreteContraction) {
+      SmallVector<StructuralRequirement, 4> contractedRequirements;
+
+      bool debug = rewriteCtx.getDebugOptions()
+                             .contains(DebugFlags::ConcreteContraction);
+
+      if (performConcreteContraction(requirements, contractedRequirements,
+                                     errors, debug)) {
+        std::swap(contractedRequirements, requirements);
+      }
+    }
   }
 
   if (rewriteCtx.getDebugOptions().contains(DebugFlags::Timers)) {
@@ -409,7 +425,6 @@ RequirementSignatureRequestRQM::evaluate(Evaluator &evaluator,
     // Diagnose redundant requirements and conflicting requirements.
     if (ctx.LangOpts.RequirementMachineProtocolSignatures ==
         RequirementMachineMode::Enabled) {
-      SmallVector<RequirementError, 4> errors;
       machine->computeRequirementDiagnostics(errors, proto->getLoc());
       diagnoseRequirementErrors(ctx, errors,
                                 AllowConcreteTypePolicy::NestedAssocTypes);

test/Generics/concrete_conformances_in_protocol.swift

@@ -1,8 +1,6 @@
+// RUN: %target-typecheck-verify-swift
 // RUN: %target-swift-frontend -typecheck %s -debug-generic-signatures 2>&1 | %FileCheck %s
 
-// rdar://problem/88135912
-// XFAIL: *
-
 protocol P {
   associatedtype T
 }
@@ -15,6 +13,7 @@ struct S : P {
 
 protocol R0 {
   associatedtype A where A : P, A == S
+  // expected-warning@-1 {{redundant conformance constraint 'S' : 'P'}}
 }
 
 ////
@@ -27,6 +26,7 @@ struct G<T> : P {}
 protocol R1 {
   associatedtype A
   associatedtype B where B : P, B == G<A>
+  // expected-warning@-1 {{redundant conformance constraint 'G<Self.A>' : 'P'}}
 }
 
 // CHECK-LABEL: concrete_conformances_in_protocol.(file).R2@
@@ -34,6 +34,7 @@ protocol R1 {
 
 protocol R2 {
   associatedtype A where A : P, A == G<B>
+  // expected-warning@-1 {{redundant conformance constraint 'G<Self.B>' : 'P'}}
   associatedtype B
 }
 
@@ -51,6 +52,7 @@ struct GG<T : P> : PP {}
 protocol RR3 {
   associatedtype A : P
   associatedtype B where B : PP, B == GG<A>
+  // expected-warning@-1 {{redundant conformance constraint 'GG<Self.A>' : 'PP'}}
 }
 
 // CHECK-LABEL: concrete_conformances_in_protocol.(file).RR4@
@@ -58,6 +60,7 @@ protocol RR3 {
 
 protocol RR4 {
   associatedtype A where A : PP, A == GG<B>
+  // expected-warning@-1 {{redundant conformance constraint 'GG<Self.B>' : 'PP'}}
   associatedtype B : P
 }
 
@@ -67,6 +70,7 @@ protocol RR4 {
 protocol RR5 {
   associatedtype A : PP
   associatedtype B where B : PP, B == GG<A.T>
+  // expected-warning@-1 {{redundant conformance constraint 'GG<Self.A.T>' : 'PP'}}
 }
 
 // CHECK-LABEL: concrete_conformances_in_protocol.(file).RR6@
@@ -74,5 +78,24 @@ protocol RR5 {
 
 protocol RR6 {
   associatedtype A where A : PP, A == GG<B.T>
+  // expected-warning@-1 {{redundant conformance constraint 'GG<Self.B.T>' : 'PP'}}
   associatedtype B : PP
 }
+
+protocol P1 {
+  associatedtype T : P1
+}
+
+struct GGG<U : P1> : P1 {
+  typealias T = GGG<GGG<U>>
+}
+
+// CHECK-LABEL: concrete_conformances_in_protocol.(file).P2@
+// CHECK-LABEL: Requirement signature: <Self where Self.[P2]T == GGG<Self.[P2]U>, Self.[P2]U : P1>
+
+protocol P2 {
+  associatedtype T : P1 where T == GGG<U>
+  // expected-warning@-1 {{redundant conformance constraint 'GGG<Self.U>' : 'P1'}}
+  associatedtype U : P1
+}
+

test/Generics/conditional_requirement_inference_in_protocol.swift

@@ -1,18 +1,22 @@
-// RUN: %target-typecheck-verify-swift -requirement-machine-protocol-signatures=verify -requirement-machine-inferred-signatures=verify
-// RUN: %target-swift-frontend -typecheck %s -debug-generic-signatures -requirement-machine-protocol-signatures=verify -requirement-machine-inferred-signatures=verify 2>&1 | %FileCheck %s
+// RUN: %target-typecheck-verify-swift -requirement-machine-protocol-signatures=on -requirement-machine-inferred-signatures=on
+// RUN: %target-swift-frontend -typecheck %s -debug-generic-signatures -requirement-machine-protocol-signatures=on -requirement-machine-inferred-signatures=on 2>&1 | %FileCheck %s
+
+// FIXME: The redundant conformance warnings here should not be emitted, since
+// these requirements participate in conditional requirement inference.
 
 // CHECK-LABEL: conditional_requirement_inference_in_protocol.(file).Good@
 // CHECK-LABEL: Requirement signature: <Self where Self.[Good]T == [Self.[Good]U], Self.[Good]U : Equatable>
 
 protocol Good {
-  associatedtype T : Equatable // expected-warning {{redundant conformance constraint 'Self.T' : 'Equatable'}}
-  associatedtype U : Equatable where T == Array<U> // expected-note {{conformance constraint 'Self.T' : 'Equatable' implied here}}
+  associatedtype T : Equatable // expected-warning {{redundant conformance constraint 'Array<Self.U>' : 'Equatable'}}
+  associatedtype U : Equatable where T == Array<U>
+  // expected-warning@-1 {{redundant conformance constraint 'Self.U' : 'Equatable'}}
 }
 
 // CHECK-LABEL: conditional_requirement_inference_in_protocol.(file).Bad@
-// CHECK-LABEL: Requirement signature: <Self where Self.[Bad]T == [Self.[Bad]U]>
+// CHECK-LABEL: Requirement signature: <Self where Self.[Bad]T == [Self.[Bad]U], Self.[Bad]U : Equatable>
 
 protocol Bad {
-  associatedtype T : Equatable // expected-warning {{redundant conformance constraint 'Self.T' : 'Equatable'}}
-  associatedtype U where T == Array<U> // expected-note {{conformance constraint 'Self.T' : 'Equatable' implied here}}
+  associatedtype T : Equatable // expected-warning {{redundant conformance constraint 'Array<Self.U>' : 'Equatable'}}
+  associatedtype U where T == Array<U>
 }

test/Generics/derived_via_concrete_in_protocol.swift

@@ -1,9 +1,5 @@
-// RUN: %target-typecheck-verify-swift -requirement-machine-protocol-signatures=off
-// RUN: %target-swift-frontend -debug-generic-signatures -typecheck %s -requirement-machine-protocol-signatures=off 2>&1 | %FileCheck %s
-
-// FIXME: Implement concrete contraction for the Requirement Machine's
-// RequirementSignatureRequest to get this to pass without turning off
-// -requirement-machine-protocol-signatures.
+// RUN: %target-typecheck-verify-swift -requirement-machine-protocol-signatures=on
+// RUN: %target-swift-frontend -debug-generic-signatures -typecheck %s -requirement-machine-protocol-signatures=on 2>&1 | %FileCheck %s
 
 protocol P24 {
   associatedtype C: P20
@@ -29,8 +25,8 @@ class X3 { }
 // CHECK-NEXT: Requirement signature: <Self where Self.[P25a]A == X24<Self.[P25a]B>, Self.[P25a]B : P20>
 // CHECK-NEXT: Canonical requirement signature: <τ_0_0 where τ_0_0.[P25a]A == X24<τ_0_0.[P25a]B>, τ_0_0.[P25a]B : P20>
 protocol P25a {
-  associatedtype A: P24 // expected-warning{{redundant conformance constraint 'Self.A' : 'P24'}}
-  associatedtype B: P20 where A == X24<B> // expected-note{{conformance constraint 'Self.A' : 'P24' implied here}}
+  associatedtype A: P24 // expected-warning{{redundant conformance constraint 'X24<Self.B>' : 'P24'}}
+  associatedtype B: P20 where A == X24<B>
 }
 
 // CHECK-LABEL: .P25b@
@@ -45,9 +41,9 @@ protocol P25b {
 // CHECK-NEXT: Requirement signature: <Self where Self.[P27a]A == X26<Self.[P27a]B>, Self.[P27a]B : X3>
 // CHECK-NEXT: Canonical requirement signature: <τ_0_0 where τ_0_0.[P27a]A == X26<τ_0_0.[P27a]B>, τ_0_0.[P27a]B : X3>
 protocol P27a {
-  associatedtype A: P26 // expected-warning{{redundant conformance constraint 'Self.A' : 'P26'}}
+  associatedtype A: P26 // expected-warning{{redundant conformance constraint 'X26<Self.B>' : 'P26'}}
 
-  associatedtype B: X3 where A == X26<B> // expected-note{{conformance constraint 'Self.A' : 'P26' implied here}}
+  associatedtype B: X3 where A == X26<B>
 }
 
 // CHECK-LABEL: .P27b@

test/Generics/non_confluent.swift

@@ -43,11 +43,12 @@ struct S<U : P1> : P1 {
   typealias T = S<S<U>>
 }
 
-protocol P3 {
-// expected-error@-1 {{cannot build rewrite system for protocol; rule length limit exceeded}}
-// expected-note@-2 {{failed rewrite rule is [P3:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[concrete: S<S<S<S<S<S<S<S<S<S<S<S<S<S<[P3:U]>>>>>>>>>>>>>>] => [P3:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T]}}
-
-  associatedtype T : P1 where T == S<U>
-// expected-error@-1 {{type 'Self.U' does not conform to protocol 'P1'}}
+protocol P3Base {
+  associatedtype T : P1
   associatedtype U : P1
 }
+
+protocol P3 : P3Base where T == S<U> {
+// expected-error@-1 {{cannot build rewrite system for protocol; rule length limit exceeded}}
+// expected-note@-2 {{failed rewrite rule is [P3:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[concrete: S<S<S<S<S<S<S<S<S<S<S<S<S<S<[P3:U]>>>>>>>>>>>>>>] => [P3:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T].[P1:T]}}
+}

validation-test/compiler_crashers_2_fixed/rdar56398071.swift

@@ -1,6 +1,4 @@
-// RUN: %target-swift-frontend -primary-file %s -emit-ir -requirement-machine-protocol-signatures=off
-
-// TODO: Get this to pass with  -requirement-machine-protocol-signatures=on.
+// RUN: %target-swift-frontend -primary-file %s -emit-ir -requirement-machine-protocol-signatures=on
 
 public protocol WrappedSignedInteger: SignedInteger where Stride == Int {
     typealias WrappedInteger = Int

validation-test/compiler_crashers_2_fixed/sr11639.swift

@@ -1,6 +1,4 @@
-// RUN: %target-swift-frontend -emit-ir -primary-file %s -debug-generic-signatures -requirement-machine-protocol-signatures=off 2>&1 | %FileCheck %s
-
-// FIXME: Get this working with -requirement-machine-protocol-signatures=on again
+// RUN: %target-swift-frontend -emit-ir -primary-file %s -debug-generic-signatures -requirement-machine-protocol-signatures=on 2>&1 | %FileCheck %s
 
 public protocol FooProtocol {
   associatedtype Bar