RequirementMachine: Skip 'verify' check if completion failed

We obviously don't have a valid generic signature in this case.

Author: slavapestov

lib/AST/GenericSignatureBuilder.cpp

@@ -8276,6 +8276,7 @@ AbstractGenericSignatureRequest::evaluate(
       return rqmResult;
 
     if (!rqmResult.getInt().contains(GenericSignatureErrorFlags::HasConflict) &&
+        !rqmResult.getInt().contains(GenericSignatureErrorFlags::CompletionFailed) &&
         !rqmResult.getPointer()->isEqual(gsbResult.getPointer())) {
       PrintOptions opts;
       opts.ProtocolQualifiedDependentMemberTypes = true;
@@ -8489,6 +8490,7 @@ InferredGenericSignatureRequest::evaluate(
       return rqmResult;
 
     if (!rqmResult.getInt().contains(GenericSignatureErrorFlags::HasConflict) &&
+        !rqmResult.getInt().contains(GenericSignatureErrorFlags::CompletionFailed) &&
         !rqmResult.getPointer()->isEqual(gsbResult.getPointer())) {
       PrintOptions opts;
       opts.ProtocolQualifiedDependentMemberTypes = true;
@@ -8692,6 +8694,7 @@ RequirementSignatureRequest::evaluate(Evaluator &evaluator,
     auto gsbResult = buildViaGSB();
 
     if (!rqmResult.getErrors().contains(GenericSignatureErrorFlags::HasConflict) &&
+        !rqmResult.getErrors().contains(GenericSignatureErrorFlags::CompletionFailed) &&
         !compare(rqmResult.getRequirements(),
                  gsbResult.getRequirements())) {
       PrintOptions opts;

test/decl/protocol/req/recursion.swift

@@ -1,16 +1,20 @@
-// RUN: %target-typecheck-verify-swift
+// RUN: %target-typecheck-verify-swift -requirement-machine-inferred-signatures=verify
 
 protocol SomeProtocol {
 	associatedtype T
 }
 
 extension SomeProtocol where T == Optional<T> { } // expected-error{{same-type constraint 'Self.T' == 'Optional<Self.T>' is recursive}}
+// expected-error@-1 {{cannot build rewrite system for generic signature; concrete nesting limit exceeded}}
+// expected-note@-2 {{failed rewrite rule is τ_0_0.[SomeProtocol:T].[concrete: Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<τ_0_0.[SomeProtocol:T]>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>] => τ_0_0.[SomeProtocol:T]}}
 
 // rdar://problem/19840527
 
 class X<T> where T == X { // expected-error{{same-type constraint 'T' == 'X<T>' is recursive}}
-// expected-error@-1{{same-type requirement makes generic parameter 'T' non-generic}}
-// expected-error@-2 3{{generic class 'X' has self-referential generic requirements}}
+// expected-error@-1 {{cannot build rewrite system for generic signature; concrete nesting limit exceeded}}
+// expected-note@-2 {{failed rewrite rule is τ_0_0.[concrete: X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<X<τ_0_0>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>] => τ_0_0}}
+// expected-error@-3{{same-type requirement makes generic parameter 'T' non-generic}}
+// expected-error@-4 6{{generic class 'X' has self-referential generic requirements}}
     var type: T { return Swift.type(of: self) } // expected-error{{cannot convert return expression of type 'X<T>.Type' to return type 'T'}}
 }
 
@@ -45,7 +49,7 @@ public protocol P {
 }
 
 public struct S<A: P> where A.T == S<A> {
-// expected-error@-1 3{{generic struct 'S' has self-referential generic requirements}}
+// expected-error@-1 6{{generic struct 'S' has self-referential generic requirements}}
   func f(a: A.T) {
     g(a: id(t: a)) // `a` has error type which is diagnosed as circular reference
     _ = A.T.self
@@ -70,7 +74,7 @@ protocol PI {
 }
 
 struct SI<A: PI> : I where A : I, A.T == SI<A> {
-// expected-error@-1 3{{generic struct 'SI' has self-referential generic requirements}}
+// expected-error@-1 6{{generic struct 'SI' has self-referential generic requirements}}
   func ggg<T : I>(t: T.Type) -> T {
     return T()
   }
@@ -97,9 +101,9 @@ struct S5<A: PI> : I where A : I, A.T == S4<A> { }
 
 // Used to hit ArchetypeBuilder assertions
 struct SU<A: P> where A.T == SU {
-// expected-error@-1 3{{generic struct 'SU' has self-referential generic requirements}}
+// expected-error@-1 6{{generic struct 'SU' has self-referential generic requirements}}
 }
 
 struct SIU<A: PI> : I where A : I, A.T == SIU {
-// expected-error@-1 3{{generic struct 'SIU' has self-referential generic requirements}}
+// expected-error@-1 6{{generic struct 'SIU' has self-referential generic requirements}}
 }