GSB: Don't infer requirements from type constructors in a protocol inheritance clause

This enabled a gross idiom that should not have been allowed in the first place:

    typealias G<T> = Any where T : P

    protocol P {}
    protocol Q : G<Self> {} // Q inherits from P now!

I'd like to ban this, assuming nothing is actually relying on this behavior.

Author: slavapestov

lib/AST/GenericSignatureBuilder.cpp

@@ -4012,7 +4012,7 @@ ConstraintResult GenericSignatureBuilder::expandConformanceRequirement(
     // Add all of the inherited protocol requirements, recursively.
     auto inheritedReqResult =
       addInheritedRequirements(proto, selfType.getUnresolvedType(), source,
-                               proto->getModuleContext());
+                               nullptr);
     if (isErrorResult(inheritedReqResult))
       return inheritedReqResult;
   }

test/Generics/requirement_inference.swift

@@ -508,13 +508,15 @@ extension X1WithP2MoreArgs {
   }
 }
 
-// Inference from protocol inheritance clauses.
+// Inference from protocol inheritance clauses is not allowed.
 typealias ExistentialP4WithP2Assoc<T: P4> = P4 where T.P4Assoc : P2
 
 protocol P37 : ExistentialP4WithP2Assoc<Self> { }
+// expected-error@-1 {{type 'Self.P4Assoc' does not conform to protocol 'P2'}}
 
 extension P37 {
   func f() {
-    _ = X5<P4Assoc>() // requires P2
+    _ = X5<P4Assoc>()
+    // expected-error@-1 {{type 'Self.P4Assoc' does not conform to protocol 'P2'}}
   }
 }

validation-test/compiler_crashers_2_fixed/0122-rdar30965000.swift

@@ -1,9 +1,9 @@
-// RUN: %target-swift-frontend %s -emit-ir -o /dev/null
+// RUN: %target-typecheck-verify-swift
 
 protocol P {
   associatedtype A
 }
 struct Straint<C: P> where C.A : P {
  typealias X = Any 
 }
-protocol Q : Straint<Self>.X {}
+protocol Q : Straint<Self>.X {} // expected-error {{type 'Self' does not conform to protocol 'P'}}