[Diagnostics] For now, don't diagnose layout requirement failures

in MissingConformanceFailure::diagnoseTypeCannotConform.

Author: hborla

lib/Sema/CSDiagnostics.cpp

@@ -603,7 +603,8 @@ bool MissingConformanceFailure::diagnoseAsError() {
 
 bool MissingConformanceFailure::diagnoseTypeCannotConform(Expr *anchor,
     Type nonConformingType, Type protocolType) const {
-  if (!(nonConformingType->is<AnyFunctionType>() ||
+  if (getRequirement().getKind() == RequirementKind::Layout ||
+      !(nonConformingType->is<AnyFunctionType>() ||
       nonConformingType->is<TupleType>() ||
       nonConformingType->isExistentialType() ||
       nonConformingType->is<AnyMetatypeType>())) {

test/Generics/existential_restrictions.swift

@@ -16,15 +16,15 @@ func fOP<T : OP>(_ t: T) { }
 func fOPE(_ t: OP) { }
 func fSP<T : SP>(_ t: T) { }
 func fAO<T : AnyObject>(_ t: T) { }
-// expected-note@-1 {{required by global function 'fAO' where 'T' = 'P'}}
-// expected-note@-2 {{required by global function 'fAO' where 'T' = 'CP'}}
-// expected-note@-3 {{required by global function 'fAO' where 'T' = 'OP & P'}}
+// expected-note@-1 {{where 'T' = 'P'}}
+// expected-note@-2 {{where 'T' = 'CP'}}
+// expected-note@-3 {{where 'T' = 'OP & P'}}
 func fAOE(_ t: AnyObject) { }
 func fT<T>(_ t: T) { }
 
 func testPassExistential(_ p: P, op: OP, opp: OP & P, cp: CP, sp: SP, any: Any, ao: AnyObject) {
   fP(p) // expected-error{{value of protocol type 'P' cannot conform to 'P'; only struct/enum/class types can conform to protocols}}
-  fAO(p) // expected-error{{value of protocol type 'P' cannot conform to 'AnyObject'; only struct/enum/class types can conform to protocols}}
+  fAO(p) // expected-error{{global function 'fAO' requires that 'P' be a class type}}
   fAOE(p) // expected-error{{argument type 'P' does not conform to expected type 'AnyObject'}}
   fT(p)
 
@@ -33,13 +33,13 @@ func testPassExistential(_ p: P, op: OP, opp: OP & P, cp: CP, sp: SP, any: Any,
   fAOE(op)
   fT(op)
 
-  fAO(cp) // expected-error{{value of protocol type 'CP' cannot conform to 'AnyObject'; only struct/enum/class types can conform to protocols}}
+  fAO(cp) // expected-error{{global function 'fAO' requires that 'CP' be a class type}}
   fAOE(cp)
   fT(cp)
 
   fP(opp) // expected-error{{value of protocol type 'OP & P' cannot conform to 'P'; only struct/enum/class types can conform to protocols}}
   fOP(opp) // expected-error{{value of protocol type 'OP & P' cannot conform to 'OP'; only struct/enum/class types can conform to protocols}}
-  fAO(opp) // expected-error{{value of protocol type 'OP & P' cannot conform to 'AnyObject'; only struct/enum/class types can conform to protocols}}
+  fAO(opp) // expected-error{{global function 'fAO' requires that 'OP & P' be a class type}}
   fAOE(opp)
   fT(opp)
 

test/type/subclass_composition.swift

@@ -299,7 +299,7 @@ func dependentMemberTypes<T : BaseIntAndP2>(
   _: BaseIntAndP2.FullyConcrete) {}
 
 func conformsToAnyObject<T : AnyObject>(_: T) {}
-// expected-note@-1 {{required by global function 'conformsToAnyObject' where 'T' = 'P1'}}
+// expected-note@-1 {{where 'T' = 'P1'}}
 func conformsToP1<T : P1>(_: T) {}
 // expected-note@-1 {{required by global function 'conformsToP1' where 'T' = 'P1'}}
 func conformsToP2<T : P2>(_: T) {}
@@ -411,7 +411,7 @@ func conformsTo<T1 : P2, T2 : Base<Int> & P2>(
 
   // Errors
   conformsToAnyObject(p1)
-  // expected-error@-1 {{value of protocol type 'P1' cannot conform to 'AnyObject'; only struct/enum/class types can conform to protocols}}
+  // expected-error@-1 {{global function 'conformsToAnyObject' requires that 'P1' be a class type}}
 
   conformsToP1(p1)
   // expected-error@-1 {{value of protocol type 'P1' cannot conform to 'P1'; only struct/enum/class types can conform to protocols}}