[CSBindings] Record all of the protocol requirements (not just literal)

Author: xedin

include/swift/Sema/ConstraintSystem.h

@@ -4706,7 +4706,7 @@ class ConstraintSystem {
     SmallVector<PotentialBinding, 4> Bindings;
 
     /// The set of protocol requirements placed on this type variable.
-    llvm::TinyPtrVector<Constraint *> Protocols;
+    llvm::SmallVector<Constraint *, 4> Protocols;
 
     /// The set of constraints which would be used to infer default types.
     llvm::TinyPtrVector<Constraint *> Defaults;

lib/Sema/CSBindings.cpp

@@ -986,8 +986,13 @@ bool ConstraintSystem::PotentialBindings::infer(
     break;
 
   case ConstraintKind::ConformsTo:
-  case ConstraintKind::SelfObjectOfProtocol:
-    return false;
+  case ConstraintKind::SelfObjectOfProtocol: {
+    auto protocolTy = constraint->getSecondType();
+    if (!protocolTy->is<ProtocolType>())
+      return false;
+
+    LLVM_FALLTHROUGH;
+  }
 
   case ConstraintKind::LiteralConformsTo: {
     // Record constraint where protocol requirement originated