[CS] Sink closure attribute/param checking into applySolution

The cases where CSApply fails should be fairly
limited these days, and there doesn't seem to be
any reason we shouldn't run these on failure anyway.

Author: hamishknight

lib/Sema/CSApply.cpp

@@ -8908,14 +8908,8 @@ namespace {
     /// \returns true if an error occurred.
     bool rewriteFunction(AnyFunctionRef fn) {
       switch (Rewriter.cs.applySolution(fn, *this)) {
-      case SolutionApplicationToFunctionResult::Success: {
-        if (auto closure =
-                dyn_cast_or_null<ClosureExpr>(fn.getAbstractClosureExpr())) {
-          TypeChecker::checkClosureAttributes(closure);
-          TypeChecker::checkParameterList(closure->getParameters(), closure);
-        }
+      case SolutionApplicationToFunctionResult::Success:
         return false;
-      }
 
       case SolutionApplicationToFunctionResult::Failure:
         return true;

lib/Sema/CSSyntacticElement.cpp

@@ -2573,6 +2573,9 @@ ConstraintSystem::applySolution(AnyFunctionRef fn,
     }
 
     applySolutionToClosurePropertyWrappers(closure, solution);
+
+    TypeChecker::checkClosureAttributes(closure);
+    TypeChecker::checkParameterList(closure->getParameters(), closure);
   }
 
   // Enter the context of the function before performing any additional