[ConstraintSystem] Don't increase the score for unapplied function references

if the expression is an argument to `#selector`.

For `#selector` arguments, functions and properties are syntactically distinct
with the getter/setter label, so the solver should not unconditionally prefer
properties to unapplied functions. A better fix for this is to port over the
`#selector` diagnostics from CSApply, and not attempt invalid disjunction choices
based on the selector kind on the valid code path.

Author: hborla

lib/Sema/CSGen.cpp

@@ -3464,7 +3464,8 @@ namespace {
       // Note that the subexpression of a #selector expression is
       // unevaluated.
       if (auto sel = dyn_cast<ObjCSelectorExpr>(expr)) {
-        CG.getConstraintSystem().UnevaluatedRootExprs.insert(sel->getSubExpr());
+        auto *subExpr = sel->getSubExpr()->getSemanticsProvidingExpr();
+        CG.getConstraintSystem().UnevaluatedRootExprs.insert(subExpr);
       }
 
       // Check an objc key-path expression, which fills in its semantic

lib/Sema/ConstraintSystem.cpp

@@ -2916,7 +2916,13 @@ void ConstraintSystem::resolveOverload(ConstraintLocator *locator,
     }
 
     if (isa<AbstractFunctionDecl>(decl) || isa<TypeDecl>(decl)) {
-      if (choice.getFunctionRefKind() == FunctionRefKind::Unapplied) {
+      auto anchor = locator->getAnchor();
+      // TODO: Instead of not increasing the score for arguments to #selector,
+      // a better fix for this is to port over the #selector diagnostics from
+      // CSApply to constraint fixes, and not attempt invalid disjunction
+      // choices based on the selector kind on the valid code path.
+      if (choice.getFunctionRefKind() == FunctionRefKind::Unapplied &&
+          !UnevaluatedRootExprs.contains(getAsExpr(anchor))) {
         increaseScore(SK_UnappliedFunction);
       }
     }