From e38a2b9a0820ec060e4c51c0f325d95234f4544b Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Thu, 6 Mar 2014 00:18:41 +0000
Subject: [PATCH] Discourage constraint systems that use more unchecked forces.

This is in preparation for a change that allows unchecked-optional
values to be implicitly forced in all contexts.

Swift SVN r14704
---
 lib/Sema/CSSimplify.cpp     | 1 +
 lib/Sema/ConstraintSystem.h | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/Sema/CSSimplify.cpp b/lib/Sema/CSSimplify.cpp
index 386a662d1f7e2..e5f27db2385ca 100644
--- a/lib/Sema/CSSimplify.cpp
+++ b/lib/Sema/CSSimplify.cpp
@@ -1360,6 +1360,7 @@ ConstraintSystem::simplifyMemberConstraint(const Constraint &constraint) {
 
   // Try to look through UncheckedOptional<T>; the result is always an r-value.
   if (auto objTy = lookThroughUncheckedOptionalType(baseObjTy)) {
+    increaseScore(SK_UncheckedForce);
     baseTy = baseObjTy = objTy;
   }
 
diff --git a/lib/Sema/ConstraintSystem.h b/lib/Sema/ConstraintSystem.h
index f6268dff68771..8d3463d7af302 100644
--- a/lib/Sema/ConstraintSystem.h
+++ b/lib/Sema/ConstraintSystem.h
@@ -584,6 +584,8 @@ struct SelectedOverload {
 enum ScoreKind {
   // These values are used as indices into a Score value.
 
+  /// An implicit force of an unchecked optional value.
+  SK_UncheckedForce,
   /// A user-defined conversion.
   SK_UserConversion,
   /// A non-trivial function conversion.
@@ -593,7 +595,7 @@ enum ScoreKind {
 };
 
 /// The number of score kinds.
-const unsigned NumScoreKinds = 3;
+const unsigned NumScoreKinds = 4;
 
 /// Describes the fixed score of a solution to the constraint system.
 struct Score {