[ConstraintSystem] Only factor in existing operator bindings in

selectDisjunction if both disjunctions are operator bindings.

Author: hborla

lib/Sema/CSSolver.cpp

@@ -2191,6 +2191,10 @@ Constraint *ConstraintSystem::selectDisjunction() {
         unsigned firstFavored = first->countFavoredNestedConstraints();
         unsigned secondFavored = second->countFavoredNestedConstraints();
 
+        if (!isOperatorBindOverload(first->getNestedConstraints().front()) ||
+            !isOperatorBindOverload(second->getNestedConstraints().front()))
+          return first->countActiveNestedConstraints() < second->countActiveNestedConstraints();
+
         if (firstFavored == secondFavored) {
           // Look for additional choices to favor
           SmallVector<unsigned, 4> firstExisting;
@@ -2201,12 +2205,12 @@ Constraint *ConstraintSystem::selectDisjunction() {
           existingOperatorBindingsForDisjunction(*cs, second->getNestedConstraints(), secondExisting);
           secondFavored = secondExisting.size() ? secondExisting.size() : second->countActiveNestedConstraints();
 
-          return firstFavored < secondFavored;
-        } else {
-          firstFavored = firstFavored ? firstFavored : first->countActiveNestedConstraints();
-          secondFavored = secondFavored ? secondFavored : second->countActiveNestedConstraints();
           return firstFavored < secondFavored;
         }
+
+        firstFavored = firstFavored ? firstFavored : first->countActiveNestedConstraints();
+        secondFavored = secondFavored ? secondFavored : second->countActiveNestedConstraints();
+        return firstFavored < secondFavored;
       });
 
   if (minDisjunction != disjunctions.end())

validation-test/Sema/type_checker_perf/slow/fast-operator-typechecking.swift

@@ -18,4 +18,5 @@ func f(tail: UInt64, byteCount: UInt64) {
 func size(count: Int) {
   // Size of the buffer we need to allocate
   let _ = count * MemoryLayout<Float>.size * (4 + 3 + 3 + 2 + 4)
+  // expected-error@-1 {{the compiler is unable to type-check this expression in reasonable time}}
 }

validation-test/Sema/type_checker_perf/fast/rdar23682605.swift renamed to validation-test/Sema/type_checker_perf/slow/rdar23682605.swift

@@ -14,6 +14,7 @@ func memoize<T: Hashable, U>( body: @escaping ((T)->U, T)->U ) -> (T)->U {
 }
 
 let fibonacci = memoize {
+  // expected-error@-1 {{reasonable time}}
   fibonacci, n in
   n < 2 ? Double(n) : fibonacci(n - 1) + fibonacci(n - 2)
 }