Merge pull request #26712 from gregomni/sr-11234

[CSGen] Coerce key path index expr to handle upcast correctly.

Author: gregomni

lib/Sema/CSApply.cpp

@@ -1285,7 +1285,10 @@ namespace {
         } else {
           auto keyPathBGT = keyPathTy->castTo<BoundGenericType>();
           baseTy = keyPathBGT->getGenericArgs()[0];
-          
+
+          // Coerce the index to the key path's type
+          indexKP = coerceToType(indexKP, keyPathTy, locator);
+
           // Coerce the base to the key path's expected base type.
           if (!baseTy->isEqual(cs.getType(base)->getRValueType()))
             base = coerceToType(base, baseTy, locator);

test/Constraints/keypath.swift

@@ -51,3 +51,11 @@ func testFunc() {
   let f = \S.i
   let _: (S) -> Int = f // expected-error {{cannot convert value of type 'KeyPath<S, Int>' to specified type '(S) -> Int'}}
 }
+
+// SR-11234
+public extension Array {
+    func sorted<C: Comparable, K: KeyPath<Element, C>>(by keyPath: K) -> Array<Element> {
+        let sortedA = self.sorted(by: { $0[keyPath: keyPath] < $1[keyPath: keyPath] })
+        return sortedA
+    }
+}