[CSApply] Use fully qualified locator while coercing array elements

Double/CGFloat implicit conversion expects a full locator
(array-expr + tuple-element <idx>) to find selected overload.

Author: xedin

lib/Sema/CSApply.cpp

@@ -3481,9 +3481,11 @@ namespace {
 
       auto elementType = expr->getElementType();
 
-      for (auto &element : expr->getElements()) {
-        element = coerceToType(element, elementType,
-                               cs.getConstraintLocator(element));
+      for (unsigned i = 0, n = expr->getNumElements(); i != n; ++i) {
+        expr->setElement(
+            i, coerceToType(expr->getElement(i), elementType,
+                            cs.getConstraintLocator(
+                                expr, {LocatorPathElt::TupleElement(i)})));
       }
 
       return expr;

test/Constraints/implicit_double_cgfloat_conversion.swift

@@ -216,3 +216,22 @@ func test_multi_argument_conversion_with_optional(d: Double, cgf: CGFloat) {
 
   test(cgf, d) // Ok (CGFloat -> Double and Double? -> CGFloat?)
 }
+
+func test_array_literal_as_call_argument() {
+  enum E {
+    case test_arr([CGFloat])
+  }
+
+  struct Container {
+    var prop: E
+  }
+
+  struct Point {
+    var x: Double
+    var y: Double
+  }
+
+  func test(cont: inout Container, point: Point) {
+    cont.prop = .test_arr([point.x]) // Ok
+  }
+}