[tests] Adding regression tests and for unwrapping base on key path application

Author: LucianoPAlmeida

test/Constraints/keypath.swift

@@ -152,3 +152,30 @@ func fSR11184_O(_ c: SR11184!, _ kp: ReferenceWritableKeyPath<SR11184, String?>,
   c![keyPath: kp] = str // OK
   c?[keyPath: kp] = str // OK
 }
+
+class KeyPathBase {}
+class KeyPathBaseSubtype: KeyPathBase {}
+class AnotherBase {}
+class AnotherComposeBase {
+  var member: KeyPathBase?
+}
+
+func key_path_root_mismatch<T>(_ base: KeyPathBase?, subBase: KeyPathBaseSubtype?, _ abase: AnotherComposeBase,
+                               _ kp: KeyPath<KeyPathBase, T>, _ kpa: KeyPath<AnotherBase, T>) {
+  let _ : T = base[keyPath: kp] // expected-error {{value of optional type 'KeyPathBase?' must be unwrapped to a value of type 'KeyPathBase'}}
+  // expected-note@-1 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}} {{19-19=!}}
+  // expected-note@-2 {{use '?' to access key path subscript only for non-'nil' base values}} {{19-19=?}}
+  let _ : T = base[keyPath: kpa] // expected-error {{key path with root type 'AnotherBase' cannot be applied to a base of type 'KeyPathBase?'}}
+
+  // Chained root mismatch
+  let _ : T = abase.member[keyPath: kp] // expected-error {{value of optional type 'KeyPathBase?' must be unwrapped to a value of type 'KeyPathBase'}}
+  // expected-note@-1 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}} {{27-27=!}}
+  // expected-note@-2 {{use '?' to access key path subscript only for non-'nil' base values}} {{27-27=?}}
+  let _ : T = abase.member[keyPath: kpa] // expected-error {{key path with root type 'AnotherBase' cannot be applied to a base of type 'KeyPathBase?'}}
+
+  let _ : T = subBase[keyPath: kp] // expected-error {{value of optional type 'KeyPathBaseSubtype?' must be unwrapped to a value of type 'KeyPathBaseSubtype'}}
+  // expected-note@-1 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}} {{22-22=!}}
+  // expected-note@-2 {{use '?' to access key path subscript only for non-'nil' base values}} {{22-22=?}}
+  let _ : T = subBase[keyPath: kpa] // expected-error {{key path with root type 'AnotherBase' cannot be applied to a base of type 'KeyPathBaseSubtype?'}}
+
+}

test/expr/unary/keypath/keypath.swift

@@ -452,20 +452,24 @@ func testKeyPathSubscriptExistentialBase(concreteBase: inout B,
   _ = concreteBase[keyPath: rkp]
   _ = concreteBase[keyPath: pkp]
 
-  concreteBase[keyPath: kp] = s // expected-error{{}}
-  concreteBase[keyPath: wkp] = s // expected-error{{}}
+  concreteBase[keyPath: kp] = s // expected-error {{cannot assign through subscript: 'kp' is a read-only key path}}
+  concreteBase[keyPath: wkp] = s // expected-error {{key path with root type 'P' cannot be applied to a base of type 'B'}}
   concreteBase[keyPath: rkp] = s
-  concreteBase[keyPath: pkp] = s // expected-error{{}}
+  // TODO(diagnostics): Improve this diagnostic message because concreteBase is mutable, the problem is related to assign 
+  // through PartialKeyPath.
+  concreteBase[keyPath: pkp] = s // expected-error {{cannot assign through subscript: 'concreteBase' is immutable}}
 
   _ = existentialBase[keyPath: kp]
   _ = existentialBase[keyPath: wkp]
   _ = existentialBase[keyPath: rkp]
   _ = existentialBase[keyPath: pkp]
 
-  existentialBase[keyPath: kp] = s // expected-error{{}}
+  existentialBase[keyPath: kp] = s // expected-error {{cannot assign through subscript: 'kp' is a read-only key path}}
   existentialBase[keyPath: wkp] = s
   existentialBase[keyPath: rkp] = s
-  existentialBase[keyPath: pkp] = s // expected-error{{}}
+  // TODO(diagnostics): Improve this diagnostic message because existentialBase is mutable, the problem is related to assign 
+  // through PartialKeyPath.
+  existentialBase[keyPath: pkp] = s // expected-error {{cannot assign through subscript: 'existentialBase' is immutable}}
 }
 
 struct AA {