Add tests for basic LifetimeDependence requirements

Test each basic case that requires LifetimeDependences,
first without enabling the LifetimeDependence feature,
then without specifying the kind of dependence.

Author: atrick

test/Sema/lifetime_depend_noattr.swift

@@ -0,0 +1,34 @@
+// RUN: %target-swift-frontend %s -emit-sil \
+// RUN:   -o /dev/null \
+// RUN:   -verify \
+// RUN:   -sil-verify-all \
+// RUN:   -disable-availability-checking \
+// RUN:   -module-name test \
+// RUN:   -enable-experimental-feature LifetimeDependence
+
+// REQUIRES: swift_feature_LifetimeDependence
+
+// These tests complement lifetime_depend_nofeature.swift. If you add a test here, add one there.
+ 
+// Check that missing lifetime dependencies are diagnosed. Enabling LifetimeDependencies will issue more detailed
+// diagnostics.
+
+// Allow empty initialization.
+struct EmptyNonEscapable: ~Escapable {} // OK - no dependence
+
+// Don't allow non-Escapable return values.
+func neReturn(span: RawSpan) -> RawSpan { span } // expected-error{{cannot infer the lifetime dependence scope on a function with a ~Escapable parameter, specify '@lifetime(borrow span)' or '@lifetime(copy span)'}}
+
+func neInout(span: inout RawSpan) {} // OK - inferred
+
+struct S {
+  func neReturn(span: RawSpan) -> RawSpan { span } // expected-error{{a method with a ~Escapable result requires '@lifetime(...)}}
+
+  func neInout(span: inout RawSpan) {} // OK - inferred
+}
+
+class C {
+  func neReturn(span: RawSpan) -> RawSpan { span } // expected-error{{a method with a ~Escapable result requires '@lifetime(...)'}}
+
+  func neInout(span: inout RawSpan) {} // OK - inferred
+}

test/Sema/lifetime_depend_nofeature.swift

@@ -0,0 +1,30 @@
+// RUN: %target-swift-frontend %s -emit-sil \
+// RUN:   -o /dev/null \
+// RUN:   -verify \
+// RUN:   -sil-verify-all \
+// RUN:   -disable-availability-checking \
+// RUN:   -module-name test
+
+// These tests complement lifetime_depend_noattr.swift. If you add a test here, add one there.
+
+// Check that functions that require lifetime dependence are prohibited without the flag.
+
+// Don't allow empty initialization.
+struct EmptyNonEscapable: ~Escapable {} // expected-error{{an implicit initializer with a ~Escapable result requires '-enable-experimental-feature LifetimeDependence'}}
+
+// Don't allow non-Escapable return values.
+func neReturn(span: RawSpan) -> RawSpan { span } // expected-error{{a function with a ~Escapable result requires '-enable-experimental-feature LifetimeDependence'}}
+
+func neInout(span: inout RawSpan) {} // expected-error{{a function with a ~Escapable 'inout' parameter requires '-enable-experimental-feature LifetimeDependence'}}
+
+struct S {
+  func neReturn(span: RawSpan) -> RawSpan { span } // expected-error{{a method with a ~Escapable result requires '-enable-experimental-feature LifetimeDependence'}}
+
+  func neInout(span: inout RawSpan) {} // expected-error{{a method with a ~Escapable 'inout' parameter requires '-enable-experimental-feature LifetimeDependence'}}
+}
+
+class C {
+  func neReturn(span: RawSpan) -> RawSpan { span } // expected-error{{a method with a ~Escapable result requires '-enable-experimental-feature LifetimeDependence'}}
+
+  func neInout(span: inout RawSpan) {} // expected-error{{a method with a ~Escapable 'inout' parameter requires '-enable-experimental-feature LifetimeDependence'}}
+}