Auto merge of #52761 - toidiu:ak-static-infer-fg, r=nikomatsakis

static infer feature gate

https://github.com/rust-lang/rust/issues/44493

r? @nikomatsakis

src/test/ui/feature-gate-infer_static_outlives_requirements.rs

@@ -0,0 +1,22 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Needs an explicit where clause stating outlives condition. (RFC 2093)
+
+// Type T needs to outlive lifetime 'static.
+struct Foo<U> {
+    bar: Bar<U> //~ ERROR 15:5: 15:16: the parameter type `U` may not live long enough [E0310]
+}
+struct Bar<T: 'static> {
+    x: T,
+}
+
+
+fn main() { }

src/test/ui/feature-gate-infer_static_outlives_requirements.stderr

@@ -0,0 +1,17 @@
+error[E0310]: the parameter type `U` may not live long enough
+  --> $DIR/feature-gate-infer_static_outlives_requirements.rs:15:5
+   |
+LL | struct Foo<U> {
+   |            - help: consider adding an explicit lifetime bound `U: 'static`...
+LL |     bar: Bar<U> //~ ERROR 15:5: 15:16: the parameter type `U` may not live long enough [E0310]
+   |     ^^^^^^^^^^^
+   |
+note: ...so that the type `U` will meet its required lifetime bounds
+  --> $DIR/feature-gate-infer_static_outlives_requirements.rs:15:5
+   |
+LL |     bar: Bar<U> //~ ERROR 15:5: 15:16: the parameter type `U` may not live long enough [E0310]
+   |     ^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0310`.

src/test/ui/rfc-2093-infer-outlives/dont-infer-static.rs

@@ -0,0 +1,29 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-tidy-linelength
+
+#![feature(infer_outlives_requirements)]
+
+/*
+ * We don't infer `T: 'static` outlives relationships by default.
+ * Instead an additional feature gate `infer_static_outlives_requirements`
+ * is required.
+ */
+
+struct Foo<U> {
+    bar: Bar<U> //~ ERROR 22:5: 22:16: the parameter type `U` may not live long enough [E0310]
+}
+struct Bar<T: 'static> {
+    x: T,
+}
+
+fn main() {}
+

src/test/ui/rfc-2093-infer-outlives/dont-infer-static.stderr

@@ -0,0 +1,17 @@
+error[E0310]: the parameter type `U` may not live long enough
+  --> $DIR/dont-infer-static.rs:22:5
+   |
+LL | struct Foo<U> {
+   |            - help: consider adding an explicit lifetime bound `U: 'static`...
+LL |     bar: Bar<U> //~ ERROR 22:5: 22:16: the parameter type `U` may not live long enough [E0310]
+   |     ^^^^^^^^^^^
+   |
+note: ...so that the type `U` will meet its required lifetime bounds
+  --> $DIR/dont-infer-static.rs:22:5
+   |
+LL |     bar: Bar<U> //~ ERROR 22:5: 22:16: the parameter type `U` may not live long enough [E0310]
+   |     ^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0310`.

src/test/ui/rfc-2093-infer-outlives/infer-static.rs

@@ -0,0 +1,24 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(rustc_attrs)]
+#![feature(infer_outlives_requirements)]
+#![feature(infer_static_outlives_requirements)]
+
+#[rustc_outlives]
+struct Foo<U> { //~ ERROR 16:1: 18:2: rustc_outlives
+    bar: Bar<U>
+}
+struct Bar<T: 'static> {
+    x: T,
+}
+
+fn main() {}
+

src/test/ui/rfc-2093-infer-outlives/infer-static.stderr

@@ -0,0 +1,12 @@
+error: rustc_outlives
+  --> $DIR/infer-static.rs:16:1
+   |
+LL | / struct Foo<U> { //~ ERROR 16:1: 18:2: rustc_outlives
+LL | |     bar: Bar<U>
+LL | | }
+   | |_^
+   |
+   = note: U : 'static
+
+error: aborting due to previous error
+