feature gate for inferring 'static lifetimes
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@ -27,7 +27,7 @@ pub fn insert_outlives_predicate<'tcx>(
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) {
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) {
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// If the `'a` region is bound within the field type itself, we
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// If the `'a` region is bound within the field type itself, we
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// don't want to propagate this constraint to the header.
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// don't want to propagate this constraint to the header.
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if !is_free_region(outlived_region) {
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if !is_free_region(tcx, outlived_region) {
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return;
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return;
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}
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}
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@ -120,7 +120,7 @@ pub fn insert_outlives_predicate<'tcx>(
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}
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}
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UnpackedKind::Lifetime(r) => {
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UnpackedKind::Lifetime(r) => {
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if !is_free_region(r) {
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if !is_free_region(tcx, r) {
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return;
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return;
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}
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}
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required_predicates.insert(ty::OutlivesPredicate(kind, outlived_region));
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required_predicates.insert(ty::OutlivesPredicate(kind, outlived_region));
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@ -128,19 +128,36 @@ pub fn insert_outlives_predicate<'tcx>(
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}
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}
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}
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}
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fn is_free_region(region: Region<'_>) -> bool {
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fn is_free_region<'tcx>(tcx: TyCtxt<'_, 'tcx, 'tcx>, region: Region<'_>) -> bool {
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// First, screen for regions that might appear in a type header.
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// First, screen for regions that might appear in a type header.
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match region {
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match region {
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// *These* correspond to `T: 'a` relationships where `'a` is
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// These correspond to `T: 'a` relationships:
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// either declared on the type or `'static`:
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//
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//
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// struct Foo<'a, T> {
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// struct Foo<'a, T> {
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// field: &'a T, // this would generate a ReEarlyBound referencing `'a`
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// field: &'a T, // this would generate a ReEarlyBound referencing `'a`
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// field2: &'static T, // this would generate a ReStatic
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// }
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// }
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//
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//
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// We care about these, so fall through.
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// We care about these, so fall through.
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RegionKind::ReStatic | RegionKind::ReEarlyBound(_) => true,
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RegionKind::ReEarlyBound(_) => true,
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// These correspond to `T: 'static` relationships which can be
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// rather surprising. We are therefore putting this behind a
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// feature flag:
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//
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// struct Foo<'a, T> {
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// field: &'static T, // this would generate a ReStatic
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// }
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RegionKind::ReStatic => {
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if tcx
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.sess
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.features_untracked()
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.infer_static_outlives_requirements
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{
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true
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} else {
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false
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}
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}
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// Late-bound regions can appear in `fn` types:
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// Late-bound regions can appear in `fn` types:
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//
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//
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@ -396,6 +396,9 @@ declare_features! (
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// Infer outlives requirements; RFC 2093
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// Infer outlives requirements; RFC 2093
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(active, infer_outlives_requirements, "1.26.0", Some(44493), None),
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(active, infer_outlives_requirements, "1.26.0", Some(44493), None),
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// Infer outlives requirements; RFC 2093
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(active, infer_static_outlives_requirements, "1.26.0", Some(44493), None),
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// Multiple patterns with `|` in `if let` and `while let`
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// Multiple patterns with `|` in `if let` and `while let`
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(active, if_while_or_patterns, "1.26.0", Some(48215), None),
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(active, if_while_or_patterns, "1.26.0", Some(48215), None),
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@ -1057,6 +1060,12 @@ pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeG
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"infer outlives requirements is an experimental feature",
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"infer outlives requirements is an experimental feature",
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cfg_fn!(infer_outlives_requirements))),
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cfg_fn!(infer_outlives_requirements))),
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// RFC #2093
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("infer_static_outlives_requirements", Normal, Gated(Stability::Unstable,
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"infer_static_outlives_requirements",
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"infer 'static lifetime requirements",
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cfg_fn!(infer_static_outlives_requirements))),
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// RFC 2070
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// RFC 2070
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("panic_implementation", Normal, Gated(Stability::Unstable,
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("panic_implementation", Normal, Gated(Stability::Unstable,
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"panic_implementation",
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"panic_implementation",
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@ -0,0 +1,23 @@
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// ignore-tidy-linelength
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#![feature(infer_outlives_requirements)]
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struct Foo<U> {
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bar: Bar<U> //~ ERROR 16:5: 16:16: the parameter type `U` may not live long enough [E0310]
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}
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struct Bar<T: 'static> {
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x: T,
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}
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fn main() {}
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@ -0,0 +1,17 @@
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error[E0310]: the parameter type `U` may not live long enough
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--> $DIR/dont-infer-static.rs:16:5
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LL | struct Foo<U> {
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| - help: consider adding an explicit lifetime bound `U: 'static`...
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LL | bar: Bar<U> //~ ERROR 16:5: 16:16: the parameter type `U` may not live long enough [E0310]
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| ^^^^^^^^^^^
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note: ...so that the type `U` will meet its required lifetime bounds
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--> $DIR/dont-infer-static.rs:16:5
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LL | bar: Bar<U> //~ ERROR 16:5: 16:16: the parameter type `U` may not live long enough [E0310]
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| ^^^^^^^^^^^
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0310`.
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@ -0,0 +1,25 @@
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#![feature(rustc_attrs)]
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#![feature(infer_outlives_requirements)]
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#![feature(infer_static_outlives_requirements)]
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#[rustc_outlives]
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struct Foo<U> { //~ ERROR 16:1: 18:2: rustc_outlives
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bar: Bar<U>
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}
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struct Bar<T: 'static> {
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x: T,
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}
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fn main() {}
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@ -0,0 +1,12 @@
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error: rustc_outlives
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--> $DIR/infer-static.rs:16:1
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LL | / struct Foo<U> { //~ ERROR 16:1: 18:2: rustc_outlives
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LL | | bar: Bar<U>
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LL | | }
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| |_^
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= note: U : 'static
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error: aborting due to previous error
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