Detect when 'static obligation might come from an impl

Address rust-lang#71341.

src/test/ui/associated-types/cache/project-fn-ret-contravariant.rs

@@ -35,7 +35,7 @@ fn baz<'a,'b>(x: &'a u32, y: &'b u32) -> (&'a u32, &'b u32) {
 
 #[cfg(transmute)] // one instantiations: BAD
 fn baz<'a,'b>(x: &'a u32) -> &'static u32 {
-   bar(foo, x) //[transmute]~ ERROR E0495
+   bar(foo, x) //[transmute]~ ERROR E0759
 }
 
 #[cfg(krisskross)] // two instantiations, mixing and matching: BAD

src/test/ui/associated-types/cache/project-fn-ret-contravariant.transmute.stderr

@@ -1,26 +1,11 @@
-error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
+error[E0759]: cannot infer an appropriate lifetime
   --> $DIR/project-fn-ret-contravariant.rs:38:8
    |
-LL |    bar(foo, x)
-   |        ^^^
-   |
-note: first, the lifetime cannot outlive the lifetime `'a` as defined on the function body at 37:8...
-  --> $DIR/project-fn-ret-contravariant.rs:37:8
-   |
 LL | fn baz<'a,'b>(x: &'a u32) -> &'static u32 {
-   |        ^^
-note: ...so that reference does not outlive borrowed content
-  --> $DIR/project-fn-ret-contravariant.rs:38:13
-   |
-LL |    bar(foo, x)
-   |             ^
-   = note: but, the lifetime must be valid for the static lifetime...
-note: ...so that reference does not outlive borrowed content
-  --> $DIR/project-fn-ret-contravariant.rs:38:4
-   |
+   |                  ------- this data with lifetime `'a`...
 LL |    bar(foo, x)
-   |    ^^^^^^^^^^^
+   |    ----^^^---- ...is captured and required to live as long as `'static` here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0495`.
+For more information about this error, try `rustc --explain E0759`.

src/test/ui/associated-types/cache/project-fn-ret-invariant.rs

@@ -46,7 +46,7 @@ fn baz<'a, 'b>(x: Type<'a>) -> Type<'static> {
     // Cannot instantiate `foo` with any lifetime other than `'a`,
     // since it is provided as input.
 
-    bar(foo, x) //[transmute]~ ERROR E0495
+    bar(foo, x) //[transmute]~ ERROR E0759
 }
 
 #[cfg(krisskross)] // two instantiations, mixing and matching: BAD

src/test/ui/associated-types/cache/project-fn-ret-invariant.transmute.stderr

@@ -1,30 +1,12 @@
-error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
+error[E0759]: cannot infer an appropriate lifetime
   --> $DIR/project-fn-ret-invariant.rs:49:9
    |
-LL |     bar(foo, x)
-   |         ^^^
-   |
-note: first, the lifetime cannot outlive the lifetime `'a` as defined on the function body at 45:8...
-  --> $DIR/project-fn-ret-invariant.rs:45:8
-   |
 LL | fn baz<'a, 'b>(x: Type<'a>) -> Type<'static> {
-   |        ^^
-note: ...so that the expression is assignable
-  --> $DIR/project-fn-ret-invariant.rs:49:14
-   |
-LL |     bar(foo, x)
-   |              ^
-   = note: expected `Type<'_>`
-              found `Type<'a>`
-   = note: but, the lifetime must be valid for the static lifetime...
-note: ...so that the expression is assignable
-  --> $DIR/project-fn-ret-invariant.rs:49:5
-   |
+   |                   -------- this data with lifetime `'a`...
+...
 LL |     bar(foo, x)
-   |     ^^^^^^^^^^^
-   = note: expected `Type<'static>`
-              found `Type<'_>`
+   |     ----^^^---- ...is captured and required to live as long as `'static` here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0495`.
+For more information about this error, try `rustc --explain E0759`.

src/test/ui/impl-header-lifetime-elision/dyn-trait.stderr

@@ -1,30 +1,17 @@
-error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
+error[E0759]: cannot infer an appropriate lifetime
   --> $DIR/dyn-trait.rs:20:16
    |
-LL |     static_val(x);
-   |                ^
-   |
-note: first, the lifetime cannot outlive the lifetime `'a` as defined on the function body at 19:26...
-  --> $DIR/dyn-trait.rs:19:26
-   |
 LL | fn with_dyn_debug_static<'a>(x: Box<dyn Debug + 'a>) {
-   |                          ^^
-note: ...so that the expression is assignable
-  --> $DIR/dyn-trait.rs:20:16
-   |
+   |                                 ------------------- this data with lifetime `'a`...
 LL |     static_val(x);
-   |                ^
-   = note: expected `std::boxed::Box<dyn std::fmt::Debug>`
-              found `std::boxed::Box<(dyn std::fmt::Debug + 'a)>`
-   = note: but, the lifetime must be valid for the static lifetime...
-note: ...so that the types are compatible
+   |                ^ ...is captured here...
+   |
+note: ...and is required to live as long as `'static` here
   --> $DIR/dyn-trait.rs:20:5
    |
 LL |     static_val(x);
    |     ^^^^^^^^^^
-   = note: expected `StaticTrait`
-              found `StaticTrait`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0495`.
+For more information about this error, try `rustc --explain E0759`.

src/test/ui/nll/user-annotations/constant-in-expr-inherent-1.stderr

@@ -1,28 +1,11 @@
-error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
+error[E0759]: cannot infer an appropriate lifetime
   --> $DIR/constant-in-expr-inherent-1.rs:8:5
    |
-LL |     <Foo<'a>>::C
-   |     ^^^^^^^^^^^^
-   |
-note: first, the lifetime cannot outlive the lifetime `'a` as defined on the function body at 7:8...
-  --> $DIR/constant-in-expr-inherent-1.rs:7:8
-   |
 LL | fn foo<'a>(_: &'a u32) -> &'static u32 {
-   |        ^^
-note: ...so that the types are compatible
-  --> $DIR/constant-in-expr-inherent-1.rs:8:5
-   |
-LL |     <Foo<'a>>::C
-   |     ^^^^^^^^^^^^
-   = note: expected `Foo<'_>`
-              found `Foo<'a>`
-   = note: but, the lifetime must be valid for the static lifetime...
-note: ...so that reference does not outlive borrowed content
-  --> $DIR/constant-in-expr-inherent-1.rs:8:5
-   |
+   |               ------- this data with lifetime `'a`...
 LL |     <Foo<'a>>::C
-   |     ^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^ ...is captured and required to live as long as `'static` here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0495`.
+For more information about this error, try `rustc --explain E0759`.

src/test/ui/regions/regions-addr-of-self.stderr

@@ -1,29 +1,11 @@
-error[E0495]: cannot infer an appropriate lifetime for borrow expression due to conflicting requirements
+error[E0759]: cannot infer an appropriate lifetime
   --> $DIR/regions-addr-of-self.rs:7:37
    |
+LL |     pub fn chase_cat(&mut self) {
+   |                      --------- this data with an anonymous lifetime `'_`...
 LL |         let p: &'static mut usize = &mut self.cats_chased;
-   |                                     ^^^^^^^^^^^^^^^^^^^^^
-   |
-note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the method body at 6:5...
-  --> $DIR/regions-addr-of-self.rs:6:5
-   |
-LL | /     pub fn chase_cat(&mut self) {
-LL | |         let p: &'static mut usize = &mut self.cats_chased;
-LL | |         *p += 1;
-LL | |     }
-   | |_____^
-note: ...so that reference does not outlive borrowed content
-  --> $DIR/regions-addr-of-self.rs:7:37
-   |
-LL |         let p: &'static mut usize = &mut self.cats_chased;
-   |                                     ^^^^^^^^^^^^^^^^^^^^^
-   = note: but, the lifetime must be valid for the static lifetime...
-note: ...so that reference does not outlive borrowed content
-  --> $DIR/regions-addr-of-self.rs:7:37
-   |
-LL |         let p: &'static mut usize = &mut self.cats_chased;
-   |                                     ^^^^^^^^^^^^^^^^^^^^^
+   |                                     ^^^^^^^^^^^^^^^^^^^^^ ...is captured and required to live as long as `'static` here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0495`.
+For more information about this error, try `rustc --explain E0759`.

src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound-without-suggestion.rs

@@ -0,0 +1,14 @@
+trait OtherTrait<'a> {}
+impl<'a> OtherTrait<'a> for &'a () {}
+
+trait ObjectTrait {}
+
+impl dyn ObjectTrait {
+    fn use_self(&self) -> &() { panic!() }
+}
+
+fn use_it<'a>(val: &'a dyn ObjectTrait) -> impl OtherTrait<'a> + 'a {
+    val.use_self() //~ ERROR mismatched types
+}
+
+fn main() {}

src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound-without-suggestion.stderr

@@ -0,0 +1,18 @@
+error[E0308]: mismatched types
+  --> $DIR/impl-on-dyn-trait-with-implicit-static-bound-without-suggestion.rs:11:9
+   |
+LL |     val.use_self()
+   |         ^^^^^^^^ lifetime mismatch
+   |
+   = note: expected reference `&(dyn ObjectTrait + 'static)`
+              found reference `&(dyn ObjectTrait + 'a)`
+note: the lifetime `'a` as defined on the function body at 10:11...
+  --> $DIR/impl-on-dyn-trait-with-implicit-static-bound-without-suggestion.rs:10:11
+   |
+LL | fn use_it<'a>(val: &'a dyn ObjectTrait) -> impl OtherTrait<'a> + 'a {
+   |           ^^
+   = note: ...does not necessarily outlive the static lifetime
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound.fixed

@@ -0,0 +1,37 @@
+// run-rustfix
+#![allow(dead_code)]
+
+mod foo {
+    trait OtherTrait<'a> {}
+    impl<'a> OtherTrait<'a> for &'a () {}
+
+    trait ObjectTrait {}
+    trait MyTrait {
+        fn use_self(&self) -> &();
+    }
+
+    impl MyTrait for dyn ObjectTrait + '_ {
+        fn use_self(&self) -> &() { panic!() }
+    }
+
+    fn use_it<'a>(val: &'a dyn ObjectTrait) -> impl OtherTrait<'a> + 'a {
+        val.use_self() //~ ERROR cannot infer an appropriate lifetime
+    }
+}
+
+mod bar {
+    trait ObjectTrait {}
+    trait MyTrait {
+        fn use_self(&self) -> &();
+    }
+
+    impl MyTrait for dyn ObjectTrait + '_ {
+        fn use_self(&self) -> &() { panic!() }
+    }
+
+    fn use_it<'a>(val: &'a dyn ObjectTrait) -> &'a () {
+        val.use_self() //~ ERROR cannot infer an appropriate lifetime
+    }
+}
+
+fn main() {}

src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound.rs

@@ -0,0 +1,37 @@
+// run-rustfix
+#![allow(dead_code)]
+
+mod foo {
+    trait OtherTrait<'a> {}
+    impl<'a> OtherTrait<'a> for &'a () {}
+
+    trait ObjectTrait {}
+    trait MyTrait {
+        fn use_self(&self) -> &();
+    }
+
+    impl MyTrait for dyn ObjectTrait {
+        fn use_self(&self) -> &() { panic!() }
+    }
+
+    fn use_it<'a>(val: &'a dyn ObjectTrait) -> impl OtherTrait<'a> + 'a {
+        val.use_self() //~ ERROR cannot infer an appropriate lifetime
+    }
+}
+
+mod bar {
+    trait ObjectTrait {}
+    trait MyTrait {
+        fn use_self(&self) -> &();
+    }
+
+    impl MyTrait for dyn ObjectTrait {
+        fn use_self(&self) -> &() { panic!() }
+    }
+
+    fn use_it<'a>(val: &'a dyn ObjectTrait) -> &'a () {
+        val.use_self() //~ ERROR cannot infer an appropriate lifetime
+    }
+}
+
+fn main() {}

src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound.stderr

@@ -0,0 +1,29 @@
+error[E0759]: cannot infer an appropriate lifetime
+  --> $DIR/impl-on-dyn-trait-with-implicit-static-bound.rs:18:13
+   |
+LL |     fn use_it<'a>(val: &'a dyn ObjectTrait) -> impl OtherTrait<'a> + 'a {
+   |                        ------------------- this data with lifetime `'a`...
+LL |         val.use_self()
+   |             ^^^^^^^^ ...is captured and required to live as long as `'static` here
+   |
+help: this `impl` introduces an implicit `'static` requirement, consider changing it
+   |
+LL |     impl MyTrait for dyn ObjectTrait + '_ {
+   |                                      ^^^^
+
+error[E0759]: cannot infer an appropriate lifetime
+  --> $DIR/impl-on-dyn-trait-with-implicit-static-bound.rs:33:13
+   |
+LL |     fn use_it<'a>(val: &'a dyn ObjectTrait) -> &'a () {
+   |                        ------------------- this data with lifetime `'a`...
+LL |         val.use_self()
+   |             ^^^^^^^^ ...is captured and required to live as long as `'static` here
+   |
+help: this `impl` introduces an implicit `'static` requirement, consider changing it
+   |
+LL |     impl MyTrait for dyn ObjectTrait + '_ {
+   |                                      ^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0759`.