Auto merge of #92123 - m-ou-se:thread-local-cell-methods, r=joshtriplett

Implement RFC 3184 - thread local cell methods

This implements [RFC 3184](https://github.com/rust-lang/rfcs/pull/3184), with `@danielhenrymantilla's` [suggestion](https://github.com/rust-lang/rfcs/pull/3184#issuecomment-965773616) for the `with_` method names.

Tracking issue: https://github.com/rust-lang/rust/issues/92122

5 files changed, 120 insertions, 63 deletions

diff --git a/src/test/ui/suggestions/missing-lifetime-specifier.rs b/src/test/ui/suggestions/missing-lifetime-specifier.rs
index 4aaac2d95d4..ce847c86bed 100644
--- a/src/test/ui/suggestions/missing-lifetime-specifier.rs
+++ b/src/test/ui/suggestions/missing-lifetime-specifier.rs
@@ -45,6 +45,7 @@ thread_local! {
     //~| ERROR this union takes 2 lifetime arguments but 1 lifetime argument was supplied
     //~| ERROR this union takes 2 lifetime arguments but 1 lifetime argument was supplied
     //~| ERROR this union takes 2 lifetime arguments but 1 lifetime argument was supplied
+    //~| ERROR this union takes 2 lifetime arguments but 1 lifetime argument was supplied
 }
 thread_local! {
     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, i32>>>>> = RefCell::new(HashMap::new());
@@ -52,6 +53,7 @@ thread_local! {
     //~| ERROR this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
     //~| ERROR this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
     //~| ERROR this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
+    //~| ERROR this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
     //~| ERROR missing lifetime
     //~| ERROR missing lifetime
 }
diff --git a/src/test/ui/suggestions/missing-lifetime-specifier.stderr b/src/test/ui/suggestions/missing-lifetime-specifier.stderr
index bf546384124..b04ea1c9158 100644
--- a/src/test/ui/suggestions/missing-lifetime-specifier.stderr
+++ b/src/test/ui/suggestions/missing-lifetime-specifier.stderr
@@ -13,14 +13,15 @@ LL |     static a: RefCell<HashMap<i32, Vec<Vec<Foo<'static, 'static>>>>> = RefC
 error[E0106]: missing lifetime specifiers
   --> $DIR/missing-lifetime-specifier.rs:18:44
    |
-LL |     static a: RefCell<HashMap<i32, Vec<Vec<Foo>>>> = RefCell::new(HashMap::new());
-   |                                            ^^^ expected 2 lifetime parameters
-   |
-   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
-help: consider using the `'static` lifetime
-   |
-LL |     static a: RefCell<HashMap<i32, Vec<Vec<Foo<'static, 'static>>>>> = RefCell::new(HashMap::new());
-   |                                            ~~~~~~~~~~~~~~~~~~~~~
+LL | / thread_local! {
+LL | |     static a: RefCell<HashMap<i32, Vec<Vec<Foo>>>> = RefCell::new(HashMap::new());
+   | |                                            ^^^ expected 2 lifetime parameters
+LL | |
+LL | |
+LL | | }
+   | |_-
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say which one of `init`'s 3 lifetimes it is borrowed from
 
 error[E0106]: missing lifetime specifier
   --> $DIR/missing-lifetime-specifier.rs:23:44
@@ -49,26 +50,32 @@ LL |     static b: RefCell<HashMap<i32, Vec<Vec<&Bar<'static, 'static>>>>> = Ref
 error[E0106]: missing lifetime specifier
   --> $DIR/missing-lifetime-specifier.rs:23:44
    |
-LL |     static b: RefCell<HashMap<i32, Vec<Vec<&Bar>>>> = RefCell::new(HashMap::new());
-   |                                            ^ expected named lifetime parameter
-   |
-   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
-help: consider using the `'static` lifetime
-   |
-LL |     static b: RefCell<HashMap<i32, Vec<Vec<&'static Bar>>>> = RefCell::new(HashMap::new());
-   |                                            ~~~~~~~~
+LL | / thread_local! {
+LL | |     static b: RefCell<HashMap<i32, Vec<Vec<&Bar>>>> = RefCell::new(HashMap::new());
+   | |                                            ^ expected named lifetime parameter
+LL | |
+LL | |
+LL | |
+LL | |
+LL | | }
+   | |_-
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say which one of `init`'s 4 lifetimes it is borrowed from
 
 error[E0106]: missing lifetime specifiers
   --> $DIR/missing-lifetime-specifier.rs:23:45
    |
-LL |     static b: RefCell<HashMap<i32, Vec<Vec<&Bar>>>> = RefCell::new(HashMap::new());
-   |                                             ^^^ expected 2 lifetime parameters
-   |
-   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
-help: consider using the `'static` lifetime
-   |
-LL |     static b: RefCell<HashMap<i32, Vec<Vec<&Bar<'static, 'static>>>>> = RefCell::new(HashMap::new());
-   |                                             ~~~~~~~~~~~~~~~~~~~~~
+LL | / thread_local! {
+LL | |     static b: RefCell<HashMap<i32, Vec<Vec<&Bar>>>> = RefCell::new(HashMap::new());
+   | |                                             ^^^ expected 2 lifetime parameters
+LL | |
+LL | |
+LL | |
+LL | |
+LL | | }
+   | |_-
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say which one of `init`'s 4 lifetimes it is borrowed from
 
 error[E0106]: missing lifetime specifiers
   --> $DIR/missing-lifetime-specifier.rs:30:48
@@ -85,14 +92,15 @@ LL |     static c: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'static, i32>>>>> =
 error[E0106]: missing lifetime specifiers
   --> $DIR/missing-lifetime-specifier.rs:30:48
    |
-LL |     static c: RefCell<HashMap<i32, Vec<Vec<Qux<i32>>>>> = RefCell::new(HashMap::new());
-   |                                                ^ expected 2 lifetime parameters
-   |
-   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
-help: consider using the `'static` lifetime
+LL | / thread_local! {
+LL | |     static c: RefCell<HashMap<i32, Vec<Vec<Qux<i32>>>>> = RefCell::new(HashMap::new());
+   | |                                                ^ expected 2 lifetime parameters
+LL | |
+LL | |
+LL | | }
+   | |_-
    |
-LL |     static c: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                +++++++++++++++++
+   = help: this function's return type contains a borrowed value, but the signature does not say which one of `init`'s 3 lifetimes it is borrowed from
 
 error[E0106]: missing lifetime specifier
   --> $DIR/missing-lifetime-specifier.rs:35:44
@@ -121,26 +129,50 @@ LL |     static d: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'static, i32>>>>>
 error[E0106]: missing lifetime specifier
   --> $DIR/missing-lifetime-specifier.rs:35:44
    |
-LL |     static d: RefCell<HashMap<i32, Vec<Vec<&Tar<i32>>>>> = RefCell::new(HashMap::new());
-   |                                            ^ expected named lifetime parameter
-   |
-   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
-help: consider using the `'static` lifetime
-   |
-LL |     static d: RefCell<HashMap<i32, Vec<Vec<&'static Tar<i32>>>>> = RefCell::new(HashMap::new());
-   |                                            ~~~~~~~~
+LL | / thread_local! {
+LL | |     static d: RefCell<HashMap<i32, Vec<Vec<&Tar<i32>>>>> = RefCell::new(HashMap::new());
+   | |                                            ^ expected named lifetime parameter
+LL | |
+LL | |
+LL | |
+LL | |
+LL | | }
+   | |_-
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say which one of `init`'s 4 lifetimes it is borrowed from
 
 error[E0106]: missing lifetime specifiers
   --> $DIR/missing-lifetime-specifier.rs:35:49
    |
-LL |     static d: RefCell<HashMap<i32, Vec<Vec<&Tar<i32>>>>> = RefCell::new(HashMap::new());
-   |                                                 ^ expected 2 lifetime parameters
+LL | / thread_local! {
+LL | |     static d: RefCell<HashMap<i32, Vec<Vec<&Tar<i32>>>>> = RefCell::new(HashMap::new());
+   | |                                                 ^ expected 2 lifetime parameters
+LL | |
+LL | |
+LL | |
+LL | |
+LL | | }
+   | |_-
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say which one of `init`'s 4 lifetimes it is borrowed from
+
+error[E0107]: this union takes 2 lifetime arguments but 1 lifetime argument was supplied
+  --> $DIR/missing-lifetime-specifier.rs:43:44
    |
-   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
-help: consider using the `'static` lifetime
+LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                            ^^^ ------- supplied 1 lifetime argument
+   |                                            |
+   |                                            expected 2 lifetime arguments
    |
-LL |     static d: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                 +++++++++++++++++
+note: union defined here, with 2 lifetime parameters: `'t`, `'k`
+  --> $DIR/missing-lifetime-specifier.rs:11:11
+   |
+LL | pub union Qux<'t, 'k, I> {
+   |           ^^^ --  --
+help: add missing lifetime argument
+   |
+LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, '_, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                       ++++
 
 error[E0107]: this union takes 2 lifetime arguments but 1 lifetime argument was supplied
   --> $DIR/missing-lifetime-specifier.rs:43:44
@@ -157,7 +189,7 @@ LL | pub union Qux<'t, 'k, I> {
    |           ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, '_, i32>>>>> = RefCell::new(HashMap::new());
+LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'k, i32>>>>> = RefCell::new(HashMap::new());
    |                                                       ++++
 
 error[E0107]: this union takes 2 lifetime arguments but 1 lifetime argument was supplied
@@ -215,7 +247,7 @@ LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, '_, i32>>>>> = RefC
    |                                                       ++++
 
 error[E0107]: this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
-  --> $DIR/missing-lifetime-specifier.rs:50:45
+  --> $DIR/missing-lifetime-specifier.rs:51:45
    |
 LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, i32>>>>> = RefCell::new(HashMap::new());
    |                                             ^^^ ------- supplied 1 lifetime argument
@@ -233,7 +265,7 @@ LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, '_, i32>>>>> = Ref
    |                                                        ++++
 
 error[E0106]: missing lifetime specifier
-  --> $DIR/missing-lifetime-specifier.rs:50:44
+  --> $DIR/missing-lifetime-specifier.rs:51:44
    |
 LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, i32>>>>> = RefCell::new(HashMap::new());
    |                                            ^ expected named lifetime parameter
@@ -245,7 +277,7 @@ LL |     static f: RefCell<HashMap<i32, Vec<Vec<&'static Tar<'static, i32>>>>> =
    |                                            ~~~~~~~~
 
 error[E0107]: this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
-  --> $DIR/missing-lifetime-specifier.rs:50:45
+  --> $DIR/missing-lifetime-specifier.rs:51:45
    |
 LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, i32>>>>> = RefCell::new(HashMap::new());
    |                                             ^^^ ------- supplied 1 lifetime argument
@@ -263,19 +295,40 @@ LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'k, i32>>>>> = Ref
    |                                                        ++++
 
 error[E0106]: missing lifetime specifier
-  --> $DIR/missing-lifetime-specifier.rs:50:44
+  --> $DIR/missing-lifetime-specifier.rs:51:44
+   |
+LL | / thread_local! {
+LL | |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, i32>>>>> = RefCell::new(HashMap::new());
+   | |                                            ^ expected named lifetime parameter
+LL | |
+LL | |
+...  |
+LL | |
+LL | | }
+   | |_-
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say which one of `init`'s 3 lifetimes it is borrowed from
+
+error[E0107]: this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
+  --> $DIR/missing-lifetime-specifier.rs:51:45
    |
 LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, i32>>>>> = RefCell::new(HashMap::new());
-   |                                            ^ expected named lifetime parameter
+   |                                             ^^^ ------- supplied 1 lifetime argument
+   |                                             |
+   |                                             expected 2 lifetime arguments
    |
-   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
-help: consider using the `'static` lifetime
+note: trait defined here, with 2 lifetime parameters: `'t`, `'k`
+  --> $DIR/missing-lifetime-specifier.rs:15:7
    |
-LL |     static f: RefCell<HashMap<i32, Vec<Vec<&'static Tar<'static, i32>>>>> = RefCell::new(HashMap::new());
-   |                                            ~~~~~~~~
+LL | trait Tar<'t, 'k, I> {}
+   |       ^^^ --  --
+help: add missing lifetime argument
+   |
+LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'k, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                        ++++
 
 error[E0107]: this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
-  --> $DIR/missing-lifetime-specifier.rs:50:45
+  --> $DIR/missing-lifetime-specifier.rs:51:45
    |
 LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, i32>>>>> = RefCell::new(HashMap::new());
    |                                             ^^^ ------- supplied 1 lifetime argument
@@ -293,7 +346,7 @@ LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'k, i32>>>>> = Ref
    |                                                        ++++
 
 error[E0107]: this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
-  --> $DIR/missing-lifetime-specifier.rs:50:45
+  --> $DIR/missing-lifetime-specifier.rs:51:45
    |
 LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, i32>>>>> = RefCell::new(HashMap::new());
    |                                             ^^^ ------- supplied 1 lifetime argument
@@ -310,7 +363,7 @@ help: add missing lifetime argument
 LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, '_, i32>>>>> = RefCell::new(HashMap::new());
    |                                                        ++++
 
-error: aborting due to 22 previous errors
+error: aborting due to 24 previous errors
 
 Some errors have detailed explanations: E0106, E0107.
 For more information about an error, try `rustc --explain E0106`.
diff --git a/src/test/ui/threads-sendsync/issue-43733.mir.stderr b/src/test/ui/threads-sendsync/issue-43733.mir.stderr
index 0f4b5936dd0..8dc0e75f1af 100644
--- a/src/test/ui/threads-sendsync/issue-43733.mir.stderr
+++ b/src/test/ui/threads-sendsync/issue-43733.mir.stderr
@@ -1,5 +1,5 @@
 error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
-  --> $DIR/issue-43733.rs:17:5
+  --> $DIR/issue-43733.rs:19:5
    |
 LL |     __KEY.get(Default::default)
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
@@ -7,7 +7,7 @@ LL |     __KEY.get(Default::default)
    = note: consult the function's documentation for information on how to avoid undefined behavior
 
 error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
-  --> $DIR/issue-43733.rs:20:42
+  --> $DIR/issue-43733.rs:22:42
    |
 LL | static FOO: std::thread::LocalKey<Foo> = std::thread::LocalKey::new(__getit);
    |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
diff --git a/src/test/ui/threads-sendsync/issue-43733.rs b/src/test/ui/threads-sendsync/issue-43733.rs
index 5434140cd61..9926ed09bb4 100644
--- a/src/test/ui/threads-sendsync/issue-43733.rs
+++ b/src/test/ui/threads-sendsync/issue-43733.rs
@@ -4,6 +4,8 @@
 #![feature(thread_local)]
 #![feature(cfg_target_thread_local, thread_local_internals)]
 
+use std::cell::RefCell;
+
 type Foo = std::cell::RefCell<String>;
 
 #[cfg(target_thread_local)]
@@ -13,7 +15,7 @@ static __KEY: std::thread::__FastLocalKeyInner<Foo> = std::thread::__FastLocalKe
 #[cfg(not(target_thread_local))]
 static __KEY: std::thread::__OsLocalKeyInner<Foo> = std::thread::__OsLocalKeyInner::new();
 
-fn __getit() -> std::option::Option<&'static Foo> {
+fn __getit(_: Option<&mut Option<RefCell<String>>>) -> std::option::Option<&'static Foo> {
     __KEY.get(Default::default) //~ ERROR call to unsafe function is unsafe
 }
 
diff --git a/src/test/ui/threads-sendsync/issue-43733.thir.stderr b/src/test/ui/threads-sendsync/issue-43733.thir.stderr
index 0f4b5936dd0..8dc0e75f1af 100644
--- a/src/test/ui/threads-sendsync/issue-43733.thir.stderr
+++ b/src/test/ui/threads-sendsync/issue-43733.thir.stderr
@@ -1,5 +1,5 @@
 error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
-  --> $DIR/issue-43733.rs:17:5
+  --> $DIR/issue-43733.rs:19:5
    |
 LL |     __KEY.get(Default::default)
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
@@ -7,7 +7,7 @@ LL |     __KEY.get(Default::default)
    = note: consult the function's documentation for information on how to avoid undefined behavior
 
 error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
-  --> $DIR/issue-43733.rs:20:42
+  --> $DIR/issue-43733.rs:22:42
    |
 LL | static FOO: std::thread::LocalKey<Foo> = std::thread::LocalKey::new(__getit);
    |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function