Update internal docs & tests to use ! rather than Infallible in relation to Try

compiler/rustc_attr_ir/src/diagnostic.rs

@@ -204,9 +204,9 @@ impl FormatString {
 /// ```rust,ignore (just an example)
 /// FormatArgs {
 ///     this: "FromResidual",
-///     this_resolved: "FromResidual<Option<Infallible>>",
+///     this_resolved: "FromResidual<Option<!>>",
 ///     item_context: "an async function",
-///     generic_args: [("Self", "u32"), ("R", "Option<Infallible>")],
+///     generic_args: [("Self", "u32"), ("R", "Option<!>")],
 /// }
 /// ```
 #[derive(Debug)]
@@ -444,7 +444,7 @@ pub enum LitOrArg {
 ///     crate_local: false,
 ///     direct: true,
 ///     generic_args: [("Self","u32"),
-///         ("R", "core::option::Option<core::convert::Infallible>"),
+///         ("R", "core::option::Option<!>"),
 ///         ("R", "core::option::Option<T>" ),
 ///     ],
 /// }

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -396,7 +396,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                                 // `std::marker::Sized` is not implemented for `T`" as we will point
                                 // at the type param with a label to suggest constraining it.
                                 && !self.tcx.is_diagnostic_item(sym::FromResidual, leaf_trait_predicate.def_id())
-                            // Don't say "the trait `FromResidual<Option<Infallible>>` is
+                            // Don't say "the trait `FromResidual<Option<!>>` is
                             // not implemented for `Result<T, E>`".
                             {
                                 // We do this just so that the JSON output's `help` position is the

src/tools/clippy/clippy_lints/src/methods/mod.rs

@@ -4193,7 +4193,7 @@ declare_clippy_lint! {
     /// ### Why is this bad?
     /// In those cases, the `TryInto` and `TryFrom` trait implementation is a blanket impl that forwards
     /// to `Into` or `From`, which always succeeds.
-    /// The returned `Result<_, Infallible>` requires error handling to get the contained value
+    /// The returned `Result<_, !>` requires error handling to get the contained value
     /// even though the conversion can never fail.
     ///
     /// ### Example

src/tools/clippy/clippy_lints/src/methods/unnecessary_fallible_conversions.rs

@@ -95,7 +95,7 @@ fn check<'tcx>(
         // If `T: TryFrom<U>` and `T: From<U>` both exist, then that means that the `TryFrom`
         // _must_ be from the blanket impl and cannot have been manually implemented
         // (else there would be conflicting impls, even with #![feature(spec)]), so we don't even need to check
-        // what `<T as TryFrom<U>>::Error` is: it's always `Infallible`
+        // what `<T as TryFrom<U>>::Error` is: it's always `!`
         && implements_trait(cx, self_ty, from_into_trait, &[other_ty])
         && let Some(other_ty) = other_ty.as_type()
     {

src/tools/clippy/tests/ui/drop_non_drop.rs

@@ -7,7 +7,7 @@ fn make_result<T>(t: T) -> Result<T, ()> {
 }
 
 // The return type should behave as `T` as the `Err` variant is uninhabited
-fn make_result_uninhabited_err<T>(t: T) -> Result<T, std::convert::Infallible> {
+fn make_result_uninhabited_err<T>(t: T) -> Result<T, !> {
     Ok(t)
 }
 

src/tools/clippy/tests/ui/infallible_try_from.rs

@@ -1,7 +1,5 @@
 #![warn(clippy::infallible_try_from)]
 
-use std::convert::Infallible;
-
 struct MyStruct(i32);
 
 impl TryFrom<i8> for MyStruct {
@@ -14,8 +12,8 @@ impl TryFrom<i8> for MyStruct {
 
 impl TryFrom<i16> for MyStruct {
     //~^ infallible_try_from
-    type Error = Infallible;
-    fn try_from(other: i16) -> Result<Self, Infallible> {
+    type Error = !;
+    fn try_from(other: i16) -> Result<Self, !> {
         Ok(Self(other.into()))
     }
 }

src/tools/clippy/tests/ui/infallible_try_from.stderr

@@ -1,5 +1,5 @@
 error: infallible TryFrom impl; consider implementing From instead
-  --> tests/ui/infallible_try_from.rs:7:1
+  --> tests/ui/infallible_try_from.rs:5:1
    |
 LL | impl TryFrom<i8> for MyStruct {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -11,13 +11,13 @@ LL |     type Error = !;
    = help: to override `-D warnings` add `#[allow(clippy::infallible_try_from)]`
 
 error: infallible TryFrom impl; consider implementing From instead
-  --> tests/ui/infallible_try_from.rs:15:1
+  --> tests/ui/infallible_try_from.rs:13:1
    |
 LL | impl TryFrom<i16> for MyStruct {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
-LL |     type Error = Infallible;
-   |                  ---------- infallible error type
+LL |     type Error = !;
+   |                  - infallible error type
 
 error: aborting due to 2 previous errors
 

src/tools/clippy/tests/ui/let_underscore_must_use.rs

@@ -110,16 +110,24 @@ fn main() {
     let _ = a;
     //~^ let_underscore_must_use
 
+    enum Uninhabited {}
+
     #[allow(clippy::let_underscore_must_use)]
     let _ = a;
 
     // No lint because this type should behave as `()`
-    let _ = Result::<_, std::convert::Infallible>::Ok(());
+    let _ = Result::<_, !>::Ok(());
 
+    // No lint because this type should behave as `()`
+    let _ = Result::<_, Uninhabited>::Ok(());
     #[must_use]
     struct T;
 
     // Lint because this type should behave as `T`
-    let _ = Result::<_, std::convert::Infallible>::Ok(T);
+    let _ = Result::<_, !>::Ok(T);
+    //~^ let_underscore_must_use
+
+    // Lint because this type should behave as `T`
+    let _ = Result::<_, Uninhabited>::Ok(T);
     //~^ let_underscore_must_use
 }

src/tools/clippy/tests/ui/let_underscore_must_use.stderr

@@ -140,17 +140,30 @@ LL |     let _ = a;
    |             ^
 
 error: non-binding `let` on an expression with `#[must_use]` type
-  --> tests/ui/let_underscore_must_use.rs:123:5
+  --> tests/ui/let_underscore_must_use.rs:127:5
    |
-LL |     let _ = Result::<_, std::convert::Infallible>::Ok(T);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     let _ = Result::<_, !>::Ok(T);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider explicitly using expression value
 note: type is `main::T` in a `Result` with an uninhabited error
-  --> tests/ui/let_underscore_must_use.rs:123:13
+  --> tests/ui/let_underscore_must_use.rs:127:13
    |
-LL |     let _ = Result::<_, std::convert::Infallible>::Ok(T);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     let _ = Result::<_, !>::Ok(T);
+   |             ^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 14 previous errors
+error: non-binding `let` on an expression with `#[must_use]` type
+  --> tests/ui/let_underscore_must_use.rs:131:5
+   |
+LL |     let _ = Result::<_, Uninhabited>::Ok(T);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider explicitly using expression value
+note: type is `main::T` in a `Result` with an uninhabited error
+  --> tests/ui/let_underscore_must_use.rs:131:13
+   |
+LL |     let _ = Result::<_, Uninhabited>::Ok(T);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 15 previous errors
 

src/tools/clippy/tests/ui/manual_ok_err.fixed

@@ -76,7 +76,7 @@ fn no_lint() {
         Ok(v) => Some(v),
     };
 
-    let _ = match Ok::<_, std::convert::Infallible>(1) {
+    let _ = match Ok::<_, !>(1) {
         Ok(3) => None,
         Ok(v) => Some(v),
     };

src/tools/clippy/tests/ui/manual_ok_err.rs

@@ -112,7 +112,7 @@ fn no_lint() {
         Ok(v) => Some(v),
     };
 
-    let _ = match Ok::<_, std::convert::Infallible>(1) {
+    let _ = match Ok::<_, !>(1) {
         Ok(3) => None,
         Ok(v) => Some(v),
     };

src/tools/clippy/tests/ui/must_use_candidates.fixed

@@ -102,17 +102,30 @@ pub fn main() -> std::process::ExitCode {
     std::process::ExitCode::SUCCESS
 }
 
+pub enum Uninhabited {}
+
+//~v must_use_candidate
+#[must_use]
+pub fn result_uninhabited_1() -> Result<i32, Uninhabited> {
+    todo!()
+}
+
 //~v must_use_candidate
 #[must_use]
-pub fn result_uninhabited_1() -> Result<i32, std::convert::Infallible> {
+pub fn result_never_1() -> Result<i32, !> {
     todo!()
 }
 
 #[must_use]
 pub struct T;
 
 // Do not lint, `T` is `#[must_use]`, so the `Result<T, uninhabited>` also is.
-pub fn result_uninhabited_2() -> Result<T, std::convert::Infallible> {
+pub fn result_uninhabited_2() -> Result<T, Uninhabited> {
+    todo!()
+}
+
+// Do not lint, `T` is `#[must_use]`, so the `Result<T, uninhabited>` also is.
+pub fn result_never_2() -> Result<T, !> {
     todo!()
 }
 

src/tools/clippy/tests/ui/must_use_candidates.rs

@@ -97,16 +97,28 @@ pub fn main() -> std::process::ExitCode {
     std::process::ExitCode::SUCCESS
 }
 
+pub enum Uninhabited {}
+
+//~v must_use_candidate
+pub fn result_uninhabited_1() -> Result<i32, Uninhabited> {
+    todo!()
+}
+
 //~v must_use_candidate
-pub fn result_uninhabited_1() -> Result<i32, std::convert::Infallible> {
+pub fn result_never_1() -> Result<i32, !> {
     todo!()
 }
 
 #[must_use]
 pub struct T;
 
 // Do not lint, `T` is `#[must_use]`, so the `Result<T, uninhabited>` also is.
-pub fn result_uninhabited_2() -> Result<T, std::convert::Infallible> {
+pub fn result_uninhabited_2() -> Result<T, Uninhabited> {
+    todo!()
+}
+
+// Do not lint, `T` is `#[must_use]`, so the `Result<T, uninhabited>` also is.
+pub fn result_never_2() -> Result<T, !> {
     todo!()
 }
 

src/tools/clippy/tests/ui/must_use_candidates.stderr

@@ -61,16 +61,28 @@ LL | pub fn arcd(_x: Arc<u32>) -> bool {
    |
 
 error: this function could have a `#[must_use]` attribute
-  --> tests/ui/must_use_candidates.rs:101:8
+  --> tests/ui/must_use_candidates.rs:103:8
    |
-LL | pub fn result_uninhabited_1() -> Result<i32, std::convert::Infallible> {
+LL | pub fn result_uninhabited_1() -> Result<i32, Uninhabited> {
    |        ^^^^^^^^^^^^^^^^^^^^
    |
 help: add the attribute
    |
 LL + #[must_use]
-LL | pub fn result_uninhabited_1() -> Result<i32, std::convert::Infallible> {
+LL | pub fn result_uninhabited_1() -> Result<i32, Uninhabited> {
    |
 
-error: aborting due to 6 previous errors
+error: this function could have a `#[must_use]` attribute
+  --> tests/ui/must_use_candidates.rs:108:8
+   |
+LL | pub fn result_never_1() -> Result<i32, !> {
+   |        ^^^^^^^^^^^^^^
+   |
+help: add the attribute
+   |
+LL + #[must_use]
+LL | pub fn result_never_1() -> Result<i32, !> {
+   |
+
+error: aborting due to 7 previous errors
 

src/tools/clippy/tests/ui/single_match_else.fixed

@@ -99,8 +99,16 @@ fn main() {
     //~| NOTE: you might want to preserve the comments from inside the `match`
 
     // lint here
-    use std::convert::Infallible;
-    if let Ok(a) = Result::<i32, &Infallible>::Ok(1) { println!("${:?}", a) } else {
+    if let Ok(a) = Result::<i32, &!>::Ok(1) { println!("${:?}", a) } else {
+        println!("else block");
+        return;
+    }
+    //~^^^^^^^ single_match_else
+
+    enum Uninhabited {}
+
+    // lint here
+    if let Ok(a) = Result::<i32, &Uninhabited>::Ok(1) { println!("${:?}", a) } else {
         println!("else block");
         return;
     }

src/tools/clippy/tests/ui/single_match_else.rs

@@ -112,8 +112,19 @@ fn main() {
     //~| NOTE: you might want to preserve the comments from inside the `match`
 
     // lint here
-    use std::convert::Infallible;
-    match Result::<i32, &Infallible>::Ok(1) {
+    match Result::<i32, &!>::Ok(1) {
+        Ok(a) => println!("${:?}", a),
+        Err(_) => {
+            println!("else block");
+            return;
+        }
+    }
+    //~^^^^^^^ single_match_else
+
+    enum Uninhabited {}
+
+    // lint here
+    match Result::<i32, &Uninhabited>::Ok(1) {
         Ok(a) => println!("${:?}", a),
         Err(_) => {
             println!("else block");