Fix mixed use of "a" / "an" article in E0277

library/core/src/ops/function.rs

@@ -67,7 +67,7 @@ use crate::marker::Tuple;
         // SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
         label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
     ),
-    message = "expected a `{This:resolved}` closure, found `{Self}`",
+    message = "expected an `{This:resolved}` closure, found `{Self}`",
     label = "expected an `{This:resolved}` closure, found `{Self}`"
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
@@ -154,7 +154,7 @@ pub const trait Fn<Args: Tuple>: [const] FnMut<Args> {
         // SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
         label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
     ),
-    message = "expected a `{This:resolved}` closure, found `{Self}`",
+    message = "expected an `{This:resolved}` closure, found `{Self}`",
     label = "expected an `{This:resolved}` closure, found `{Self}`"
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
@@ -233,7 +233,7 @@ pub const trait FnMut<Args: Tuple>: FnOnce<Args> {
         // SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
         label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
     ),
-    message = "expected a `{This:resolved}` closure, found `{Self}`",
+    message = "expected an `{This:resolved}` closure, found `{Self}`",
     label = "expected an `{This:resolved}` closure, found `{Self}`"
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`

tests/ui/abi/bad-custom.rs

@@ -100,7 +100,7 @@ async unsafe extern "custom" fn no_async_fn() {
 }
 
 fn no_promotion_to_fn_trait(f: unsafe extern "custom" fn()) -> impl Fn()  {
-    //~^ ERROR expected a `Fn()` closure, found `unsafe extern "custom" fn()`
+    //~^ ERROR expected an `Fn()` closure, found `unsafe extern "custom" fn()`
     f
 }
 

tests/ui/abi/bad-custom.stderr

@@ -184,7 +184,7 @@ LL + #[unsafe(naked)]
 LL | async unsafe extern "custom" fn no_async_fn() {
    |
 
-error[E0277]: expected a `Fn()` closure, found `unsafe extern "custom" fn()`
+error[E0277]: expected an `Fn()` closure, found `unsafe extern "custom" fn()`
   --> $DIR/bad-custom.rs:102:64
    |
 LL | fn no_promotion_to_fn_trait(f: unsafe extern "custom" fn()) -> impl Fn()  {

tests/ui/associated-types/normalization-ice-issue-149746.rs

@@ -4,14 +4,14 @@ trait Owner { type Ty<T: FnMut()>; }
 impl Owner for () { type Ty<T: FnMut()> = T; }
 pub struct Warns<T> {
     _significant_drop: <() as Owner>::Ty<T>,
-    //~^ ERROR expected a `FnMut()` closure, found `T`
+    //~^ ERROR expected an `FnMut()` closure, found `T`
     field: String,
 }
 pub fn test<T>(w: Warns<T>) {
-    //~^ ERROR expected a `FnMut()` closure, found `T`
+    //~^ ERROR expected an `FnMut()` closure, found `T`
     _ = || w.field
-    //~^ ERROR expected a `FnMut()` closure, found `T`
-    //~| ERROR expected a `FnMut()` closure, found `T`
+    //~^ ERROR expected an `FnMut()` closure, found `T`
+    //~| ERROR expected an `FnMut()` closure, found `T`
     //~| WARN: changes to closure capture in Rust 2021 will affect drop order
 }
 fn main() {}

tests/ui/associated-types/normalization-ice-issue-149746.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `FnMut()` closure, found `T`
+error[E0277]: expected an `FnMut()` closure, found `T`
   --> $DIR/normalization-ice-issue-149746.rs:6:24
    |
 LL |     _significant_drop: <() as Owner>::Ty<T>,
@@ -35,7 +35,7 @@ help: add a dummy let to cause `w` to be fully captured
 LL |     _ = || { let _ = &w; w.field }
    |            +++++++++++++         +
 
-error[E0277]: expected a `FnMut()` closure, found `T`
+error[E0277]: expected an `FnMut()` closure, found `T`
   --> $DIR/normalization-ice-issue-149746.rs:12:9
    |
 LL |     _ = || w.field
@@ -48,7 +48,7 @@ note: required by a bound in `Owner::Ty`
 LL | trait Owner { type Ty<T: FnMut()>; }
    |                          ^^^^^^^ required by this bound in `Owner::Ty`
 
-error[E0277]: expected a `FnMut()` closure, found `T`
+error[E0277]: expected an `FnMut()` closure, found `T`
   --> $DIR/normalization-ice-issue-149746.rs:10:16
    |
 LL | pub fn test<T>(w: Warns<T>) {
@@ -61,7 +61,7 @@ note: required by a bound in `Owner::Ty`
 LL | trait Owner { type Ty<T: FnMut()>; }
    |                          ^^^^^^^ required by this bound in `Owner::Ty`
 
-error[E0277]: expected a `FnMut()` closure, found `T`
+error[E0277]: expected an `FnMut()` closure, found `T`
   --> $DIR/normalization-ice-issue-149746.rs:12:9
    |
 LL |     _ = || w.field

tests/ui/async-await/async-fn/impl-header.rs

@@ -6,7 +6,7 @@ impl async Fn<()> for F {}
 //~^ ERROR `async` trait implementations are unsupported
 //~| ERROR the precise format of `Fn`-family traits' type parameters is subject to change
 //~| ERROR manual implementations of `Fn` are experimental
-//~| ERROR expected a `FnMut()` closure, found `F`
+//~| ERROR expected an `FnMut()` closure, found `F`
 //~| ERROR not all trait items implemented, missing: `call`
 
 fn main() {}

tests/ui/async-await/async-fn/impl-header.stderr

@@ -30,7 +30,7 @@ LL | impl async Fn<()> for F {}
    |
    = help: implement the missing item: `fn call(&self, _: ()) -> <Self as FnOnce<()>>::Output { todo!() }`
 
-error[E0277]: expected a `FnMut()` closure, found `F`
+error[E0277]: expected an `FnMut()` closure, found `F`
   --> $DIR/impl-header.rs:5:23
    |
 LL | impl async Fn<()> for F {}

tests/ui/cast/raw-ptr-to-dyn-fn-raw-ptr.rs

@@ -4,6 +4,6 @@ fn main() {
     let ptr: *mut () = core::ptr::null_mut();
     let _: &mut dyn Fn() = unsafe {
         &mut *(ptr as *mut dyn Fn())
-        //~^ ERROR expected a `Fn()` closure, found `()`
+        //~^ ERROR expected an `Fn()` closure, found `()`
     };
 }

tests/ui/cast/raw-ptr-to-dyn-fn-raw-ptr.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `Fn()` closure, found `()`
+error[E0277]: expected an `Fn()` closure, found `()`
   --> $DIR/raw-ptr-to-dyn-fn-raw-ptr.rs:6:16
    |
 LL |         &mut *(ptr as *mut dyn Fn())

tests/ui/closures/closure-expected.rs

@@ -1,5 +1,5 @@
 fn main() {
     let x = Some(1);
     let y = x.or_else(4);
-    //~^ ERROR expected a `FnOnce()` closure, found `{integer}`
+    //~^ ERROR expected an `FnOnce()` closure, found `{integer}`
 }

tests/ui/closures/closure-expected.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `FnOnce()` closure, found `{integer}`
+error[E0277]: expected an `FnOnce()` closure, found `{integer}`
   --> $DIR/closure-expected.rs:3:23
    |
 LL |     let y = x.or_else(4);

tests/ui/closures/coerce-unsafe-to-closure.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `FnOnce(&str)` closure, found `unsafe fn(_) -> _ {std::intrinsics::transmute::<_, _>}`
+error[E0277]: expected an `FnOnce(&str)` closure, found `unsafe fn(_) -> _ {std::intrinsics::transmute::<_, _>}`
   --> $DIR/coerce-unsafe-to-closure.rs:2:44
    |
 LL |     let x: Option<&[u8]> = Some("foo").map(std::mem::transmute);

tests/ui/contracts/empty-ensures.rs

@@ -6,7 +6,7 @@ extern crate core;
 use core::contracts::ensures;
 
 #[ensures()]
-//~^ ERROR expected a `Fn(&_)` closure, found `()` [E0277]
+//~^ ERROR expected an `Fn(&_)` closure, found `()` [E0277]
 fn foo(x: u32) -> u32 {
     x * 2
 }

tests/ui/contracts/empty-ensures.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `Fn(&_)` closure, found `()`
+error[E0277]: expected an `Fn(&_)` closure, found `()`
   --> $DIR/empty-ensures.rs:8:1
    |
 LL | #[ensures()]

tests/ui/expr/malformed_closure/block_instead_of_closure_in_arg.rs

@@ -1,6 +1,6 @@
 fn main() {
     let number = 2;
-    Some(true).filter({ //~ ERROR expected a `FnOnce(&bool)` closure, found `bool`
+    Some(true).filter({ //~ ERROR expected an `FnOnce(&bool)` closure, found `bool`
         if number % 2 == 0 {
             number == 0
         } else {

tests/ui/expr/malformed_closure/block_instead_of_closure_in_arg.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `FnOnce(&bool)` closure, found `bool`
+error[E0277]: expected an `FnOnce(&bool)` closure, found `bool`
   --> $DIR/block_instead_of_closure_in_arg.rs:3:23
    |
 LL |        Some(true).filter({

tests/ui/expr/malformed_closure/ruby_style_closure_successful_parse.rs

@@ -1,6 +1,6 @@
 const x: usize =42;
 fn main() {
-    let p = Some(45).and_then({|x| //~ ERROR expected a `FnOnce({integer})` closure, found `Option<usize>`
+    let p = Some(45).and_then({|x| //~ ERROR expected an `FnOnce({integer})` closure, found `Option<usize>`
         1 + 1;
         Some(x * 2)
     });

tests/ui/expr/malformed_closure/ruby_style_closure_successful_parse.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `FnOnce({integer})` closure, found `Option<usize>`
+error[E0277]: expected an `FnOnce({integer})` closure, found `Option<usize>`
   --> $DIR/ruby_style_closure_successful_parse.rs:3:31
    |
 LL |       let p = Some(45).and_then({|x|

tests/ui/extern/extern-wrong-value-type.rs

@@ -7,5 +7,5 @@ fn main() {
     // extern functions are extern "C" fn
     let _x: extern "C" fn() = f; // OK
     is_fn(f);
-    //~^ ERROR expected a `Fn()` closure, found `extern "C" fn() {f}`
+    //~^ ERROR expected an `Fn()` closure, found `extern "C" fn() {f}`
 }

tests/ui/extern/extern-wrong-value-type.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `Fn()` closure, found `extern "C" fn() {f}`
+error[E0277]: expected an `Fn()` closure, found `extern "C" fn() {f}`
   --> $DIR/extern-wrong-value-type.rs:9:11
    |
 LL |     is_fn(f);

tests/ui/feature-gates/feature-gate-unboxed-closures-manual-impls.rs

@@ -9,7 +9,7 @@ struct Foo;
 impl Fn<()> for Foo {
     //~^ ERROR the precise format of `Fn`-family traits' type parameters is subject to change
     //~| ERROR manual implementations of `Fn` are experimental
-    //~| ERROR expected a `FnMut()` closure, found `Foo`
+    //~| ERROR expected an `FnMut()` closure, found `Foo`
     extern "rust-call" fn call(self, args: ()) -> () {}
     //~^ ERROR "rust-call" ABI is experimental and subject to change
     //~| ERROR `call` has an incompatible type for trait
@@ -26,7 +26,7 @@ struct Bar;
 impl FnMut<()> for Bar {
     //~^ ERROR the precise format of `Fn`-family traits' type parameters is subject to change
     //~| ERROR manual implementations of `FnMut` are experimental
-    //~| ERROR expected a `FnOnce()` closure, found `Bar`
+    //~| ERROR expected an `FnOnce()` closure, found `Bar`
     extern "rust-call" fn call_mut(&self, args: ()) -> () {}
     //~^ ERROR "rust-call" ABI is experimental and subject to change
     //~| ERROR incompatible type for trait

tests/ui/feature-gates/feature-gate-unboxed-closures-manual-impls.stderr

@@ -87,7 +87,7 @@ LL | impl FnMut<()> for Bar {
    |
    = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
 
-error[E0277]: expected a `FnMut()` closure, found `Foo`
+error[E0277]: expected an `FnMut()` closure, found `Foo`
   --> $DIR/feature-gate-unboxed-closures-manual-impls.rs:9:17
    |
 LL | impl Fn<()> for Foo {
@@ -161,7 +161,7 @@ help: change the self-receiver type to match the trait
 LL |     extern "rust-call" fn call_mut(&mut self, args: ()) -> () {}
    |                                     +++
 
-error[E0277]: expected a `FnOnce()` closure, found `Bar`
+error[E0277]: expected an `FnOnce()` closure, found `Bar`
   --> $DIR/feature-gate-unboxed-closures-manual-impls.rs:26:20
    |
 LL | impl FnMut<()> for Bar {

tests/ui/fn/fn-trait-formatting.rs

@@ -17,5 +17,5 @@ fn main() {
     //~| NOTE found struct `Box<dyn FnMut() -> isize>`
 
     needs_fn(1);
-    //~^ ERROR expected a `Fn(isize)` closure, found `{integer}`
+    //~^ ERROR expected an `Fn(isize)` closure, found `{integer}`
 }

tests/ui/fn/fn-trait-formatting.stderr

@@ -39,7 +39,7 @@ LL |     let _: () = Box::new(|| -> isize { unimplemented!() }) as Box<dyn FnMut
    = note: expected unit type `()`
                  found struct `Box<dyn FnMut() -> isize>`
 
-error[E0277]: expected a `Fn(isize)` closure, found `{integer}`
+error[E0277]: expected an `Fn(isize)` closure, found `{integer}`
   --> $DIR/fn-trait-formatting.rs:19:14
    |
 LL |     needs_fn(1);

tests/ui/fn/issue-39259.rs

@@ -5,7 +5,7 @@ struct S;
 
 impl Fn(u32) -> u32 for S {
     //~^ ERROR associated item constraints are not allowed here [E0229]
-    //~| ERROR expected a `FnMut(u32)` closure, found `S`
+    //~| ERROR expected an `FnMut(u32)` closure, found `S`
     fn call(&self) -> u32 {
         //~^ ERROR method `call` has 1 parameter but the declaration in trait `call` has 2
         5

tests/ui/fn/issue-39259.stderr

@@ -22,7 +22,7 @@ help: add the missing parameter from the trait
 LL |     fn call(&self, args: Args) -> u32 {
    |                  ++++++++++++
 
-error[E0277]: expected a `FnMut(u32)` closure, found `S`
+error[E0277]: expected an `FnMut(u32)` closure, found `S`
   --> $DIR/issue-39259.rs:6:25
    |
 LL | impl Fn(u32) -> u32 for S {

tests/ui/generic-associated-types/issue-68642-broken-llvm-ir.rs

@@ -10,7 +10,7 @@ trait Fun {
 
 impl<T> Fun for T {
     type F<'a> = Self;
-    //~^ ERROR expected a `Fn()` closure, found `T`
+    //~^ ERROR expected an `Fn()` closure, found `T`
 }
 
 fn main() {

tests/ui/generic-associated-types/issue-68642-broken-llvm-ir.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `Fn()` closure, found `T`
+error[E0277]: expected an `Fn()` closure, found `T`
   --> $DIR/issue-68642-broken-llvm-ir.rs:12:18
    |
 LL |     type F<'a> = Self;

tests/ui/generic-associated-types/issue-68643-broken-mir.rs

@@ -10,7 +10,7 @@ trait Fun {
 
 impl<T> Fun for T {
     type F<'a> = Self;
-    //~^ ERROR expected a `Fn()` closure, found `T`
+    //~^ ERROR expected an `Fn()` closure, found `T`
 }
 
 pub fn main() {

tests/ui/generic-associated-types/issue-68643-broken-mir.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `Fn()` closure, found `T`
+error[E0277]: expected an `Fn()` closure, found `T`
   --> $DIR/issue-68643-broken-mir.rs:12:18
    |
 LL |     type F<'a> = Self;

tests/ui/generic-associated-types/issue-68644-codegen-selection.rs

@@ -10,7 +10,7 @@ trait Fun {
 
 impl<T> Fun for T {
     type F<'a> = Self;
-    //~^ ERROR expected a `Fn()` closure, found `T`
+    //~^ ERROR expected an `Fn()` closure, found `T`
 }
 
 fn main() {

tests/ui/generic-associated-types/issue-68644-codegen-selection.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `Fn()` closure, found `T`
+error[E0277]: expected an `Fn()` closure, found `T`
   --> $DIR/issue-68644-codegen-selection.rs:12:18
    |
 LL |     type F<'a> = Self;

tests/ui/generic-associated-types/issue-68645-codegen-fulfillment.rs

@@ -10,7 +10,7 @@ trait Fun {
 
 impl<T> Fun for T {
     type F<'a> = Self;
-    //~^ ERROR expected a `Fn()` closure, found `T`
+    //~^ ERROR expected an `Fn()` closure, found `T`
 }
 
 fn main() {

tests/ui/generic-associated-types/issue-68645-codegen-fulfillment.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `Fn()` closure, found `T`
+error[E0277]: expected an `Fn()` closure, found `T`
   --> $DIR/issue-68645-codegen-fulfillment.rs:12:18
    |
 LL |     type F<'a> = Self;

tests/ui/higher-ranked/trait-bounds/normalize-under-binder/issue-62529-3.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `Fn(<_ as ATC<'a>>::Type)` closure, found `F`
+error[E0277]: expected an `Fn(<_ as ATC<'a>>::Type)` closure, found `F`
   --> $DIR/issue-62529-3.rs:25:14
    |
 LL |         call(f, ());

tests/ui/implied-bounds/issue-100690.rs

@@ -32,7 +32,7 @@ impl<'a, T: 'a> Handle<'a, T, UIView<'a, T>, Result<(), io::Error>> for TUIHandl
         F: FnOnce(&mut UIView<'a, T>) -> Result<(), io::Error> + Send + 'static,
     {
         real_dispatch(f)
-        //~^ ERROR expected a `FnOnce(&mut UIView<'_, T>)` closure, found `F`
+        //~^ ERROR expected an `FnOnce(&mut UIView<'_, T>)` closure, found `F`
     }
 }
 

tests/ui/implied-bounds/issue-100690.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `FnOnce(&mut UIView<'_, T>)` closure, found `F`
+error[E0277]: expected an `FnOnce(&mut UIView<'_, T>)` closure, found `F`
   --> $DIR/issue-100690.rs:34:23
    |
 LL |         real_dispatch(f)

tests/ui/intrinsics/const-eval-select-bad.rs

@@ -7,8 +7,8 @@ const fn not_fn_items() {
     const_eval_select((), || {}, || {});
     //~^ ERROR const FnOnce()` is not satisfied
     const_eval_select((), 42, 0xDEADBEEF);
-    //~^ ERROR expected a `FnOnce()` closure
-    //~| ERROR expected a `FnOnce()` closure
+    //~^ ERROR expected an `FnOnce()` closure
+    //~| ERROR expected an `FnOnce()` closure
 }
 
 const fn foo(n: i32) -> i32 {

tests/ui/intrinsics/const-eval-select-bad.stderr

@@ -9,7 +9,7 @@ LL |     const_eval_select((), || {}, || {});
 note: required by a bound in `const_eval_select`
   --> $SRC_DIR/core/src/intrinsics/mod.rs:LL:COL
 
-error[E0277]: expected a `FnOnce()` closure, found `{integer}`
+error[E0277]: expected an `FnOnce()` closure, found `{integer}`
   --> $DIR/const-eval-select-bad.rs:9:27
    |
 LL |     const_eval_select((), 42, 0xDEADBEEF);
@@ -22,7 +22,7 @@ LL |     const_eval_select((), 42, 0xDEADBEEF);
 note: required by a bound in `const_eval_select`
   --> $SRC_DIR/core/src/intrinsics/mod.rs:LL:COL
 
-error[E0277]: expected a `FnOnce()` closure, found `{integer}`
+error[E0277]: expected an `FnOnce()` closure, found `{integer}`
   --> $DIR/const-eval-select-bad.rs:9:31
    |
 LL |     const_eval_select((), 42, 0xDEADBEEF);

tests/ui/iterators/fold-iterator-error-23966.stderr

@@ -1,4 +1,4 @@
-error[E0277]: expected a `FnMut(_, char)` closure, found `()`
+error[E0277]: expected an `FnMut(_, char)` closure, found `()`
   --> $DIR/fold-iterator-error-23966.rs:3:32
    |
 LL |     "".chars().fold(|_, _| (), ());