Rollup merge of rust-lang#72052 - lcnr:const_pprint, r=ecstatic-morse

display `ConstKind::Param`

src/librustc_middle/ty/print/pretty.rs

@@ -701,12 +701,14 @@ pub trait PrettyPrinter<'tcx>:
                 if self.tcx().sess.verbose() {
                     p!(write("{:?}", sz));
                 } else if let ty::ConstKind::Unevaluated(..) = sz.val {
-                    // do not try to evaluate unevaluated constants. If we are const evaluating an
+                    // Do not try to evaluate unevaluated constants. If we are const evaluating an
                     // array length anon const, rustc will (with debug assertions) print the
                     // constant's path. Which will end up here again.
                     p!(write("_"));
                 } else if let Some(n) = sz.val.try_to_bits(self.tcx().data_layout.pointer_size) {
                     p!(write("{}", n));
+                } else if let ty::ConstKind::Param(param) = sz.val {
+                    p!(write("{}", param));
                 } else {
                     p!(write("_"));
                 }

src/test/ui/array-slice-vec/match_arr_unknown_len.stderr

@@ -14,7 +14,7 @@ LL |         [1, 2] => true,
    |         ^^^^^^ expected `2usize`, found `N`
    |
    = note: expected array `[u32; 2]`
-              found array `[u32; _]`
+              found array `[u32; N]`
 
 error: aborting due to previous error; 1 warning emitted
 

src/test/ui/const-generics/array-impls/alloc-types-no-impls-length-33.stderr

@@ -29,7 +29,7 @@ LL |     let boxed_array = <Box<[i32; 33]>>::try_from(boxed_slice);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::TryFrom<std::boxed::Box<[i32]>>` is not implemented for `std::boxed::Box<[i32; 33]>`
    |
    = help: the following implementations were found:
-             <std::boxed::Box<[T; _]> as std::convert::TryFrom<std::boxed::Box<[T]>>>
+             <std::boxed::Box<[T; N]> as std::convert::TryFrom<std::boxed::Box<[T]>>>
 
 error[E0277]: the trait bound `std::rc::Rc<[i32; 33]>: std::convert::From<std::rc::Rc<[i32]>>` is not satisfied
   --> $DIR/alloc-types-no-impls-length-33.rs:19:23
@@ -53,7 +53,7 @@ LL |     let boxed_array = <Rc<[i32; 33]>>::try_from(boxed_slice);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::TryFrom<std::rc::Rc<[i32]>>` is not implemented for `std::rc::Rc<[i32; 33]>`
    |
    = help: the following implementations were found:
-             <std::rc::Rc<[T; _]> as std::convert::TryFrom<std::rc::Rc<[T]>>>
+             <std::rc::Rc<[T; N]> as std::convert::TryFrom<std::rc::Rc<[T]>>>
 
 error[E0277]: the trait bound `std::sync::Arc<[i32; 33]>: std::convert::From<std::sync::Arc<[i32]>>` is not satisfied
   --> $DIR/alloc-types-no-impls-length-33.rs:26:23
@@ -77,7 +77,7 @@ LL |     let boxed_array = <Arc<[i32; 33]>>::try_from(boxed_slice);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::TryFrom<std::sync::Arc<[i32]>>` is not implemented for `std::sync::Arc<[i32; 33]>`
    |
    = help: the following implementations were found:
-             <std::sync::Arc<[T; _]> as std::convert::TryFrom<std::sync::Arc<[T]>>>
+             <std::sync::Arc<[T; N]> as std::convert::TryFrom<std::sync::Arc<[T]>>>
 
 error: aborting due to 7 previous errors
 

src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.stderr

@@ -39,9 +39,9 @@ LL |     for _ in &[0_usize; 33] {
    |              ^^^^^^^^^^^^^^ the trait `std::iter::IntoIterator` is not implemented for `&[usize; 33]`
    |
    = help: the following implementations were found:
-             <&'a [T; _] as std::iter::IntoIterator>
+             <&'a [T; N] as std::iter::IntoIterator>
              <&'a [T] as std::iter::IntoIterator>
-             <&'a mut [T; _] as std::iter::IntoIterator>
+             <&'a mut [T; N] as std::iter::IntoIterator>
              <&'a mut [T] as std::iter::IntoIterator>
    = note: required by `std::iter::IntoIterator::into_iter`
 

src/test/ui/const-generics/broken-mir-2.stderr

@@ -11,10 +11,10 @@ error[E0277]: arrays only have std trait implementations for lengths 0..=32
   --> $DIR/broken-mir-2.rs:7:36
    |
 LL | struct S<T: Debug, const N: usize>([T; N]);
-   |                                    ^^^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[T; _]`
+   |                                    ^^^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[T; N]`
    |
-   = note: required because of the requirements on the impl of `std::fmt::Debug` for `[T; _]`
-   = note: required because of the requirements on the impl of `std::fmt::Debug` for `&[T; _]`
+   = note: required because of the requirements on the impl of `std::fmt::Debug` for `[T; N]`
+   = note: required because of the requirements on the impl of `std::fmt::Debug` for `&[T; N]`
    = note: required for the cast to the object type `dyn std::fmt::Debug`
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 

src/test/ui/const-generics/derive-debug-array-wrapper.stderr

@@ -11,10 +11,10 @@ error[E0277]: arrays only have std trait implementations for lengths 0..=32
   --> $DIR/derive-debug-array-wrapper.rs:6:5
    |
 LL |     a: [u32; N],
-   |     ^^^^^^^^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[u32; _]`
+   |     ^^^^^^^^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[u32; N]`
    |
-   = note: required because of the requirements on the impl of `std::fmt::Debug` for `[u32; _]`
-   = note: required because of the requirements on the impl of `std::fmt::Debug` for `&[u32; _]`
+   = note: required because of the requirements on the impl of `std::fmt::Debug` for `[u32; N]`
+   = note: required because of the requirements on the impl of `std::fmt::Debug` for `&[u32; N]`
    = note: required for the cast to the object type `dyn std::fmt::Debug`
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 

src/test/ui/const-generics/issues/issue-62504.stderr

@@ -4,7 +4,7 @@ error[E0308]: mismatched types
 LL |         ArrayHolder([0; Self::SIZE])
    |                     ^^^^^^^^^^^^^^^ expected `X`, found `Self::SIZE`
    |
-   = note: expected array `[u32; _]`
+   = note: expected array `[u32; X]`
               found array `[u32; _]`
 
 error: constant expression depends on a generic parameter