Use Cow instead of &[] for InlineAsm MIR

[Amanieu]

Fixes #72386

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r? @petrochenkov

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[petrochenkov]

CI is failing.

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The job mingw-check of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

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##[section]Starting: Linux mingw-check
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##[section]Finishing: Disable git automatic line ending conversion
##[section]Starting: Checkout rust-lang/rust@refs/pull/72392/merge to s
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---
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Successfully built 537a01811900
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Built container sha256:537a018119009dc218456238dec90b5530050db1e2a1e166550c218003f6159d
---
    Checking rustc_feature v0.0.0 (/checkout/src/librustc_feature)
    Checking fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
    Checking rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
    Checking rustc_hir v0.0.0 (/checkout/src/librustc_hir)
    Checking rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
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error[E0277]: the trait bound `rustc_ast::ast::InlineAsmTemplatePiece: std::marker::Copy` is not satisfied
   --> src/librustc_middle/ty/codec.rs:320:17
    |
138 |    pub fn decode_arena_allocable<D, T: ArenaAllocatable + Decodable>(
    |                                        ---------------- required by this bound in `ty::codec::decode_arena_allocable`
313 | /  macro_rules! impl_arena_allocatable_decoder {
313 | /  macro_rules! impl_arena_allocatable_decoder {
314 | |      ([]$args:tt) => {};
315 | |      ([decode $(, $attrs:ident)*]
316 | |       [[$DecoderName:ident [$($typaram:tt),*]], [$name:ident: $ty:ty], $tcx:lifetime]) => {
320 | |                  decode_arena_allocable(self)
320 | |                  decode_arena_allocable(self)
    | |                  ^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `rustc_ast::ast::InlineAsmTemplatePiece`
333 | |      };
334 | |  }
334 | |  }
    | |__- in this expansion of `impl_arena_allocatable_decoder!` (#4)
337 | /  macro_rules! impl_arena_allocatable_decoders {
337 | /  macro_rules! impl_arena_allocatable_decoders {
338 | |      ($args:tt, [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
339 | |          $(
340 | |              impl_arena_allocatable_decoder!($a [$args, [$name: $ty], $tcx]);
341 | |          )*
342 | |      }
343 | |  }
343 | |  }
    | |__- in this expansion of `impl_arena_allocatable_decoders!` (#3)
346 | /  macro_rules! implement_ty_decoder {
346 | /  macro_rules! implement_ty_decoder {
347 | |      ($DecoderName:ident <$($typaram:tt),*>) => {
348 | |          mod __ty_decoder_impl {
349 | |              use std::borrow::Cow;
...   |
399 | |              rustc_hir::arena_types!(impl_arena_allocatable_decoders, [$DecoderName [$($typaram),*]], 'tcx);
...   |
494 | |      }
495 | |  }
495 | |  }
    | |__- in this expansion of `implement_ty_decoder!` (#1)
    | 
   ::: src/librustc_middle/ty/query/on_disk_cache.rs:558:1
    |
558 |    implement_ty_decoder!(CacheDecoder<'a, 'tcx>);
    | 
   ::: /checkout/src/librustc_hir/arena.rs:11:1
    |
    |
11  |  / macro_rules! arena_types {
12  |  |     ($macro:path, $args:tt, $tcx:lifetime) => (
13  |  |         $macro!($args, [
14  | ||             // HIR types
14  | ||             // HIR types
15  | ||             [few] hir_krate: rustc_hir::Crate<$tcx>,
16  | ||             [] arm: rustc_hir::Arm<$tcx>,
...   ||
49  | ||             [] where_predicate: rustc_hir::WherePredicate<$tcx>,
50  | ||         ], $tcx);
    | ||_________________- in this macro invocation (#3)
52  |  | }
52  |  | }
    |  |_- in this expansion of `rustc_hir::arena_types!` (#2)
    |
    = note: required because of the requirements on the impl of `arena::ArenaAllocatable` for `rustc_ast::ast::InlineAsmTemplatePiece`

error[E0277]: the trait bound `rustc_ast::ast::InlineAsmTemplatePiece: std::marker::Copy` is not satisfied
   --> src/librustc_middle/ty/codec.rs:327:17
    |
148 |    pub fn decode_arena_allocable_slice<D, T: ArenaAllocatable + Decodable>(
    |                                              ---------------- required by this bound in `ty::codec::decode_arena_allocable_slice`
313 | /  macro_rules! impl_arena_allocatable_decoder {
313 | /  macro_rules! impl_arena_allocatable_decoder {
314 | |      ([]$args:tt) => {};
315 | |      ([decode $(, $attrs:ident)*]
316 | |       [[$DecoderName:ident [$($typaram:tt),*]], [$name:ident: $ty:ty], $tcx:lifetime]) => {
327 | |                  decode_arena_allocable_slice(self)
327 | |                  decode_arena_allocable_slice(self)
    | |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `rustc_ast::ast::InlineAsmTemplatePiece`
333 | |      };
334 | |  }
334 | |  }
    | |__- in this expansion of `impl_arena_allocatable_decoder!` (#4)
337 | /  macro_rules! impl_arena_allocatable_decoders {
337 | /  macro_rules! impl_arena_allocatable_decoders {
338 | |      ($args:tt, [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
339 | |          $(
340 | |              impl_arena_allocatable_decoder!($a [$args, [$name: $ty], $tcx]);
341 | |          )*
342 | |      }
343 | |  }
343 | |  }
    | |__- in this expansion of `impl_arena_allocatable_decoders!` (#3)
346 | /  macro_rules! implement_ty_decoder {
346 | /  macro_rules! implement_ty_decoder {
347 | |      ($DecoderName:ident <$($typaram:tt),*>) => {
348 | |          mod __ty_decoder_impl {
349 | |              use std::borrow::Cow;
...   |
399 | |              rustc_hir::arena_types!(impl_arena_allocatable_decoders, [$DecoderName [$($typaram),*]], 'tcx);
...   |
494 | |      }
495 | |  }
495 | |  }
    | |__- in this expansion of `implement_ty_decoder!` (#1)
    | 
   ::: src/librustc_middle/ty/query/on_disk_cache.rs:558:1
    |
558 |    implement_ty_decoder!(CacheDecoder<'a, 'tcx>);
    | 
   ::: /checkout/src/librustc_hir/arena.rs:11:1
    |
    |
11  |  / macro_rules! arena_types {
12  |  |     ($macro:path, $args:tt, $tcx:lifetime) => (
13  |  |         $macro!($args, [
14  | ||             // HIR types
14  | ||             // HIR types
15  | ||             [few] hir_krate: rustc_hir::Crate<$tcx>,
16  | ||             [] arm: rustc_hir::Arm<$tcx>,
...   ||
49  | ||             [] where_predicate: rustc_hir::WherePredicate<$tcx>,
50  | ||         ], $tcx);
    | ||_________________- in this macro invocation (#3)
52  |  | }
52  |  | }
    |  |_- in this expansion of `rustc_hir::arena_types!` (#2)
    |
    = note: required because of the requirements on the impl of `arena::ArenaAllocatable` for `rustc_ast::ast::InlineAsmTemplatePiece`
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.
error: could not compile `rustc_middle`.
error: could not compile `rustc_middle`.

To learn more, run the command again with --verbose.
command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "check" "--target" "x86_64-unknown-linux-gnu" "-Zbinary-dep-depinfo" "-j" "2" "--release" "--color" "always" "--features" " llvm" "--manifest-path" "/checkout/src/rustc/Cargo.toml" "--message-format" "json-render-diagnostics"
failed to run: /checkout/obj/build/bootstrap/debug/bootstrap check
Build completed unsuccessfully in 0:04:26
== clock drift check ==
  local time: Wed May 20 20:50:47 UTC 2020
  local time: Wed May 20 20:50:47 UTC 2020
  network time: Wed, 20 May 2020 20:50:47 GMT
== end clock drift check ==

##[error]Bash exited with code '1'.
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[Amanieu]

I reverted back to my original approach which uses Cow.

[Amanieu]

Closing in favor of #72400