Suggest x build library for a custom toolchain that fails to load core

[mu001999]

Fixes #113222

r? @jyn514

[Noratrieb]

r? Nilstrieb
Have you tested this locally?

[mu001999]

r? Nilstrieb Have you tested this locally?

@Nilstrieb Yes

[Noratrieb]

sounds good, it looks correct to me
@bors r+ rollup

[bors]

📌 Commit b913f55 has been approved by Nilstrieb

It is now in the queue for this repository.

[oli-obk]

I'm getting a bunch of local test failures that are probably due to this PR.

failures:

---- [ui] tests/ui/crate-loading/missing-std.rs stdout ----
diff of stderr:

5	   | ^^^^^^^^^^^^^^^^^^ can't find crate
6	   |
7	   = note: the `x86_64-unknown-uefi` target may not be installed
-	   = help: consider downloading the target with `rustup target add x86_64-unknown-uefi`
+	   = help: consider adding the standard library to the sysroot with `x build library --target x86_64-unknown-uefi`
9	   = help: consider building the standard library from source with `cargo build -Zbuild-std`
10	
11	error: requires `sized` lang_item


The actual stderr differed from the expected stderr.
Actual stderr saved to /home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/test/ui/crate-loading/missing-std/missing-std.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args crate-loading/missing-std.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: CARGO="/usr/bin/cargo" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/stage1/bin/rustc" "/home/ubuntu/rust17/tests/ui/crate-loading/missing-std.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "--sysroot" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/stage1" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/test/ui/crate-loading/missing-std" "-A" "unused" "-Crpath" "-Cdebuginfo=0" "-Lnative=/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/test/ui/crate-loading/missing-std/auxiliary" "--target" "x86_64-unknown-uefi"
stdout: none
--- stderr -------------------------------
error[E0463]: can't find crate for `core`
  --> /home/ubuntu/rust17/tests/ui/crate-loading/missing-std.rs:6:1
   |
LL | extern crate core;
   | ^^^^^^^^^^^^^^^^^^ can't find crate
   |
   = note: the `x86_64-unknown-uefi` target may not be installed
   = help: consider adding the standard library to the sysroot with `x build library --target x86_64-unknown-uefi`
   = help: consider building the standard library from source with `cargo build -Zbuild-std`

error: requires `sized` lang_item

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0463`.
------------------------------------------


---- [ui] tests/ui/issues/issue-49851/compiler-builtins-error.rs stdout ----
diff of stderr:

1	error[E0463]: can't find crate for `core`
2	   |
3	   = note: the `thumbv7em-none-eabihf` target may not be installed
-	   = help: consider downloading the target with `rustup target add thumbv7em-none-eabihf`
+	   = help: consider adding the standard library to the sysroot with `x build library --target thumbv7em-none-eabihf`
5	   = help: consider building the standard library from source with `cargo build -Zbuild-std`
6	
7	error[E0463]: can't find crate for `compiler_builtins`


The actual stderr differed from the expected stderr.
Actual stderr saved to /home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-49851/compiler-builtins-error/compiler-builtins-error.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args issues/issue-49851/compiler-builtins-error.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/stage1/bin/rustc" "/home/ubuntu/rust17/tests/ui/issues/issue-49851/compiler-builtins-error.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "--sysroot" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/stage1" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-49851/compiler-builtins-error" "-A" "unused" "-Crpath" "-Cdebuginfo=0" "-Lnative=/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-49851/compiler-builtins-error/auxiliary" "--target" "thumbv7em-none-eabihf"
stdout: none
--- stderr -------------------------------
error[E0463]: can't find crate for `core`
   |
   = note: the `thumbv7em-none-eabihf` target may not be installed
   = help: consider adding the standard library to the sysroot with `x build library --target thumbv7em-none-eabihf`
   = help: consider building the standard library from source with `cargo build -Zbuild-std`

error[E0463]: can't find crate for `compiler_builtins`

error[E0463]: can't find crate for `cortex_m`
  --> /home/ubuntu/rust17/tests/ui/issues/issue-49851/compiler-builtins-error.rs:10:1
   |
LL | extern crate cortex_m;
   | ^^^^^^^^^^^^^^^^^^^^^^ can't find crate

error: requires `sized` lang_item

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0463`.
------------------------------------------


---- [ui] tests/ui/issues/issue-37131.rs stdout ----
diff of stderr:

1	error[E0463]: can't find crate for `std`
2	   |
3	   = note: the `thumbv6m-none-eabi` target may not be installed
-	   = help: consider downloading the target with `rustup target add thumbv6m-none-eabi`
+	   = help: consider adding the standard library to the sysroot with `x build library --target thumbv6m-none-eabi`
5	   = help: consider building the standard library from source with `cargo build -Zbuild-std`
6	
7	error: requires `sized` lang_item


The actual stderr differed from the expected stderr.
Actual stderr saved to /home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-37131/issue-37131.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args issues/issue-37131.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/stage1/bin/rustc" "/home/ubuntu/rust17/tests/ui/issues/issue-37131.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "--sysroot" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/stage1" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-37131" "-A" "unused" "-Crpath" "-Cdebuginfo=0" "-Lnative=/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/home/ubuntu/rust17/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-37131/auxiliary" "--target=thumbv6m-none-eabi"
stdout: none
--- stderr -------------------------------
error[E0463]: can't find crate for `std`
   |
   = note: the `thumbv6m-none-eabi` target may not be installed
   = help: consider adding the standard library to the sysroot with `x build library --target thumbv6m-none-eabi`
   = help: consider building the standard library from source with `cargo build -Zbuild-std`

error: requires `sized` lang_item

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0463`.
------------------------------------------



failures:
    [ui] tests/ui/crate-loading/missing-std.rs
    [ui] tests/ui/issues/issue-49851/compiler-builtins-error.rs
    [ui] tests/ui/issues/issue-37131.rs

test result: FAILED. 4 passed; 3 failed; 15258 ignored; 0 measured; 0 filtered out; finished in 232.53ms

My config.toml is

changelog-seen = 2
profile = "compiler"

[rust]
debug = true

[jyn514]

hmm. i forgot that CI sets channel = nightly.

@mu001999 i think we should revert this for now until we can come up with a way to test it. maybe we can use nornalize-stderr or something like that? it won't guarantee the new error is being emitted but it at least won't break local tests.