Do not continue past rustc_resolve when encountering duplicated items

[estebank]

Duplicated items cause lots of confusing knock down errors. This change side-steps some known ICEs, and reduces the verbosity of crates with duplicated items at the cost of not emitting every error that we could.

Noticed just how problematic these can be while looking at #160695, as #[derive]s are particularly prone to the kind of confusion these duplicates cause.

Fix #120873, fix #123690.

r? @petrochenkov

[rustbot]

This PR changes a file inside tests/crashes. If a crash was fixed, please move into the corresponding ui subdir and add 'Fixes #' to the PR description to autoclose the issue upon merge.

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[estebank]

CC @oli-obk as we spent a lot of time some years back removing Fatal.raise() as much as possible, and this is a partial walk-back.

[rust-log-analyzer]

The job test-aarch64-gnu-llvm-21-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

error[E0428]: the name `bar` is defined multiple times
##[error] --> lint_example.rs:8:1
  |
5 | pub fn bar<'a: 'static>() {}
  | ------------------------- previous definition of the value `bar` here
...
8 | pub fn bar<'a: 'b, 'b: 'a>() {}
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `bar` redefined here
  |
  = note: `bar` must be defined only once in the value namespace of this block


error: aborting due to 1 previous error
---
     |
1894 | type Foo<T> = u32; // error: type parameter `T` is never used
     | ------------------ previous definition of the type `Foo` here
1895 | // or:
1896 | type Foo<A, B> = Box<A>;
     | ^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` redefined here
     |
     = note: `Foo` must be defined only once in the type namespace of this block

error: aborting due to 1 previous error

---
    /checkout/obj/build/aarch64-unknown-linux-gnu/test/error-index.md - Rust_Compiler_Error_Index::E0091 (line 1893)

test result: FAILED. 1036 passed; 1 failed; 81 ignored; 0 measured; 0 filtered out; finished in 23.82s

Command `/checkout/obj/build/bootstrap/debug/rustdoc -Wrustdoc::invalid_codeblock_attributes -Dwarnings -Znormalize-docs -Znext-solver=coherence -Z unstable-options --test /checkout/obj/build/aarch64-unknown-linux-gnu/test/error-index.md --test-args ` failed with exit code 101
Created at: src/bootstrap/src/core/builder/mod.rs:1518:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:3320:13

Command has failed. Rerun with -v to see more details.
Bootstrap failed while executing `--stage 2 test --skip tidy --skip intrinsic-test --skip src/tools/rust-analyzer --skip tests --skip library --skip tidyselftest`
Currently active steps:
test::ErrorIndex { compilers: RustcPrivateCompilers { build_compiler: Compiler { stage: 1, host: aarch64-unknown-linux-gnu, forced_compiler: false }, target_compiler: Compiler { stage: 2, host: aarch64-unknown-linux-gnu, forced_compiler: false } } } at src/bootstrap/src/core/build_steps/test.rs:3262
Build completed unsuccessfully in 0:40:04
  local time: Wed Sep 16 21:59:13 UTC 2026