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Diffstat (limited to '')
| -rw-r--r-- | tests/ui/proc-macro/issue-75930-derive-cfg.rs | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/tests/ui/proc-macro/issue-75930-derive-cfg.rs b/tests/ui/proc-macro/issue-75930-derive-cfg.rs index ef56e8e02..e0213527c 100644 --- a/tests/ui/proc-macro/issue-75930-derive-cfg.rs +++ b/tests/ui/proc-macro/issue-75930-derive-cfg.rs @@ -16,6 +16,36 @@ extern crate std; #[macro_use] extern crate test_macros; +// Note: the expected output contains this sequence: +// ``` +// Punct { +// ch: '<', +// spacing: Joint, +// span: $DIR/issue-75930-derive-cfg.rs:25:11: 25:12 (#0), +// }, +// Ident { +// ident: "B", +// span: $DIR/issue-75930-derive-cfg.rs:25:29: 25:30 (#0), +// }, +// ``` +// It's surprising to see a `Joint` token tree followed by an `Ident` token +// tree, because `Joint` is supposed to only be used if the following token is +// `Punct`. +// +// It is because of this code from below: +// ``` +// struct Foo<#[cfg(FALSE)] A, B> +// ``` +// When the token stream is formed during parsing, `<` is followed immediately +// by `#`, which is punctuation, so it is marked `Joint`. But before being +// passed to the proc macro it is rewritten to this: +// ``` +// struct Foo<B> +// ``` +// But the `Joint` marker on the `<` is not updated. Perhaps it should be +// corrected before being passed to the proc macro? But a prior attempt to do +// that kind of correction caused the problem seen in #76399, so maybe not. + #[print_helper(a)] //~ WARN derive helper attribute is used before it is introduced //~| WARN this was previously accepted #[cfg_attr(not(FALSE), allow(dead_code))] |