Emit a pre-expansion feature gate warning for box'ed struct field patterns#154475
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box'ed struct field patterns
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tests/ui/auto-traits/pre-cfg.rs
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Replaced by tests/ui/feature-gates/soft-feature-gate-auto_traits.rs.
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Replaced by tests/ui/feature-gates/soft-feature-gate-try_blocks.rs.
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Rollup of 11 pull requests Successful merges: - #152880 (Tweak incorrect assoc item note) - #153526 (Fix LegacyKeyValueFormat report from docker build: i686) - #153613 (interpreter error reporting: remove arguments that are always the same) - #154029 (Replace `truncate(0)` with `clear()`) - #154125 (Inline and remove `DepGraphData::try_mark_parent_green`.) - #154185 (Prevent no_threads RwLock's write() impl from setting mode to -1 when it is locked for reading) - #154394 (Normalize rustc path prefix when testing `-Z track-diagnostics`) - #154450 (Use the normal arg-parsing machinery for `-Zassert-incr-state`) - #154475 (Emit a pre-expansion feature gate warning for `box`'ed struct field patterns) - #154500 (EnumSizeOpt: use Allocation::write_scalar instead of manual endianess logic) - #154502 (interpret: ensure that untupled arguments are actually tuples)
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Rollup merge of #154475 - fmease:soft-gate-box-struct-field-pat, r=Kivooeo Emit a pre-expansion feature gate warning for `box`'ed struct field patterns While the following code triggers a feature gate *warning*: ```rs fn f() { #[cfg(false)] let box x; //~ WARN box pattern syntax is experimental } ``` the code below does not (on stable & main): ```rs fn f() { #[cfg(false)] let Struct { box x }; } ``` This is an oversight as both are part of the unstable feature `box_patterns` (that isn't properly gated pre expansion for historical reasons). Of course, both forms lead to a feature gate error *post expansion*. This is a bug fix and doesn't need any input from T-compiler or T-lang. For context, emitting warnings in these cases is legitimized by [MCP 535](https://github.com/rust-lang/compiler-team/issues/535)[^1]. Part of #154045. [^1]: In case you're wondering why the MCP talks about a *lint* even though the feature gate warnings as seen today don't reference any lint by name, read #154045 (comment).
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While the following code triggers a feature gate warning:
the code below does not (on stable & main):
This is an oversight as both are part of the unstable feature
box_patterns(that isn't properly gated pre expansion for historical reasons). Of course, both forms lead to a feature gate error post expansion.This is a bug fix and doesn't need any input from T-compiler or T-lang. For context, emitting warnings in these cases is legitimized by MCP 5351.
Part of #154045.
Footnotes
In case you're wondering why the MCP talks about a lint even though the feature gate warnings as seen today don't reference any lint by name, read https://github.com/rust-lang/rust/issues/154045#issuecomment-4144034419. ↩