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Merged
bors merged 2 commits into from
Jan 29, 2025
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Merged

Render pattern types nicely in mir dumps #136176

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7877d86
Add mir-opt pattern type tests
oli-obk Jan 28, 2025
fd6713f
Make mir dumps more readable
oli-obk Jan 27, 2025
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15 changes: 15 additions & 0 deletions tests/mir-opt/pattern_types.main.PreCodegen.after.mir
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
// MIR for `main` after PreCodegen

fn main() -> () {
let mut _0: ();
scope 1 {
debug x => const {transmute(0x00000002): (u32) is 1..=};
scope 2 {
debug y => const {transmute(0x00000000): (u32) is 1..=};
}
}

bb0: {
return;
}
}
12 changes: 12 additions & 0 deletions tests/mir-opt/pattern_types.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
#![feature(pattern_types)]
#![feature(pattern_type_macro)]

use std::pat::pattern_type;

// EMIT_MIR pattern_types.main.PreCodegen.after.mir
fn main() {
// CHECK: debug x => const {transmute(0x00000002): (u32) is 1..=}
let x: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(2) };
// CHECK: debug y => const {transmute(0x00000000): (u32) is 1..=}
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@scottmcm scottmcm Jan 28, 2025

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Hmm, definitely interesting. I guess this is falling under the "compilation doesn't have to detect UB" rule?

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@oli-obk oli-obk Jan 28, 2025

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Well... we kinda do because there could be no UB, just const prop crossing a check that prevents UB. So this could happen in dead code. So there is an argument for showing that in pretty printing. I'll see if I can pull out the logic we use in const validation in a way that makes it reusable here

let y: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(0) };
}