Fix emission of niche-filling discriminant values#55701
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bors merged 1 commit intorust-lang:masterfrom Nov 12, 2018
Merged
Fix emission of niche-filling discriminant values#55701bors merged 1 commit intorust-lang:masterfrom
bors merged 1 commit intorust-lang:masterfrom
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Bug rust-lang#55606 points out a regression introduced by rust-lang#54004; namely that an assertion can erroneously fire when a niche-filling discriminant value is emitted. This fixes the bug by removing the assertion, and furthermore by arranging for the discriminant value to be masked according to the size of the niche. This makes handling the discriminant a bit simpler for debuggers. The test case is from Jonathan Turner. Closes rust-lang#55606
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| // CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "Error",{{.*}}extraData: i64 0{{[,)].*}} | ||
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| #![feature(never_type)] | ||
| #![feature(nll)] |
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This appears to be unnecessary
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@bors r+ |
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Nov 12, 2018
Fix emission of niche-filling discriminant values Bug #55606 points out a regression introduced by #54004; namely that an assertion can erroneously fire when a niche-filling discriminant value is emitted. This fixes the bug by removing the assertion, and furthermore by arranging for the discriminant value to be masked according to the size of the niche. This makes handling the discriminant a bit simpler for debuggers. The test case is from Jonathan Turner. Closes #55606
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☀️ Test successful - status-appveyor, status-travis |
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| .wrapping_add(niche_start); | ||
| assert_eq!(niche as u64 as u128, niche); | ||
| Some(niche as u64) | ||
| let value = value & ((1u128 << niche.value.size(cx).bits()) - 1); |
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Removing the assert is wrong, because you're throwing away bits just below!
After this change, assert_eq!(value as u64 as u128, value); should be between the truncation (let value = value & ...;) and the lossy cast (value as u64).
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Bug #55606 points out a regression introduced by #54004; namely that
an assertion can erroneously fire when a niche-filling discriminant
value is emitted.
This fixes the bug by removing the assertion, and furthermore by
arranging for the discriminant value to be masked according to the
size of the niche. This makes handling the discriminant a bit simpler
for debuggers.
The test case is from Jonathan Turner.
Closes #55606