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Add test self-in-enum-definition #62916

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Jul 24, 2019
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Add test self-in-enum-definition #62916

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2e193f7
Add test self-in-enum-definition
Centril Jul 23, 2019
7fdfe8b
Refer to #50072 re. hack.
Centril Jul 24, 2019
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8 changes: 8 additions & 0 deletions src/test/ui/type-alias-enum-variants/self-in-enum-definition.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
#[repr(u8)]
enum Alpha {
V1 = 41,
V2 = Self::V1 as u8 + 1, // OK -- but why?
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Really... why?

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oh you're gonna lovehate this

  1. latest nightly won't compile old versions of winapi #49765
  2. Allow variant discriminant initializers to refer to other initializer… #50072
  3. [DO NOT MERGE] see what breaks when we remove this recursive-enum-discriminants hack #61723

It's a peephole hack for excactly Enum::Variant as int

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I thought it felt familiar... 😭.

At some point we should do what @RalfJung suggested in #61723 (comment) since Ralf is right that this is so incredibly niche and imo clearly a bug...

Oh well... not much to do about it here!

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Adjusted the comment to refer to #50072... Should be good to merge now. :)

V3 = Self::V1 {} as u8 + 2, //~ ERROR cycle detected when const-evaluating
}

fn main() {}
28 changes: 28 additions & 0 deletions src/test/ui/type-alias-enum-variants/self-in-enum-definition.stderr
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Original file line number Diff line number Diff line change
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error[E0391]: cycle detected when const-evaluating + checking `Alpha::V3::{{constant}}#0`
--> $DIR/self-in-enum-definition.rs:5:10
|
LL | V3 = Self::V1 {} as u8 + 2,
| ^^^^^^^^
|
note: ...which requires const-evaluating `Alpha::V3::{{constant}}#0`...
--> $DIR/self-in-enum-definition.rs:5:10
|
LL | V3 = Self::V1 {} as u8 + 2,
| ^^^^^^^^
= note: ...which requires computing layout of `Alpha`...
= note: ...which again requires const-evaluating + checking `Alpha::V3::{{constant}}#0`, completing the cycle
note: cycle used when collecting item types in top-level module
--> $DIR/self-in-enum-definition.rs:1:1
|
LL | / #[repr(u8)]
LL | | enum Alpha {
LL | | V1 = 41,
LL | | V2 = Self::V1 as u8 + 1, // OK -- but why?
... |
LL | |
LL | | fn main() {}
| |____________^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0391`.