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Consider compiler-erroring instead of panicking in DST APIs #1149

Closed
Tracked by #671
jswrenn opened this issue Apr 29, 2024 · 1 comment · Fixed by #1154
Closed
Tracked by #671

Consider compiler-erroring instead of panicking in DST APIs #1149

jswrenn opened this issue Apr 29, 2024 · 1 comment · Fixed by #1154

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@jswrenn
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jswrenn commented Apr 29, 2024 •
edited by joshlf
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This issue goes partway towards addressing #325.

For example, Ref::from_prefix_with_trailing_elements documents a panic if Self is a ZST. However, the ZST-iness (pronounced "zestiness") of a type relevant here is always a static property and can be reported via postmonomorphization error.

The advantages of this are several-fold:

  • it allows us to maintain the consistent policy that our APIs do not panic (with the exception of panics in user-supplied TryFromBytes validators)
  • it is forwards compatible with us relaxing the compile error to a panic in future non-breaking releases
  • it may have optimizer advantages

Postmonomorphization errors currently have a bit of a 'weirdness' factor (and an unwieldy name), but I suspect that will change. The recent stabilization notes for inline const exprs cite ZST-checking as a motivating case of what the feature will make possible.
@jswrenn jswrenn mentioned this issue Apr 29, 2024
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joshlf commented Apr 29, 2024

Note that this partially addresses #325. I think we should leave #325 open and continue the main discussion there, but it's good to have this as a separate issue so we can block #671 on it.

@joshlf joshlf mentioned this issue Apr 29, 2024
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@jswrenn jswrenn mentioned this issue Apr 30, 2024
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jswrenn added a commit that referenced this issue May 1, 2024
@jswrenn
Use compile-time assertions to deny ZSTy DSTs
e4c0450 
Presently, we deny ZSTy DSTs in our APIs via panicking at runtime. However, the
ZSTiness of a DST is statically detectable and can be denied instead at compile
time. This PR replaces our ZSTy DST panics with compile-time assertions. Doing
gives us the freedom later provide meaningful runtime semantics in such cases.

Partially addresses #325
Closes #1149
jswrenn added a commit that referenced this issue May 1, 2024
@jswrenn
Use compile-time assertions to deny ZSTy DSTs
0b22ac7 
Presently, we deny ZSTy DSTs in our APIs via panicking at runtime. However, the
ZSTiness of a DST is statically detectable and can be denied instead at compile
time. This PR replaces our ZSTy DST panics with compile-time assertions. Doing
gives us the freedom later provide meaningful runtime semantics in such cases.

Partially addresses #325
Closes #1149
jswrenn added a commit that referenced this issue May 1, 2024
@jswrenn
Use compile-time assertions to deny ZSTy DSTs
d3c2576 
Presently, we deny ZSTy DSTs in our APIs via panicking at runtime. However, the
ZSTiness of a DST is statically detectable and can be denied instead at compile
time. This PR replaces our ZSTy DST panics with compile-time assertions. Doing
gives us the freedom later provide meaningful runtime semantics in such cases.

Partially addresses #325
Closes #1149
joshlf pushed a commit that referenced this issue May 1, 2024
@jswrenn @joshlf
Use compile-time assertions to deny ZSTy DSTs
03d13f9 
Presently, we deny ZSTy DSTs in our APIs via panicking at runtime. However, the
ZSTiness of a DST is statically detectable and can be denied instead at compile
time. This PR replaces our ZSTy DST panics with compile-time assertions. Doing
gives us the freedom later provide meaningful runtime semantics in such cases.

Partially addresses #325
Closes #1149
github-merge-queue bot pushed a commit that referenced this issue May 1, 2024
@jswrenn
Use compile-time assertions to deny ZSTy DSTs (#1154)
fb51cad 
Presently, we deny ZSTy DSTs in our APIs via panicking at runtime. However, the
ZSTiness of a DST is statically detectable and can be denied instead at compile
time. This PR replaces our ZSTy DST panics with compile-time assertions. Doing
gives us the freedom later provide meaningful runtime semantics in such cases.

Partially addresses #325
Closes #1149
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Use compile-time assertions to deny ZSTy DSTs google/zerocopy
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