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Log the output of is_useful in the or-pattern case too

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Nadrieril 2020-12-17 00:47:31 +00:00
parent 7009d20290
commit 170fae2c18
1 changed files with 31 additions and 25 deletions
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56
compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
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@ -904,8 +904,14 @@ fn is_useful<'p, 'tcx>(
assert!(rows.iter().all(|r| r.len() == v.len()));
// FIXME(Nadrieril): Hack to work around type normalization issues (see #72476).
let ty = matrix.heads().next().map(|r| r.ty).unwrap_or(v.head().ty);
let pcx = PatCtxt { cx, matrix, ty, span: v.head().span, is_top_level };
debug!("is_useful_expand_first_col: ty={:#?}, expanding {:#?}", pcx.ty, v.head());
// If the first pattern is an or-pattern, expand it.
if let Some(vs) = v.expand_or_pat() {
let ret = if let Some(vs) = v.expand_or_pat() {
// We expand the or pattern, trying each of its branches in turn and keeping careful track
// of possible unreachable sub-branches.
let mut matrix = matrix.clone();
@ -920,30 +926,30 @@ fn is_useful<'p, 'tcx>(
}
(u, span)
});
return Usefulness::merge(usefulnesses, v.len());
}
// FIXME(Nadrieril): Hack to work around type normalization issues (see #72476).
let ty = matrix.heads().next().map(|r| r.ty).unwrap_or(v.head().ty);
let pcx = PatCtxt { cx, matrix, ty, span: v.head().span, is_top_level };
debug!("is_useful_expand_first_col: ty={:#?}, expanding {:#?}", pcx.ty, v.head());
let ret = v
.head_ctor(cx)
.split(pcx, Some(hir_id))
.into_iter()
.map(|ctor| {
// We cache the result of `Fields::wildcards` because it is used a lot.
let ctor_wild_subpatterns = Fields::wildcards(pcx, &ctor);
let matrix = pcx.matrix.specialize_constructor(pcx, &ctor, &ctor_wild_subpatterns);
let v = v.pop_head_constructor(&ctor_wild_subpatterns);
let usefulness =
is_useful(pcx.cx, &matrix, &v, witness_preference, hir_id, is_under_guard, false);
usefulness.apply_constructor(pcx, &ctor, &ctor_wild_subpatterns)
})
.find(|result| result.is_useful())
.unwrap_or(NotUseful);
Usefulness::merge(usefulnesses, v.len())
} else {
v.head_ctor(cx)
.split(pcx, Some(hir_id))
.into_iter()
.map(|ctor| {
// We cache the result of `Fields::wildcards` because it is used a lot.
let ctor_wild_subpatterns = Fields::wildcards(pcx, &ctor);
let matrix = pcx.matrix.specialize_constructor(pcx, &ctor, &ctor_wild_subpatterns);
let v = v.pop_head_constructor(&ctor_wild_subpatterns);
let usefulness = is_useful(
pcx.cx,
&matrix,
&v,
witness_preference,
hir_id,
is_under_guard,
false,
);
usefulness.apply_constructor(pcx, &ctor, &ctor_wild_subpatterns)
})
.find(|result| result.is_useful())
.unwrap_or(NotUseful)
};
debug!("is_useful::returns({:#?}, {:#?}) = {:?}", matrix, v, ret);
ret
}