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Move variable into the only branch where it is relevant

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At the `if` branch `filter` (the `let` binding) is `None` iff `filter` (the parameter) was `None`.
We can branch on the parameter, move the binding into the `if`, and the complexity of handling
`Option<Option<_>` largely dissolves.
This commit is contained in:
LingMan 2021-01-03 09:19:52 +01:00
parent 18d855b8f6
commit af7134e7de
1 changed files with 7 additions and 8 deletions
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15
compiler/rustc_metadata/src/rmeta/decoder.rs
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@ -1345,15 +1345,14 @@ fn get_implementations_for_trait(
return &[];
}
// Do a reverse lookup beforehand to avoid touching the crate_num
// hash map in the loop below.
let filter = match filter.map(|def_id| self.reverse_translate_def_id(def_id)) {
Some(Some(def_id)) => Some((def_id.krate.as_u32(), def_id.index)),
Some(None) => return &[],
None => None,
};
if let Some(def_id) = filter {
// Do a reverse lookup beforehand to avoid touching the crate_num
// hash map in the loop below.
let filter = match self.reverse_translate_def_id(def_id) {
Some(def_id) => (def_id.krate.as_u32(), def_id.index),
None => return &[],
};
if let Some(filter) = filter {
if let Some(impls) = self.trait_impls.get(&filter) {
tcx.arena.alloc_from_iter(
impls.decode(self).map(|(idx, simplified_self_ty)| {