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Do MTWT resolution during lowering to HIR #30145

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merged 2 commits into from Dec 9, 2015
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petrochenkov
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Instead of ast::Ident, bindings, paths and labels in HIR now keep a new structure called hir::Ident containing mtwt-renamed name and the original not-renamed unhygienic_name. name is supposed to be used by default, unhygienic_name is rarely used.

This is not ideal, but better than the status quo for two reasons:

  • MTWT tables can be cleared immediately after lowering to HIR
  • This is less bug-prone, because it is impossible now to forget applying mtwt::resolve to a name. It is still possible to use name instead of unhygienic_name by mistake, but unhygienic_names are used only in few very special circumstances, so it shouldn't be a problem.

Besides name resolution unhygienic_name is used in some lints and debuginfo. unhygienic_name can be very well approximated by "reverse renaming" token::intern(name.as_str()) or even plain string name.as_str(), except that it would break gensyms like iter in desugared for loops. This approximation is likely good enough for lints and debuginfo, but not for name resolution, unfortunately (see #27639), so unhygienic_name has to be kept.

cc #29782

r? @nrc

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bors commented Dec 4, 2015

☔ The latest upstream changes (presumably #29850) made this pull request unmergeable. Please resolve the merge conflicts.

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Rebased.


// Discard MTWT tables that aren't required past lowering to HIR.
if !sess.opts.debugging_opts.keep_mtwt_tables &&
!sess.opts.debugging_opts.save_analysis {
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Why does save-analysis need the mtwt tables?

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It calls lower_crate, lowering uses mtwt tables.

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nrc commented Dec 6, 2015

Nice!

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Updated with comments for Ident::from_name and for identifiers in path segments

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nrc commented Dec 7, 2015

@bors: r+

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bors commented Dec 7, 2015

📌 Commit c1d3164 has been approved by nrc

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bors commented Dec 9, 2015

⌛ Testing commit c1d3164 with merge 462ec05...

bors added a commit that referenced this pull request Dec 9, 2015
Instead of `ast::Ident`, bindings, paths and labels in HIR now keep a new structure called `hir::Ident` containing mtwt-renamed `name` and the original not-renamed `unhygienic_name`. `name` is supposed to be used by default, `unhygienic_name` is rarely used.

This is not ideal, but better than the status quo for two reasons:
- MTWT tables can be cleared immediately after lowering to HIR
- This is less bug-prone, because it is impossible now to forget applying `mtwt::resolve` to a name. It is still possible to use `name` instead of `unhygienic_name` by mistake, but `unhygienic_name`s are used only in few very special circumstances, so it shouldn't be a problem.

Besides name resolution `unhygienic_name` is used in some lints and debuginfo. `unhygienic_name` can be very well approximated by "reverse renaming" `token::intern(name.as_str())` or even plain string `name.as_str()`, except that it would break gensyms like `iter` in desugared `for` loops. This approximation is likely good enough for lints and debuginfo, but not for name resolution, unfortunately (see #27639), so `unhygienic_name` has to be kept.

cc #29782

r? @nrc
@bors bors merged commit c1d3164 into rust-lang:master Dec 9, 2015
@petrochenkov petrochenkov mentioned this pull request May 15, 2016
bors added a commit that referenced this pull request May 18, 2016
Remove hir::Ident

Now when name resolution is done on AST, `hir::Ident` is no longer necessary.
See #30145 for more details.

r? @nrc
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4 participants