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Add some helpful comments in trimmed_def_paths.

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To explain things that took me a minute to work out.
This commit is contained in:
Nicholas Nethercote 2024-01-10 10:55:08 +11:00
parent d78329b92e
commit 4efddb141a
1 changed files with 5 additions and 1 deletions
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6
compiler/rustc_middle/src/ty/print/pretty.rs
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@ -3083,7 +3083,8 @@ pub fn trimmed_def_paths(tcx: TyCtxt<'_>, (): ()) -> DefIdMap<Symbol> {
let mut map: DefIdMap<Symbol> = Default::default(); let mut map: DefIdMap<Symbol> = Default::default();
if let TrimmedDefPaths::GoodPath = tcx.sess.opts.trimmed_def_paths { if let TrimmedDefPaths::GoodPath = tcx.sess.opts.trimmed_def_paths {
// Trimming paths is expensive and not optimized, since we expect it to only be used for error reporting. // Trimming paths is expensive and not optimized, since we expect it to only be used for
// error reporting.
// //
// For good paths causing this bug, the `rustc_middle::ty::print::with_no_trimmed_paths` // For good paths causing this bug, the `rustc_middle::ty::print::with_no_trimmed_paths`
// wrapper can be used to suppress this query, in exchange for full paths being formatted. // wrapper can be used to suppress this query, in exchange for full paths being formatted.
@ -3092,6 +3093,8 @@ pub fn trimmed_def_paths(tcx: TyCtxt<'_>, (): ()) -> DefIdMap<Symbol> {
); );
} }
// Once constructed, unique namespace+symbol pairs will have a `Some(_)` entry, while
// non-unique pairs will have a `None` entry.
let unique_symbols_rev: &mut FxHashMap<(Namespace, Symbol), Option<DefId>> = let unique_symbols_rev: &mut FxHashMap<(Namespace, Symbol), Option<DefId>> =
&mut FxHashMap::default(); &mut FxHashMap::default();
@ -3121,6 +3124,7 @@ pub fn trimmed_def_paths(tcx: TyCtxt<'_>, (): ()) -> DefIdMap<Symbol> {
} }
}); });
// Put the symbol from all the unique namespace+symbol pairs into `map`.
for ((_, symbol), opt_def_id) in unique_symbols_rev.drain() { for ((_, symbol), opt_def_id) in unique_symbols_rev.drain() {
use std::collections::hash_map::Entry::{Occupied, Vacant}; use std::collections::hash_map::Entry::{Occupied, Vacant};