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resolve: Add more comments to in-module resolution

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This commit is contained in:
Vadim Petrochenkov 2018-07-20 01:45:08 +03:00
parent 32453db332
commit e7aeb2b1c7
1 changed files with 26 additions and 22 deletions
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48
src/librustc_resolve/resolve_imports.rs
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@ -207,36 +207,39 @@ impl<'a> Resolver<'a> {
}
}
let no_unexpanded_macros = module.unresolved_invocations.borrow().is_empty();
match resolution.binding {
// So we have a resolution that's from a glob import. This resolution is determined
// if it cannot be shadowed by some new item/import expanded from a macro.
// This happens either if there are no unexpanded macros, or expanded names cannot
// shadow globs (that happens in macro namespace or with restricted shadowing).
Some(binding) if no_unexpanded_macros || ns == MacroNS || restricted_shadowing =>
return check_usable(self, binding),
// If we have no resolution, then it's a determined error it some new item/import
// cannot appear from a macro expansion or an undetermined glob.
None if no_unexpanded_macros => {} // go check for globs below
// This is actually an undetermined error, but we need to return determinate error
// due to subtle interactions with `resolve_lexical_macro_path_segment`
// that are going to be removed in the next commit.
None if restricted_shadowing => {} // go check for globs below
_ => return Err(Undetermined),
// So we have a resolution that's from a glob import. This resolution is determined
// if it cannot be shadowed by some new item/import expanded from a macro.
// This happens either if there are no unexpanded macros, or expanded names cannot
// shadow globs (that happens in macro namespace or with restricted shadowing).
let unexpanded_macros = !module.unresolved_invocations.borrow().is_empty();
if let Some(binding) = resolution.binding {
if !unexpanded_macros || ns == MacroNS || restricted_shadowing {
return check_usable(self, binding);
} else {
return Err(Undetermined);
}
}
// --- From now on we have no resolution. ---
// Check if one of glob imports can still define the name,
// if it can then our "no resolution" result is not determined and can be invalidated.
// What on earth is this?
// Apparently one more subtle interaction with `resolve_lexical_macro_path_segment`
// that are going to be removed in the next commit.
// Now we are in situation when new item/import can appear only from a glob or a macro
// expansion. With restricted shadowing names from globs and macro expansions cannot
// shadow names from outer scopes, so we can freely fallback from module search to search
// in outer scopes. To continue search in outer scopes we have to lie a bit and return
// `Determined` to `resolve_lexical_macro_path_segment` even if the correct answer
// for in-module resolution could be `Undetermined`.
if restricted_shadowing {
return Err(Determined);
}
// Check if one of unexpanded macros can still define the name,
// if it can then our "no resolution" result is not determined and can be invalidated.
if unexpanded_macros {
return Err(Undetermined);
}
// Check if one of glob imports can still define the name,
// if it can then our "no resolution" result is not determined and can be invalidated.
for glob_import in module.globs.borrow().iter() {
if !self.is_accessible(glob_import.vis.get()) {
continue
@ -258,6 +261,7 @@ impl<'a> Resolver<'a> {
}
}
// No resolution and no one else can define the name - determinate error.
Err(Determined)
}