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resolve: use #[doc(alias)] to improve function resolution diagnostics #154833

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resolve: use #[doc(alias)] to improve function resolution diagnostics #154833

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52 changes: 52 additions & 0 deletions compiler/rustc_resolve/src/build_reduced_graph.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ use rustc_ast::{
};
use rustc_attr_parsing as attr;
use rustc_attr_parsing::AttributeParser;
use rustc_data_structures::fx::FxHashSet;
use rustc_expand::base::ResolverExpand;
use rustc_expand::expand::AstFragment;
use rustc_hir::Attribute;
Expand Down Expand Up @@ -569,6 +570,52 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
}
}

/// Extracts `#[doc(alias = "...")]` and `#[doc(alias(...))]` from attributes.
///
/// Uses a lightweight, ad-hoc approach instead of the full attribute parsing
/// machinery to collect aliases for later use in diagnostics.
fn parse_doc_aliases(&self, attrs: &[ast::Attribute]) -> FxHashSet<Symbol> {
let mut aliases = FxHashSet::default();

for attr in attrs {
if !attr.has_name(sym::doc) {
continue;
}

// Get #[doc(...)] list
let Some(items) = attr.meta_item_list() else {
continue;
};

for item in items {
let Some(meta) = item.meta_item() else {
continue;
};

if !meta.has_name(sym::alias) {
continue;
}

// Case 1: #[doc(alias = "foo")]
if let Some(value) = meta.value_str() {
aliases.insert(value);
continue;
}

// Case 2: #[doc(alias("foo", "bar"))]
if let Some(nested) = meta.meta_item_list() {
for nested_item in nested {
if let Some(lit) = nested_item.lit() {
aliases.insert(lit.symbol);
}
}
}
}
}

aliases
}

fn build_reduced_graph_for_use_tree(
&mut self,
// This particular use tree
Expand Down Expand Up @@ -875,6 +922,11 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
ItemKind::Fn(box Fn { ident, .. }) => {
self.r.define_local(parent, ident, ValueNS, res, vis, sp, expansion);

if !item.attrs.is_empty() {
// for better error reporting in doc alias for function
let aliases = self.parse_doc_aliases(&item.attrs);
self.r.doc_aliases.insert(local_def_id, aliases);
}
// Functions introducing procedural macros reserve a slot
// in the macro namespace as well (see #52225).
self.define_macro(item);
Expand Down
13 changes: 8 additions & 5 deletions compiler/rustc_resolve/src/late/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1112,11 +1112,14 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
else {
continue;
};
if did.is_local() {
// We don't record the doc alias name in the local crate
// because the people who write doc alias are usually not
// confused by them.
continue;
if let Some(local) = did.as_local() {
if let Some(aliases) = r.doc_aliases.get(&local)
&& aliases.contains(&item_name)
{
return Some(did);
} else {
continue;
}
}
if let Some(d) = hir::find_attr!(r.tcx, did, Doc(d) => d)
&& d.aliases.contains_key(&item_name)
Expand Down
3 changes: 3 additions & 0 deletions compiler/rustc_resolve/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1404,6 +1404,9 @@ pub struct Resolver<'ra, 'tcx> {

mods_with_parse_errors: FxHashSet<DefId> = default::fx_hash_set(),

// for better error reporting in doc alias for function
doc_aliases: FxHashMap<LocalDefId, FxHashSet<Symbol>> = default::fx_hash_map(),

/// Whether `Resolver::register_macros_for_all_crates` has been called once already, as we
/// don't need to run it more than once.
all_crate_macros_already_registered: bool = false,
Expand Down
33 changes: 33 additions & 0 deletions tests/ui/attributes/doc-alias-attr.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
#[doc(alias = "bar")]
fn foo() {}

#[doc(alias("sum", "plus"))]
fn net() {}

struct S;

impl S {
#[doc(alias("bar"))]
fn foo() {}

#[doc(alias= "baz")]
fn qux(&self, x: i32) {}
}


fn main() {
S::bar();
//~^ ERROR no associated function or constant named `bar` found for struct `S` in the current scope
//~| HELP there is an associated function `foo` with a similar name

let s = S;
s.baz(10);
//~^ ERROR no method named `baz`
//~| HELP there is a method `qux` with a similar name

sum(); //~ ERROR: cannot find function `sum` in this scope
//~| HELP: `net` has a name defined in the doc alias attribute as `sum`

bar(); //~ ERROR: cannot find function `bar` in this scope
//~| HELP: `foo` has a name defined in the doc alias attribute as `bar`
}
58 changes: 58 additions & 0 deletions tests/ui/attributes/doc-alias-attr.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,58 @@
error[E0599]: no associated function or constant named `bar` found for struct `S` in the current scope
--> $DIR/doc-alias-attr.rs:19:8
|
LL | struct S;
| -------- associated function or constant `bar` not found for this struct
...
LL | S::bar();
| ^^^ associated function or constant not found in `S`
|
help: there is an associated function `foo` with a similar name
|
LL - S::bar();
LL + S::foo();
|

error[E0599]: no method named `baz` found for struct `S` in the current scope
--> $DIR/doc-alias-attr.rs:24:7
|
LL | struct S;
| -------- method `baz` not found for this struct
...
LL | s.baz(10);
| ^^^
|
help: there is a method `qux` with a similar name
|
LL - s.baz(10);
LL + s.qux(10);
|

error[E0425]: cannot find function `sum` in this scope
--> $DIR/doc-alias-attr.rs:28:5
|
LL | sum();
| ^^^
|
help: `net` has a name defined in the doc alias attribute as `sum`
|
LL - sum();
LL + net();
|

error[E0425]: cannot find function `bar` in this scope
--> $DIR/doc-alias-attr.rs:31:5
|
LL | bar();
| ^^^
|
help: `foo` has a name defined in the doc alias attribute as `bar`
|
LL - bar();
LL + foo();
|

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0425, E0599.
For more information about an error, try `rustc --explain E0425`.
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