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fresh binding should shadow the def in expand #143141

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c04da5d
fresh binding should shadow the def after expand
bvanjoi Jul 1, 2025
93887c5
wip: add some test
bvanjoi Aug 17, 2025
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93 changes: 73 additions & 20 deletions compiler/rustc_resolve/src/ident.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,9 +17,9 @@ use crate::late::{ConstantHasGenerics, NoConstantGenericsReason, PathSource, Rib
use crate::macros::{MacroRulesScope, sub_namespace_match};
use crate::{
AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, BindingKey, CmResolver, Determinacy,
Finalize, ImportKind, LexicalScopeBinding, Module, ModuleKind, ModuleOrUniformRoot,
NameBinding, NameBindingKind, ParentScope, PathResult, PrivacyError, Res, ResolutionError,
Resolver, Scope, ScopeSet, Segment, Used, Weak, errors,
Finalize, ImportKind, LexicalScopeBinding, LookaheadItemInBlock, Module, ModuleKind,
ModuleOrUniformRoot, NameBinding, NameBindingKind, ParentScope, PathResult, PrivacyError, Res,
ResolutionError, Resolver, Scope, ScopeSet, Segment, Used, Weak, errors,
};

#[derive(Copy, Clone)]
Expand Down Expand Up @@ -333,20 +333,73 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
*original_rib_ident_def,
ribs,
)));
} else if let RibKind::Block(Some(module)) = rib.kind
&& let Ok(binding) = self.cm().resolve_ident_in_module_unadjusted(
ModuleOrUniformRoot::Module(module),
ident,
ns,
parent_scope,
Shadowing::Unrestricted,
finalize.map(|finalize| Finalize { used: Used::Scope, ..finalize }),
ignore_binding,
None,
)
{
// The ident resolves to an item in a block.
return Some(LexicalScopeBinding::Item(binding));
} else if let RibKind::Block { module, id: block_id } = rib.kind {
if let Some(items) = self.lookahead_items_in_block.get(&block_id) {
let mut expansion = None;
for (node_id, item) in items
.iter()
.rev()
.filter(|(_, item)| matches!(item, LookaheadItemInBlock::MacroDef { .. }))
{
let LookaheadItemInBlock::MacroDef { def_id, bindings, .. } = item else {
unreachable!();
};
if *def_id != self.macro_def(ident.span.ctxt()) {
continue;
}
expansion.get_or_insert(node_id);
ident.span.remove_mark();
if let Some((original_rib_ident_def, res)) = bindings.get_key_value(&ident)
{
// The ident resolves to a type parameter or local variable.
return Some(LexicalScopeBinding::Res(self.validate_res_from_ribs(
i,
ident,
*res,
finalize.map(|finalize| finalize.path_span),
*original_rib_ident_def,
ribs,
)));
}
}
if let Some(expansion) = expansion
&& items.iter().take_while(|(item_id, _)| !expansion.eq(item_id)).any(
|(_, item)| {
if let LookaheadItemInBlock::Binding { name } = item {
name.name == ident.name
} else {
false
}
},
)
{
// return `None` for this case:
//
// ```
// let a = m!();
// let b = 1;
// macro_rules! m { () => { b } }
// use b;
// ```
return None;
}
}

if let Some(module) = module
&& let Ok(binding) = self.cm().resolve_ident_in_module_unadjusted(
ModuleOrUniformRoot::Module(module),
ident,
ns,
parent_scope,
Shadowing::Unrestricted,
finalize.map(|finalize| Finalize { used: Used::Scope, ..finalize }),
ignore_binding,
None,
)
{
// The ident resolves to an item in a block.
return Some(LexicalScopeBinding::Item(binding));
}
} else if let RibKind::Module(module) = rib.kind {
// Encountered a module item, abandon ribs and look into that module and preludes.
return self
Expand Down Expand Up @@ -1166,7 +1219,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
for rib in ribs {
match rib.kind {
RibKind::Normal
| RibKind::Block(..)
| RibKind::Block { .. }
| RibKind::FnOrCoroutine
| RibKind::Module(..)
| RibKind::MacroDefinition(..)
Expand Down Expand Up @@ -1259,7 +1312,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
for rib in ribs {
let (has_generic_params, def_kind) = match rib.kind {
RibKind::Normal
| RibKind::Block(..)
| RibKind::Block { .. }
| RibKind::FnOrCoroutine
| RibKind::Module(..)
| RibKind::MacroDefinition(..)
Expand Down Expand Up @@ -1353,7 +1406,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
for rib in ribs {
let (has_generic_params, def_kind) = match rib.kind {
RibKind::Normal
| RibKind::Block(..)
| RibKind::Block { .. }
| RibKind::FnOrCoroutine
| RibKind::Module(..)
| RibKind::MacroDefinition(..)
Expand Down
126 changes: 111 additions & 15 deletions compiler/rustc_resolve/src/late.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -39,9 +39,9 @@ use thin_vec::ThinVec;
use tracing::{debug, instrument, trace};

use crate::{
BindingError, BindingKey, Finalize, LexicalScopeBinding, Module, ModuleOrUniformRoot,
NameBinding, ParentScope, PathResult, ResolutionError, Resolver, Segment, TyCtxt, UseError,
Used, errors, path_names_to_string, rustdoc,
BindingError, BindingKey, Finalize, LexicalScopeBinding, LookaheadItemInBlock, Module,
ModuleOrUniformRoot, NameBinding, ParentScope, PathResult, ResolutionError, Resolver, Segment,
TyCtxt, UseError, Used, errors, path_names_to_string, rustdoc,
};

mod diagnostics;
Expand Down Expand Up @@ -102,7 +102,7 @@ impl IntoDiagArg for PatternSource {
/// Denotes whether the context for the set of already bound bindings is a `Product`
/// or `Or` context. This is used in e.g., `fresh_binding` and `resolve_pattern_inner`.
/// See those functions for more information.
#[derive(PartialEq)]
#[derive(PartialEq, Debug)]
enum PatBoundCtx {
/// A product pattern context, e.g., `Variant(a, b)`.
Product,
Expand Down Expand Up @@ -197,7 +197,29 @@ pub(crate) enum RibKind<'ra> {
/// `Block(None)` must be always processed in the same way as `Block(Some(module))`
/// with empty `module`. The module can be `None` only because creation of some definitely
/// empty modules is skipped as an optimization.
Block(Option<Module<'ra>>),
Block {
module: Option<Module<'ra>>,
/// The node id of block kind, which stores all bindings defined in
/// this local scope, for these features:
///
/// - Forward reference detection:
///
/// ```ignore (illustrative)
/// let a = b; // displays '`b` is defined at <span>' instead of ''b' not found'
/// let b = 42;
/// ```
///
/// - Correctly resolves the hoisting bindings within macro expand:
///
/// ```ignore (illustrative)
/// fn f() {}
/// let a: i16 = m!(); // throw error because it should use the local `f` rather than `fn f`
/// let f = || -> i16 { 42 };
/// macro_rules! m {() => ( f() )}
/// use m;
/// ```
id: NodeId,
},

/// We passed through an impl or trait and are now in one of its
/// methods or associated types. Allow references to ty params that impl or trait
Expand Down Expand Up @@ -249,7 +271,7 @@ impl RibKind<'_> {
pub(crate) fn contains_params(&self) -> bool {
match self {
RibKind::Normal
| RibKind::Block(..)
| RibKind::Block { .. }
| RibKind::FnOrCoroutine
| RibKind::ConstantItem(..)
| RibKind::Module(_)
Expand Down Expand Up @@ -2816,7 +2838,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
for parent_rib in self.ribs[ns].iter().rev() {
// Break at module or block level, to account for nested items which are
// allowed to shadow generic param names.
if matches!(parent_rib.kind, RibKind::Module(..) | RibKind::Block(..)) {
if matches!(parent_rib.kind, RibKind::Module(..) | RibKind::Block { .. }) {
break;
}

Expand Down Expand Up @@ -3769,6 +3791,52 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
fn resolve_pattern_top(&mut self, pat: &'ast Pat, pat_src: PatternSource) {
let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
self.resolve_pattern(pat, pat_src, &mut bindings);

let mut last_pat_id = None;
pat.walk(&mut |pat| {
if let PatKind::Ident(..) = pat.kind {
last_pat_id = Some(pat.id);
}
true
});

if let Some(last_pat_id) = last_pat_id
&& let RibKind::Block { id: block, .. } = self.ribs[ValueNS].last_mut().unwrap().kind
&& let Some(items) = self.r.lookahead_items_in_block.get_mut(&block)
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So, in

let a = 0;
{
  let b = 1;
  macro_rules! m { ... }
}

only b will be added to LookaheadItemInBlock::MacroDef bindings for m, but not a.

Is this ok?
If yes, why is this ok?

{
let start = items.get_index_of(&last_pat_id).unwrap_or_else(|| {
panic!("pattern({pat:#?}) not found in lookahead items");
});
// let mut first_macro: Option<SyntaxContext> = None;
// `need_removed` used for avoid injecting masked names into macro definition bindings:
//
// ```
// let x = 0;
// macro_rules! m0 {() => { x; }} // Injects `let x = 0` into `m0`
// let x = 1;
// macro_rules! m1 {() => { x; }} // Should NOT inject `let x = 0` into `m1`
// ```
let mut need_removed = FxHashSet::default();
for (_, item) in items.iter_mut().skip(start + 1) {
match item {
LookaheadItemInBlock::Binding { name } => {
need_removed.insert(name.normalize_to_macro_rules());
}
LookaheadItemInBlock::MacroDef { bindings: macro_bindings, .. } => {
let bindings =
bindings.last().unwrap().1.iter().filter_map(|(name, res)| {
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Suggested change
bindings.last().unwrap().1.iter().filter_map(|(name, res)| {
bindings.last().unwrap().1.iter().copied().filter(|(name, _)| !need_removed.contains(name))

if !need_removed.contains(&name) {
Some((*name, *res))
} else {
None
}
});
macro_bindings.extend(bindings);
}
}
}
}

self.apply_pattern_bindings(bindings);
}

Expand Down Expand Up @@ -4650,11 +4718,12 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
let mut num_macro_definition_ribs = 0;
if let Some(anonymous_module) = anonymous_module {
debug!("(resolving block) found anonymous module, moving down");
self.ribs[ValueNS].push(Rib::new(RibKind::Block(Some(anonymous_module))));
self.ribs[TypeNS].push(Rib::new(RibKind::Block(Some(anonymous_module))));
let rib_kind = RibKind::Block { module: Some(anonymous_module), id: block.id };
self.ribs[ValueNS].push(Rib::new(rib_kind));
self.ribs[TypeNS].push(Rib::new(rib_kind));
self.parent_scope.module = anonymous_module;
} else {
self.ribs[ValueNS].push(Rib::new(RibKind::Block(None)));
self.ribs[ValueNS].push(Rib::new(RibKind::Block { module: None, id: block.id }));
}

// Descend into the block.
Expand All @@ -4664,7 +4733,6 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
{
num_macro_definition_ribs += 1;
let res = self.r.local_def_id(item.id).to_def_id();
self.ribs[ValueNS].push(Rib::new(RibKind::MacroDefinition(res)));
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I think we can remove RibKind::MacroDefinition in the future since all macro bindings can be accessed through RibKind::Block.

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If the new scheme is already implemented, then it's better to remove it now to make sure everything is migrated correctly.

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I see, it's still there due to labels, but labels are supposed to be resolved just like local variables, so they can migrate to the new scheme too.

self.label_ribs.push(Rib::new(RibKind::MacroDefinition(res)));
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Labels have the same hygiene as local variables and are also resolved at macro definition site.

}

Expand All @@ -4674,7 +4742,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
// Move back up.
self.parent_scope.module = orig_module;
for _ in 0..num_macro_definition_ribs {
self.ribs[ValueNS].pop();
// pop `MacroDefinition`
self.label_ribs.pop();
}
self.last_block_rib = self.ribs[ValueNS].pop();
Expand Down Expand Up @@ -5134,6 +5202,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
/// lifetime generic parameters and function parameters.
struct ItemInfoCollector<'a, 'ra, 'tcx> {
r: &'a mut Resolver<'ra, 'tcx>,
current_block: Option<NodeId>,
}

impl ItemInfoCollector<'_, '_, '_> {
Expand Down Expand Up @@ -5189,12 +5258,20 @@ impl<'ast> Visitor<'ast> for ItemInfoCollector<'_, '_, '_> {
}
}
}

ItemKind::MacroDef(_, _) => {
if let Some(block_id) = self.current_block {
let def_id = self.r.local_def_id(item.id).to_def_id();
let items = self.r.lookahead_items_in_block.entry(block_id).or_default();
items.insert(
item.id,
LookaheadItemInBlock::MacroDef { bindings: Default::default(), def_id },
);
}
}
ItemKind::Mod(..)
| ItemKind::Static(..)
| ItemKind::Use(..)
| ItemKind::ExternCrate(..)
| ItemKind::MacroDef(..)
| ItemKind::GlobalAsm(..)
| ItemKind::MacCall(..)
| ItemKind::DelegationMac(..) => {}
Expand All @@ -5214,11 +5291,30 @@ impl<'ast> Visitor<'ast> for ItemInfoCollector<'_, '_, '_> {
}
visit::walk_assoc_item(self, item, ctxt);
}

fn visit_local(&mut self, node: &'ast Local) -> Self::Result {
// collect local bindings into block
node.pat.walk(&mut |pat| {
if let PatKind::Ident(_, name, _) = &pat.kind {
let block_id = self.current_block.unwrap();
let items = self.r.lookahead_items_in_block.entry(block_id).or_default();
items.insert(pat.id, LookaheadItemInBlock::Binding { name: *name });
}
true
});
visit::walk_local(self, node)
}

fn visit_block(&mut self, node: &'ast Block) -> Self::Result {
let saved_block_id = self.current_block.replace(node.id);
visit::walk_block(self, node);
self.current_block = saved_block_id;
}
}

impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
pub(crate) fn late_resolve_crate(&mut self, krate: &Crate) {
visit::walk_crate(&mut ItemInfoCollector { r: self }, krate);
visit::walk_crate(&mut ItemInfoCollector { r: self, current_block: None }, krate);
let mut late_resolution_visitor = LateResolutionVisitor::new(self);
late_resolution_visitor.resolve_doc_links(&krate.attrs, MaybeExported::Ok(CRATE_NODE_ID));
visit::walk_crate(&mut late_resolution_visitor, krate);
Expand Down
15 changes: 4 additions & 11 deletions compiler/rustc_resolve/src/late/diagnostics.rs
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Expand Up @@ -898,7 +898,8 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
if path.len() == 1 {
for rib in self.ribs[ns].iter().rev() {
let item = path[0].ident;
if let RibKind::Module(module) | RibKind::Block(Some(module)) = rib.kind
if let RibKind::Module(module) | RibKind::Block { module: Some(module), .. } =
rib.kind
&& let Some(did) = find_doc_alias_name(self.r, module, item.name)
{
return Some((did, item));
Expand Down Expand Up @@ -2438,7 +2439,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
) -> TypoCandidate {
let mut names = Vec::new();
if let [segment] = path {
let mut ctxt = segment.ident.span.ctxt();
let ctxt = segment.ident.span.ctxt();

// Search in lexical scope.
// Walk backwards up the ribs in scope and collect candidates.
Expand All @@ -2456,7 +2457,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
}
}

if let RibKind::Block(Some(module)) = rib.kind {
if let RibKind::Block { module: Some(module), .. } = rib.kind {
self.r.add_module_candidates(module, &mut names, &filter_fn, Some(ctxt));
} else if let RibKind::Module(module) = rib.kind {
// Encountered a module item, abandon ribs and look into that module and preludes.
Expand All @@ -2469,14 +2470,6 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
);
break;
}

if let RibKind::MacroDefinition(def) = rib.kind
&& def == self.r.macro_def(ctxt)
{
// If an invocation of this macro created `ident`, give up on `ident`
// and switch to `ident`'s source from the macro definition.
ctxt.remove_mark();
}
}
} else {
// Search in module.
Expand Down
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