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@Centril @petrochenkov @jakubadamw @matthewjasper @Mark-Simulacrum
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//! "Late resolution" is the pass that resolves most of names in a crate beside imports and macros.
//! It runs when the crate is fully expanded and its module structure is fully built.
//! So it just walks through the crate and resolves all the expressions, types, etc.
//!
//! If you wonder why there's no `early.rs`, that's because it's split into three files -
//! `build_reduced_graph.rs`, `macros.rs` and `resolve_imports.rs`.
use GenericParameters::*;
use RibKind::*;
use crate::{path_names_to_string, BindingError, CrateLint, LexicalScopeBinding};
use crate::{Module, ModuleOrUniformRoot, NameBindingKind, ParentScope, PathResult};
use crate::{ResolutionError, Resolver, Segment, UseError};
use log::debug;
use rustc::{bug, lint, span_bug};
use rustc::hir::def::{self, PartialRes, DefKind, CtorKind, PerNS};
use rustc::hir::def::Namespace::{self, *};
use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX};
use rustc::hir::TraitCandidate;
use rustc::util::nodemap::{FxHashMap, FxHashSet};
use smallvec::{smallvec, SmallVec};
use syntax::{unwrap_or, walk_list};
use syntax::ast::*;
use syntax::ptr::P;
use syntax::symbol::{kw, sym};
use syntax::util::lev_distance::find_best_match_for_name;
use syntax::visit::{self, Visitor, FnKind};
use syntax_pos::Span;
use std::collections::BTreeSet;
use std::mem::replace;
mod diagnostics;
type Res = def::Res<NodeId>;
type IdentMap<T> = FxHashMap<Ident, T>;
/// Map from the name in a pattern to its binding mode.
type BindingMap = IdentMap<BindingInfo>;
#[derive(Copy, Clone, Debug)]
struct BindingInfo {
span: Span,
binding_mode: BindingMode,
}
#[derive(Copy, Clone)]
enum GenericParameters<'a, 'b> {
NoGenericParams,
HasGenericParams(// Type parameters.
&'b Generics,
// The kind of the rib used for type parameters.
RibKind<'a>),
}
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
enum PatternSource {
Match,
Let,
For,
FnParam,
}
impl PatternSource {
fn descr(self) -> &'static str {
match self {
PatternSource::Match => "match binding",
PatternSource::Let => "let binding",
PatternSource::For => "for binding",
PatternSource::FnParam => "function parameter",
}
}
}
/// 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.
enum PatBoundCtx {
/// A product pattern context, e.g., `Variant(a, b)`.
Product,
/// An or-pattern context, e.g., `p_0 | ... | p_n`.
Or,
}
/// The rib kind restricts certain accesses,
/// e.g. to a `Res::Local` of an outer item.
#[derive(Copy, Clone, Debug)]
crate enum RibKind<'a> {
/// No restriction needs to be applied.
NormalRibKind,
/// 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
/// binds. Disallow any other upvars (including other ty params that are
/// upvars).
AssocItemRibKind,
/// We passed through a function definition. Disallow upvars.
/// Permit only those const parameters that are specified in the function's generics.
FnItemRibKind,
/// We passed through an item scope. Disallow upvars.
ItemRibKind,
/// We're in a constant item. Can't refer to dynamic stuff.
ConstantItemRibKind,
/// We passed through a module.
ModuleRibKind(Module<'a>),
/// We passed through a `macro_rules!` statement
MacroDefinition(DefId),
/// All bindings in this rib are type parameters that can't be used
/// from the default of a type parameter because they're not declared
/// before said type parameter. Also see the `visit_generics` override.
ForwardTyParamBanRibKind,
/// We forbid the use of type parameters as the types of const parameters.
TyParamAsConstParamTy,
}
impl RibKind<'_> {
// Whether this rib kind contains generic parameters, as opposed to local
// variables.
crate fn contains_params(&self) -> bool {
match self {
NormalRibKind
| FnItemRibKind
| ConstantItemRibKind
| ModuleRibKind(_)
| MacroDefinition(_) => false,
AssocItemRibKind
| ItemRibKind
| ForwardTyParamBanRibKind
| TyParamAsConstParamTy => true,
}
}
}
/// A single local scope.
///
/// A rib represents a scope names can live in. Note that these appear in many places, not just
/// around braces. At any place where the list of accessible names (of the given namespace)
/// changes or a new restrictions on the name accessibility are introduced, a new rib is put onto a
/// stack. This may be, for example, a `let` statement (because it introduces variables), a macro,
/// etc.
///
/// Different [rib kinds](enum.RibKind) are transparent for different names.
///
/// The resolution keeps a separate stack of ribs as it traverses the AST for each namespace. When
/// resolving, the name is looked up from inside out.
#[derive(Debug)]
crate struct Rib<'a, R = Res> {
pub bindings: IdentMap<R>,
pub kind: RibKind<'a>,
}
impl<'a, R> Rib<'a, R> {
fn new(kind: RibKind<'a>) -> Rib<'a, R> {
Rib {
bindings: Default::default(),
kind,
}
}
}
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
crate enum AliasPossibility {
No,
Maybe,
}
#[derive(Copy, Clone, Debug)]
crate enum PathSource<'a> {
// Type paths `Path`.
Type,
// Trait paths in bounds or impls.
Trait(AliasPossibility),
// Expression paths `path`, with optional parent context.
Expr(Option<&'a Expr>),
// Paths in path patterns `Path`.
Pat,
// Paths in struct expressions and patterns `Path { .. }`.
Struct,
// Paths in tuple struct patterns `Path(..)`.
TupleStruct,
// `m::A::B` in `<T as m::A>::B::C`.
TraitItem(Namespace),
}
impl<'a> PathSource<'a> {
fn namespace(self) -> Namespace {
match self {
PathSource::Type | PathSource::Trait(_) | PathSource::Struct => TypeNS,
PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct => ValueNS,
PathSource::TraitItem(ns) => ns,
}
}
fn defer_to_typeck(self) -> bool {
match self {
PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
PathSource::Struct | PathSource::TupleStruct => true,
PathSource::Trait(_) | PathSource::TraitItem(..) => false,
}
}
fn descr_expected(self) -> &'static str {
match self {
PathSource::Type => "type",
PathSource::Trait(_) => "trait",
PathSource::Pat => "unit struct/variant or constant",
PathSource::Struct => "struct, variant or union type",
PathSource::TupleStruct => "tuple struct/variant",
PathSource::TraitItem(ns) => match ns {
TypeNS => "associated type",
ValueNS => "method or associated constant",
MacroNS => bug!("associated macro"),
},
PathSource::Expr(parent) => match parent.map(|p| &p.node) {
// "function" here means "anything callable" rather than `DefKind::Fn`,
// this is not precise but usually more helpful than just "value".
Some(&ExprKind::Call(..)) => "function",
_ => "value",
},
}
}
crate fn is_expected(self, res: Res) -> bool {
match self {
PathSource::Type => match res {
Res::Def(DefKind::Struct, _)
| Res::Def(DefKind::Union, _)
| Res::Def(DefKind::Enum, _)
| Res::Def(DefKind::Trait, _)
| Res::Def(DefKind::TraitAlias, _)
| Res::Def(DefKind::TyAlias, _)
| Res::Def(DefKind::AssocTy, _)
| Res::PrimTy(..)
| Res::Def(DefKind::TyParam, _)
| Res::SelfTy(..)
| Res::Def(DefKind::OpaqueTy, _)
| Res::Def(DefKind::ForeignTy, _) => true,
_ => false,
},
PathSource::Trait(AliasPossibility::No) => match res {
Res::Def(DefKind::Trait, _) => true,
_ => false,
},
PathSource::Trait(AliasPossibility::Maybe) => match res {
Res::Def(DefKind::Trait, _) => true,
Res::Def(DefKind::TraitAlias, _) => true,
_ => false,
},
PathSource::Expr(..) => match res {
Res::Def(DefKind::Ctor(_, CtorKind::Const), _)
| Res::Def(DefKind::Ctor(_, CtorKind::Fn), _)
| Res::Def(DefKind::Const, _)
| Res::Def(DefKind::Static, _)
| Res::Local(..)
| Res::Def(DefKind::Fn, _)
| Res::Def(DefKind::Method, _)
| Res::Def(DefKind::AssocConst, _)
| Res::SelfCtor(..)
| Res::Def(DefKind::ConstParam, _) => true,
_ => false,
},
PathSource::Pat => match res {
Res::Def(DefKind::Ctor(_, CtorKind::Const), _) |
Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) |
Res::SelfCtor(..) => true,
_ => false,
},
PathSource::TupleStruct => match res {
Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) | Res::SelfCtor(..) => true,
_ => false,
},
PathSource::Struct => match res {
Res::Def(DefKind::Struct, _)
| Res::Def(DefKind::Union, _)
| Res::Def(DefKind::Variant, _)
| Res::Def(DefKind::TyAlias, _)
| Res::Def(DefKind::AssocTy, _)
| Res::SelfTy(..) => true,
_ => false,
},
PathSource::TraitItem(ns) => match res {
Res::Def(DefKind::AssocConst, _)
| Res::Def(DefKind::Method, _) if ns == ValueNS => true,
Res::Def(DefKind::AssocTy, _) if ns == TypeNS => true,
_ => false,
},
}
}
fn error_code(self, has_unexpected_resolution: bool) -> &'static str {
syntax::diagnostic_used!(E0404);
syntax::diagnostic_used!(E0405);
syntax::diagnostic_used!(E0412);
syntax::diagnostic_used!(E0422);
syntax::diagnostic_used!(E0423);
syntax::diagnostic_used!(E0425);
syntax::diagnostic_used!(E0531);
syntax::diagnostic_used!(E0532);
syntax::diagnostic_used!(E0573);
syntax::diagnostic_used!(E0574);
syntax::diagnostic_used!(E0575);
syntax::diagnostic_used!(E0576);
match (self, has_unexpected_resolution) {
(PathSource::Trait(_), true) => "E0404",
(PathSource::Trait(_), false) => "E0405",
(PathSource::Type, true) => "E0573",
(PathSource::Type, false) => "E0412",
(PathSource::Struct, true) => "E0574",
(PathSource::Struct, false) => "E0422",
(PathSource::Expr(..), true) => "E0423",
(PathSource::Expr(..), false) => "E0425",
(PathSource::Pat, true) | (PathSource::TupleStruct, true) => "E0532",
(PathSource::Pat, false) | (PathSource::TupleStruct, false) => "E0531",
(PathSource::TraitItem(..), true) => "E0575",
(PathSource::TraitItem(..), false) => "E0576",
}
}
}
struct LateResolutionVisitor<'a, 'b> {
r: &'b mut Resolver<'a>,
/// The module that represents the current item scope.
parent_scope: ParentScope<'a>,
/// The current set of local scopes for types and values.
/// FIXME #4948: Reuse ribs to avoid allocation.
ribs: PerNS<Vec<Rib<'a>>>,
/// The current set of local scopes, for labels.
label_ribs: Vec<Rib<'a, NodeId>>,
/// The trait that the current context can refer to.
current_trait_ref: Option<(Module<'a>, TraitRef)>,
/// The current trait's associated types' ident, used for diagnostic suggestions.
current_trait_assoc_types: Vec<Ident>,
/// The current self type if inside an impl (used for better errors).
current_self_type: Option<Ty>,
/// The current self item if inside an ADT (used for better errors).
current_self_item: Option<NodeId>,
/// A list of labels as of yet unused. Labels will be removed from this map when
/// they are used (in a `break` or `continue` statement)
unused_labels: FxHashMap<NodeId, Span>,
/// Only used for better errors on `fn(): fn()`.
current_type_ascription: Vec<Span>,
}
/// Walks the whole crate in DFS order, visiting each item, resolving names as it goes.
impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> {
fn visit_item(&mut self, item: &'tcx Item) {
self.resolve_item(item);
}
fn visit_arm(&mut self, arm: &'tcx Arm) {
self.resolve_arm(arm);
}
fn visit_block(&mut self, block: &'tcx Block) {
self.resolve_block(block);
}
fn visit_anon_const(&mut self, constant: &'tcx AnonConst) {
debug!("visit_anon_const {:?}", constant);
self.with_constant_rib(|this| {
visit::walk_anon_const(this, constant);
});
}
fn visit_expr(&mut self, expr: &'tcx Expr) {
self.resolve_expr(expr, None);
}
fn visit_local(&mut self, local: &'tcx Local) {
self.resolve_local(local);
}
fn visit_ty(&mut self, ty: &'tcx Ty) {
match ty.node {
TyKind::Path(ref qself, ref path) => {
self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
}
TyKind::ImplicitSelf => {
let self_ty = Ident::with_dummy_span(kw::SelfUpper);
let res = self.resolve_ident_in_lexical_scope(self_ty, TypeNS, Some(ty.id), ty.span)
.map_or(Res::Err, |d| d.res());
self.r.record_partial_res(ty.id, PartialRes::new(res));
}
_ => (),
}
visit::walk_ty(self, ty);
}
fn visit_poly_trait_ref(&mut self,
tref: &'tcx PolyTraitRef,
m: &'tcx TraitBoundModifier) {
self.smart_resolve_path(tref.trait_ref.ref_id, None,
&tref.trait_ref.path, PathSource::Trait(AliasPossibility::Maybe));
visit::walk_poly_trait_ref(self, tref, m);
}
fn visit_foreign_item(&mut self, foreign_item: &'tcx ForeignItem) {
let generic_params = match foreign_item.node {
ForeignItemKind::Fn(_, ref generics) => {
HasGenericParams(generics, ItemRibKind)
}
ForeignItemKind::Static(..) => NoGenericParams,
ForeignItemKind::Ty => NoGenericParams,
ForeignItemKind::Macro(..) => NoGenericParams,
};
self.with_generic_param_rib(generic_params, |this| {
visit::walk_foreign_item(this, foreign_item);
});
}
fn visit_fn(&mut self, fn_kind: FnKind<'tcx>, declaration: &'tcx FnDecl, _: Span, _: NodeId) {
debug!("(resolving function) entering function");
let rib_kind = match fn_kind {
FnKind::ItemFn(..) => FnItemRibKind,
FnKind::Method(..) | FnKind::Closure(_) => NormalRibKind,
};
// Create a value rib for the function.
self.with_rib(ValueNS, rib_kind, |this| {
// Create a label rib for the function.
this.with_label_rib(rib_kind, |this| {
// Add each argument to the rib.
this.resolve_params(&declaration.inputs);
visit::walk_fn_ret_ty(this, &declaration.output);
// Resolve the function body, potentially inside the body of an async closure
match fn_kind {
FnKind::ItemFn(.., body) |
FnKind::Method(.., body) => this.visit_block(body),
FnKind::Closure(body) => this.visit_expr(body),
};
debug!("(resolving function) leaving function");
})
});
}
fn visit_generics(&mut self, generics: &'tcx Generics) {
// For type parameter defaults, we have to ban access
// to following type parameters, as the InternalSubsts can only
// provide previous type parameters as they're built. We
// put all the parameters on the ban list and then remove
// them one by one as they are processed and become available.
let mut default_ban_rib = Rib::new(ForwardTyParamBanRibKind);
let mut found_default = false;
default_ban_rib.bindings.extend(generics.params.iter()
.filter_map(|param| match param.kind {
GenericParamKind::Const { .. } |
GenericParamKind::Lifetime { .. } => None,
GenericParamKind::Type { ref default, .. } => {
found_default |= default.is_some();
if found_default {
Some((Ident::with_dummy_span(param.ident.name), Res::Err))
} else {
None
}
}
}));
// We also ban access to type parameters for use as the types of const parameters.
let mut const_ty_param_ban_rib = Rib::new(TyParamAsConstParamTy);
const_ty_param_ban_rib.bindings.extend(generics.params.iter()
.filter(|param| {
if let GenericParamKind::Type { .. } = param.kind {
true
} else {
false
}
})
.map(|param| (Ident::with_dummy_span(param.ident.name), Res::Err)));
for param in &generics.params {
match param.kind {
GenericParamKind::Lifetime { .. } => self.visit_generic_param(param),
GenericParamKind::Type { ref default, .. } => {
for bound in &param.bounds {
self.visit_param_bound(bound);
}
if let Some(ref ty) = default {
self.ribs[TypeNS].push(default_ban_rib);
self.visit_ty(ty);
default_ban_rib = self.ribs[TypeNS].pop().unwrap();
}
// Allow all following defaults to refer to this type parameter.
default_ban_rib.bindings.remove(&Ident::with_dummy_span(param.ident.name));
}
GenericParamKind::Const { ref ty } => {
self.ribs[TypeNS].push(const_ty_param_ban_rib);
for bound in &param.bounds {
self.visit_param_bound(bound);
}
self.visit_ty(ty);
const_ty_param_ban_rib = self.ribs[TypeNS].pop().unwrap();
}
}
}
for p in &generics.where_clause.predicates {
self.visit_where_predicate(p);
}
}
}
impl<'a, 'b> LateResolutionVisitor<'a, '_> {
fn new(resolver: &'b mut Resolver<'a>) -> LateResolutionVisitor<'a, 'b> {
// During late resolution we only track the module component of the parent scope,
// although it may be useful to track other components as well for diagnostics.
let graph_root = resolver.graph_root;
let parent_scope = ParentScope::module(graph_root);
let start_rib_kind = ModuleRibKind(graph_root);
LateResolutionVisitor {
r: resolver,
parent_scope,
ribs: PerNS {
value_ns: vec![Rib::new(start_rib_kind)],
type_ns: vec![Rib::new(start_rib_kind)],
macro_ns: vec![Rib::new(start_rib_kind)],
},
label_ribs: Vec::new(),
current_trait_ref: None,
current_trait_assoc_types: Vec::new(),
current_self_type: None,
current_self_item: None,
unused_labels: Default::default(),
current_type_ascription: Vec::new(),
}
}
fn resolve_ident_in_lexical_scope(&mut self,
ident: Ident,
ns: Namespace,
record_used_id: Option<NodeId>,
path_span: Span)
-> Option<LexicalScopeBinding<'a>> {
self.r.resolve_ident_in_lexical_scope(
ident, ns, &self.parent_scope, record_used_id, path_span, &self.ribs[ns]
)
}
fn resolve_path(
&mut self,
path: &[Segment],
opt_ns: Option<Namespace>, // `None` indicates a module path in import
record_used: bool,
path_span: Span,
crate_lint: CrateLint,
) -> PathResult<'a> {
self.r.resolve_path_with_ribs(
path, opt_ns, &self.parent_scope, record_used, path_span, crate_lint, Some(&self.ribs)
)
}
// AST resolution
//
// We maintain a list of value ribs and type ribs.
//
// Simultaneously, we keep track of the current position in the module
// graph in the `parent_scope.module` pointer. When we go to resolve a name in
// the value or type namespaces, we first look through all the ribs and
// then query the module graph. When we resolve a name in the module
// namespace, we can skip all the ribs (since nested modules are not
// allowed within blocks in Rust) and jump straight to the current module
// graph node.
//
// Named implementations are handled separately. When we find a method
// call, we consult the module node to find all of the implementations in
// scope. This information is lazily cached in the module node. We then
// generate a fake "implementation scope" containing all the
// implementations thus found, for compatibility with old resolve pass.
/// Do some `work` within a new innermost rib of the given `kind` in the given namespace (`ns`).
fn with_rib<T>(
&mut self,
ns: Namespace,
kind: RibKind<'a>,
work: impl FnOnce(&mut Self) -> T,
) -> T {
self.ribs[ns].push(Rib::new(kind));
let ret = work(self);
self.ribs[ns].pop();
ret
}
fn with_scope<T>(&mut self, id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
let id = self.r.definitions.local_def_id(id);
let module = self.r.module_map.get(&id).cloned(); // clones a reference
if let Some(module) = module {
// Move down in the graph.
let orig_module = replace(&mut self.parent_scope.module, module);
self.with_rib(ValueNS, ModuleRibKind(module), |this| {
this.with_rib(TypeNS, ModuleRibKind(module), |this| {
let ret = f(this);
this.parent_scope.module = orig_module;
ret
})
})
} else {
f(self)
}
}
/// Searches the current set of local scopes for labels. Returns the first non-`None` label that
/// is returned by the given predicate function
///
/// Stops after meeting a closure.
fn search_label<P, R>(&self, mut ident: Ident, pred: P) -> Option<R>
where P: Fn(&Rib<'_, NodeId>, Ident) -> Option<R>
{
for rib in self.label_ribs.iter().rev() {
match rib.kind {
NormalRibKind => {}
// If an invocation of this macro created `ident`, give up on `ident`
// and switch to `ident`'s source from the macro definition.
MacroDefinition(def) => {
if def == self.r.macro_def(ident.span.ctxt()) {
ident.span.remove_mark();
}
}
_ => {
// Do not resolve labels across function boundary
return None;
}
}
let r = pred(rib, ident);
if r.is_some() {
return r;
}
}
None
}
fn resolve_adt(&mut self, item: &Item, generics: &Generics) {
debug!("resolve_adt");
self.with_current_self_item(item, |this| {
this.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| {
let item_def_id = this.r.definitions.local_def_id(item.id);
this.with_self_rib(Res::SelfTy(None, Some(item_def_id)), |this| {
visit::walk_item(this, item);
});
});
});
}
fn future_proof_import(&mut self, use_tree: &UseTree) {
let segments = &use_tree.prefix.segments;
if !segments.is_empty() {
let ident = segments[0].ident;
if ident.is_path_segment_keyword() || ident.span.rust_2015() {
return;
}
let nss = match use_tree.kind {
UseTreeKind::Simple(..) if segments.len() == 1 => &[TypeNS, ValueNS][..],
_ => &[TypeNS],
};
let report_error = |this: &Self, ns| {
let what = if ns == TypeNS { "type parameters" } else { "local variables" };
this.r.session.span_err(ident.span, &format!("imports cannot refer to {}", what));
};
for &ns in nss {
match self.resolve_ident_in_lexical_scope(ident, ns, None, use_tree.prefix.span) {
Some(LexicalScopeBinding::Res(..)) => {
report_error(self, ns);
}
Some(LexicalScopeBinding::Item(binding)) => {
let orig_blacklisted_binding =
replace(&mut self.r.blacklisted_binding, Some(binding));
if let Some(LexicalScopeBinding::Res(..)) =
self.resolve_ident_in_lexical_scope(ident, ns, None,
use_tree.prefix.span) {
report_error(self, ns);
}
self.r.blacklisted_binding = orig_blacklisted_binding;
}
None => {}
}
}
} else if let UseTreeKind::Nested(use_trees) = &use_tree.kind {
for (use_tree, _) in use_trees {
self.future_proof_import(use_tree);
}
}
}
fn resolve_item(&mut self, item: &Item) {
let name = item.ident.name;
debug!("(resolving item) resolving {} ({:?})", name, item.node);
match item.node {
ItemKind::TyAlias(_, ref generics) |
ItemKind::OpaqueTy(_, ref generics) |
ItemKind::Fn(_, _, ref generics, _) => {
self.with_generic_param_rib(
HasGenericParams(generics, ItemRibKind),
|this| visit::walk_item(this, item)
);
}
ItemKind::Enum(_, ref generics) |
ItemKind::Struct(_, ref generics) |
ItemKind::Union(_, ref generics) => {
self.resolve_adt(item, generics);
}
ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
self.resolve_implementation(generics,
opt_trait_ref,
&self_type,
item.id,
impl_items),
ItemKind::Trait(.., ref generics, ref bounds, ref trait_items) => {
// Create a new rib for the trait-wide type parameters.
self.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| {
let local_def_id = this.r.definitions.local_def_id(item.id);
this.with_self_rib(Res::SelfTy(Some(local_def_id), None), |this| {
this.visit_generics(generics);
walk_list!(this, visit_param_bound, bounds);
for trait_item in trait_items {
this.with_trait_items(trait_items, |this| {
let generic_params = HasGenericParams(
&trait_item.generics,
AssocItemRibKind,
);
this.with_generic_param_rib(generic_params, |this| {
match trait_item.node {
TraitItemKind::Const(ref ty, ref default) => {
this.visit_ty(ty);
// Only impose the restrictions of
// ConstRibKind for an actual constant
// expression in a provided default.
if let Some(ref expr) = *default{
this.with_constant_rib(|this| {
this.visit_expr(expr);
});
}
}
TraitItemKind::Method(_, _) => {
visit::walk_trait_item(this, trait_item)
}
TraitItemKind::Type(..) => {
visit::walk_trait_item(this, trait_item)
}
TraitItemKind::Macro(_) => {
panic!("unexpanded macro in resolve!")
}
};
});
});
}
});
});
}
ItemKind::TraitAlias(ref generics, ref bounds) => {
// Create a new rib for the trait-wide type parameters.
self.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| {
let local_def_id = this.r.definitions.local_def_id(item.id);
this.with_self_rib(Res::SelfTy(Some(local_def_id), None), |this| {
this.visit_generics(generics);
walk_list!(this, visit_param_bound, bounds);
});
});
}
ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
self.with_scope(item.id, |this| {
visit::walk_item(this, item);
});
}
ItemKind::Static(ref ty, _, ref expr) |
ItemKind::Const(ref ty, ref expr) => {
debug!("resolve_item ItemKind::Const");
self.with_item_rib(|this| {
this.visit_ty(ty);
this.with_constant_rib(|this| {
this.visit_expr(expr);
});
});
}
ItemKind::Use(ref use_tree) => {
self.future_proof_import(use_tree);
}
ItemKind::ExternCrate(..) |
ItemKind::MacroDef(..) | ItemKind::GlobalAsm(..) => {
// do nothing, these are just around to be encoded
}
ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
}
}
fn with_generic_param_rib<'c, F>(&'c mut self, generic_params: GenericParameters<'a, 'c>, f: F)
where F: FnOnce(&mut Self)
{
debug!("with_generic_param_rib");
match generic_params {
HasGenericParams(generics, rib_kind) => {
let mut function_type_rib = Rib::new(rib_kind);
let mut function_value_rib = Rib::new(rib_kind);
let mut seen_bindings = FxHashMap::default();
// We also can't shadow bindings from the parent item
if let AssocItemRibKind = rib_kind {
let mut add_bindings_for_ns = |ns| {
let parent_rib = self.ribs[ns].iter()
.rfind(|rib| if let ItemRibKind = rib.kind { true } else { false })
.expect("associated item outside of an item");
seen_bindings.extend(
parent_rib.bindings.iter().map(|(ident, _)| (*ident, ident.span)),
);
};
add_bindings_for_ns(ValueNS);
add_bindings_for_ns(TypeNS);
}
for param in &generics.params {
match param.kind {
GenericParamKind::Lifetime { .. } => {}
GenericParamKind::Type { .. } => {
let ident = param.ident.modern();
debug!("with_generic_param_rib: {}", param.id);
if seen_bindings.contains_key(&ident) {
let span = seen_bindings.get(&ident).unwrap();
let err = ResolutionError::NameAlreadyUsedInParameterList(
ident.name,
*span,
);
self.r.report_error(param.ident.span, err);
}
seen_bindings.entry(ident).or_insert(param.ident.span);
// Plain insert (no renaming).
let res = Res::Def(
DefKind::TyParam,
self.r.definitions.local_def_id(param.id),
);
function_type_rib.bindings.insert(ident, res);
self.r.record_partial_res(param.id, PartialRes::new(res));
}
GenericParamKind::Const { .. } => {
let ident = param.ident.modern();
debug!("with_generic_param_rib: {}", param.id);
if seen_bindings.contains_key(&ident) {
let span = seen_bindings.get(&ident).unwrap();
let err = ResolutionError::NameAlreadyUsedInParameterList(
ident.name,
*span,
);
self.r.report_error(param.ident.span, err);
}
seen_bindings.entry(ident).or_insert(param.ident.span);
let res = Res::Def(
DefKind::ConstParam,
self.r.definitions.local_def_id(param.id),
);
function_value_rib.bindings.insert(ident, res);
self.r.record_partial_res(param.id, PartialRes::new(res));
}
}
}
self.ribs[ValueNS].push(function_value_rib);
self.ribs[TypeNS].push(function_type_rib);
}
NoGenericParams => {
// Nothing to do.
}
}
f(self);
if let HasGenericParams(..) = generic_params {
self.ribs[TypeNS].pop();
self.ribs[ValueNS].pop();
}
}
fn with_label_rib(&mut self, kind: RibKind<'a>, f: impl FnOnce(&mut Self)) {
self.label_ribs.push(Rib::new(kind));
f(self);
self.label_ribs.pop();
}
fn with_item_rib(&mut self, f: impl FnOnce(&mut Self)) {
self.with_rib(ValueNS, ItemRibKind, |this| this.with_rib(TypeNS, ItemRibKind, f))
}
fn with_constant_rib(&mut self, f: impl FnOnce(&mut Self)) {
debug!("with_constant_rib");
self.with_rib(ValueNS, ConstantItemRibKind, |this| {
this.with_label_rib(ConstantItemRibKind, f);
});
}
fn with_current_self_type<T>(&mut self, self_type: &Ty, f: impl FnOnce(&mut Self) -> T) -> T {
// Handle nested impls (inside fn bodies)
let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
let result = f(self);
self.current_self_type = previous_value;
result
}
fn with_current_self_item<T>(&mut self, self_item: &Item, f: impl FnOnce(&mut Self) -> T) -> T {
let previous_value = replace(&mut self.current_self_item, Some(self_item.id));
let result = f(self);
self.current_self_item = previous_value;
result
}
/// When evaluating a `trait` use its associated types' idents for suggestionsa in E0412.
fn with_trait_items<T>(
&mut self,
trait_items: &Vec<TraitItem>,
f: impl FnOnce(&mut Self) -> T,
) -> T {
let trait_assoc_types = replace(
&mut self.current_trait_assoc_types,
trait_items.iter().filter_map(|item| match &item.node {
TraitItemKind::Type(bounds, _) if bounds.len() == 0 => Some(item.ident),
_ => None,
}).collect(),
);
let result = f(self);
self.current_trait_assoc_types = trait_assoc_types;
result
}
/// This is called to resolve a trait reference from an `impl` (i.e., `impl Trait for Foo`).
fn with_optional_trait_ref<T>(
&mut self,
opt_trait_ref: Option<&TraitRef>,
f: impl FnOnce(&mut Self, Option<DefId>) -> T
) -> T {
let mut new_val = None;
let mut new_id = None;
if let Some(trait_ref) = opt_trait_ref {
let path: Vec<_> = Segment::from_path(&trait_ref.path);
let res = self.smart_resolve_path_fragment(
trait_ref.ref_id,
None,
&path,
trait_ref.path.span,
PathSource::Trait(AliasPossibility::No),
CrateLint::SimplePath(trait_ref.ref_id),
).base_res();
if res != Res::Err {
new_id = Some(res.def_id());
let span = trait_ref.path.span;
if let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
self.resolve_path(
&path,
Some(TypeNS),
false,
span,
CrateLint::SimplePath(trait_ref.ref_id),
)
{
new_val = Some((module, trait_ref.clone()));
}
}
}
let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
let result = f(self, new_id);
self.current_trait_ref = original_trait_ref;
result
}
fn with_self_rib_ns(&mut self, ns: Namespace, self_res: Res, f: impl FnOnce(&mut Self)) {
let mut self_type_rib = Rib::new(NormalRibKind);
// Plain insert (no renaming, since types are not currently hygienic)
self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
self.ribs[ns].push(self_type_rib);
f(self);
self.ribs[ns].pop();
}
fn with_self_rib(&mut self, self_res: Res, f: impl FnOnce(&mut Self)) {
self.with_self_rib_ns(TypeNS, self_res, f)
}
fn resolve_implementation(&mut self,
generics: &Generics,
opt_trait_reference: &Option<TraitRef>,
self_type: &Ty,
item_id: NodeId,
impl_items: &[ImplItem]) {
debug!("resolve_implementation");
// If applicable, create a rib for the type parameters.
self.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| {
// Dummy self type for better errors if `Self` is used in the trait path.
this.with_self_rib(Res::SelfTy(None, None), |this| {
// Resolve the trait reference, if necessary.
this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
let item_def_id = this.r.definitions.local_def_id(item_id);
this.with_self_rib(Res::SelfTy(trait_id, Some(item_def_id)), |this| {
if let Some(trait_ref) = opt_trait_reference.as_ref() {
// Resolve type arguments in the trait path.
visit::walk_trait_ref(this, trait_ref);
}
// Resolve the self type.
this.visit_ty(self_type);
// Resolve the generic parameters.
this.visit_generics(generics);
// Resolve the items within the impl.
this.with_current_self_type(self_type, |this| {
this.with_self_rib_ns(ValueNS, Res::SelfCtor(item_def_id), |this| {
debug!("resolve_implementation with_self_rib_ns(ValueNS, ...)");
for impl_item in impl_items {
// We also need a new scope for the impl item type parameters.
let generic_params = HasGenericParams(&impl_item.generics,
AssocItemRibKind);
this.with_generic_param_rib(generic_params, |this| {
use crate::ResolutionError::*;
match impl_item.node {
ImplItemKind::Const(..) => {
debug!(
"resolve_implementation ImplItemKind::Const",
);
// If this is a trait impl, ensure the const
// exists in trait
this.check_trait_item(
impl_item.ident,
ValueNS,
impl_item.span,
|n, s| ConstNotMemberOfTrait(n, s),
);
this.with_constant_rib(|this| {
visit::walk_impl_item(this, impl_item)
});
}
ImplItemKind::Method(..) => {
// If this is a trait impl, ensure the method
// exists in trait
this.check_trait_item(impl_item.ident,
ValueNS,
impl_item.span,
|n, s| MethodNotMemberOfTrait(n, s));
visit::walk_impl_item(this, impl_item);
}
ImplItemKind::TyAlias(ref ty) => {
// If this is a trait impl, ensure the type
// exists in trait
this.check_trait_item(impl_item.ident,
TypeNS,
impl_item.span,
|n, s| TypeNotMemberOfTrait(n, s));
this.visit_ty(ty);
}
ImplItemKind::OpaqueTy(ref bounds) => {
// If this is a trait impl, ensure the type
// exists in trait
this.check_trait_item(impl_item.ident,
TypeNS,
impl_item.span,
|n, s| TypeNotMemberOfTrait(n, s));
for bound in bounds {
this.visit_param_bound(bound);
}
}
ImplItemKind::Macro(_) =>
panic!("unexpanded macro in resolve!"),
}
});
}
});
});
});
});
});
});
}
fn check_trait_item<F>(&mut self, ident: Ident, ns: Namespace, span: Span, err: F)
where F: FnOnce(Name, &str) -> ResolutionError<'_>
{
// If there is a TraitRef in scope for an impl, then the method must be in the
// trait.
if let Some((module, _)) = self.current_trait_ref {
if self.r.resolve_ident_in_module(
ModuleOrUniformRoot::Module(module),
ident,
ns,
&self.parent_scope,
false,
span,
).is_err() {
let path = &self.current_trait_ref.as_ref().unwrap().1.path;
self.r.report_error(span, err(ident.name, &path_names_to_string(path)));
}
}
}
fn resolve_params(&mut self, params: &[Param]) {
let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
for Param { pat, ty, .. } in params {
self.resolve_pattern(pat, PatternSource::FnParam, &mut bindings);
self.visit_ty(ty);
debug!("(resolving function / closure) recorded parameter");
}
}
fn resolve_local(&mut self, local: &Local) {
// Resolve the type.
walk_list!(self, visit_ty, &local.ty);
// Resolve the initializer.
walk_list!(self, visit_expr, &local.init);
// Resolve the pattern.
self.resolve_pattern_top(&local.pat, PatternSource::Let);
}
/// build a map from pattern identifiers to binding-info's.
/// this is done hygienically. This could arise for a macro
/// that expands into an or-pattern where one 'x' was from the
/// user and one 'x' came from the macro.
fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
let mut binding_map = FxHashMap::default();
pat.walk(&mut |pat| {
match pat.node {
PatKind::Ident(binding_mode, ident, ref sub_pat)
if sub_pat.is_some() || self.is_base_res_local(pat.id) =>
{
binding_map.insert(ident, BindingInfo { span: ident.span, binding_mode });
}
PatKind::Or(ref ps) => {
// Check the consistency of this or-pattern and
// then add all bindings to the larger map.
for bm in self.check_consistent_bindings(ps) {
binding_map.extend(bm);
}
return false;
}
_ => {}
}
true
});
binding_map
}
fn is_base_res_local(&self, nid: NodeId) -> bool {
match self.r.partial_res_map.get(&nid).map(|res| res.base_res()) {
Some(Res::Local(..)) => true,
_ => false,
}
}
/// Checks that all of the arms in an or-pattern have exactly the
/// same set of bindings, with the same binding modes for each.
fn check_consistent_bindings(&mut self, pats: &[P<Pat>]) -> Vec<BindingMap> {
let mut missing_vars = FxHashMap::default();
let mut inconsistent_vars = FxHashMap::default();
// 1) Compute the binding maps of all arms.
let maps = pats.iter()
.map(|pat| self.binding_mode_map(pat))
.collect::<Vec<_>>();
// 2) Record any missing bindings or binding mode inconsistencies.
for (map_outer, pat_outer) in pats.iter().enumerate().map(|(idx, pat)| (&maps[idx], pat)) {
// Check against all arms except for the same pattern which is always self-consistent.
let inners = pats.iter().enumerate()
.filter(|(_, pat)| pat.id != pat_outer.id)
.flat_map(|(idx, _)| maps[idx].iter())
.map(|(key, binding)| (key.name, map_outer.get(&key), binding));
for (name, info, &binding_inner) in inners {
match info {
None => { // The inner binding is missing in the outer.
let binding_error = missing_vars
.entry(name)
.or_insert_with(|| BindingError {
name,
origin: BTreeSet::new(),
target: BTreeSet::new(),
could_be_path: name.as_str().starts_with(char::is_uppercase),
});
binding_error.origin.insert(binding_inner.span);
binding_error.target.insert(pat_outer.span);
}
Some(binding_outer) => {
if binding_outer.binding_mode != binding_inner.binding_mode {
// The binding modes in the outer and inner bindings differ.
inconsistent_vars
.entry(name)
.or_insert((binding_inner.span, binding_outer.span));
}
}
}
}
}
// 3) Report all missing variables we found.
let mut missing_vars = missing_vars.iter_mut().collect::<Vec<_>>();
missing_vars.sort();
for (name, mut v) in missing_vars {
if inconsistent_vars.contains_key(name) {
v.could_be_path = false;
}
self.r.report_error(
*v.origin.iter().next().unwrap(),
ResolutionError::VariableNotBoundInPattern(v));
}
// 4) Report all inconsistencies in binding modes we found.
let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
inconsistent_vars.sort();
for (name, v) in inconsistent_vars {
self.r.report_error(v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
}
// 5) Finally bubble up all the binding maps.
maps
}
/// Check the consistency of the outermost or-patterns.
fn check_consistent_bindings_top(&mut self, pat: &Pat) {
pat.walk(&mut |pat| match pat.node {
PatKind::Or(ref ps) => {
self.check_consistent_bindings(ps);
false
},
_ => true,
})
}
fn resolve_arm(&mut self, arm: &Arm) {
self.with_rib(ValueNS, NormalRibKind, |this| {
this.resolve_pattern_top(&arm.pat, PatternSource::Match);
walk_list!(this, visit_expr, &arm.guard);
this.visit_expr(&arm.body);
});
}
/// Arising from `source`, resolve a top level pattern.
fn resolve_pattern_top(&mut self, pat: &Pat, pat_src: PatternSource) {
let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
self.resolve_pattern(pat, pat_src, &mut bindings);
}
fn resolve_pattern(
&mut self,
pat: &Pat,
pat_src: PatternSource,
bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
) {
self.resolve_pattern_inner(pat, pat_src, bindings);
// This has to happen *after* we determine which pat_idents are variants:
self.check_consistent_bindings_top(pat);
visit::walk_pat(self, pat);
}
/// Resolve bindings in a pattern. This is a helper to `resolve_pattern`.
///
/// ### `bindings`
///
/// A stack of sets of bindings accumulated.
///
/// In each set, `PatBoundCtx::Product` denotes that a found binding in it should
/// be interpreted as re-binding an already bound binding. This results in an error.
/// Meanwhile, `PatBound::Or` denotes that a found binding in the set should result
/// in reusing this binding rather than creating a fresh one.
///
/// When called at the top level, the stack must have a single element
/// with `PatBound::Product`. Otherwise, pushing to the stack happens as
/// or-patterns (`p_0 | ... | p_n`) are encountered and the context needs
/// to be switched to `PatBoundCtx::Or` and then `PatBoundCtx::Product` for each `p_i`.
/// When each `p_i` has been dealt with, the top set is merged with its parent.
/// When a whole or-pattern has been dealt with, the thing happens.
///
/// See the implementation and `fresh_binding` for more details.
fn resolve_pattern_inner(
&mut self,
pat: &Pat,
pat_src: PatternSource,
bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
) {
// Visit all direct subpatterns of this pattern.
pat.walk(&mut |pat| {
debug!("resolve_pattern pat={:?} node={:?}", pat, pat.node);
match pat.node {
PatKind::Ident(bmode, ident, ref sub) => {
// First try to resolve the identifier as some existing entity,
// then fall back to a fresh binding.
let has_sub = sub.is_some();
let res = self.try_resolve_as_non_binding(pat_src, pat, bmode, ident, has_sub)
.unwrap_or_else(|| self.fresh_binding(ident, pat.id, pat_src, bindings));
self.r.record_partial_res(pat.id, PartialRes::new(res));
}
PatKind::TupleStruct(ref path, ..) => {
self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
}
PatKind::Path(ref qself, ref path) => {
self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
}
PatKind::Struct(ref path, ..) => {
self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
}
PatKind::Or(ref ps) => {
// Add a new set of bindings to the stack. `Or` here records that when a
// binding already exists in this set, it should not result in an error because
// `V1(a) | V2(a)` must be allowed and are checked for consistency later.
bindings.push((PatBoundCtx::Or, Default::default()));
for p in ps {
// Now we need to switch back to a product context so that each
// part of the or-pattern internally rejects already bound names.
// For example, `V1(a) | V2(a, a)` and `V1(a, a) | V2(a)` are bad.
bindings.push((PatBoundCtx::Product, Default::default()));
self.resolve_pattern_inner(p, pat_src, bindings);
// Move up the non-overlapping bindings to the or-pattern.
// Existing bindings just get "merged".
let collected = bindings.pop().unwrap().1;
bindings.last_mut().unwrap().1.extend(collected);
}
// This or-pattern itself can itself be part of a product,
// e.g. `(V1(a) | V2(a), a)` or `(a, V1(a) | V2(a))`.
// Both cases bind `a` again in a product pattern and must be rejected.
let collected = bindings.pop().unwrap().1;
bindings.last_mut().unwrap().1.extend(collected);
// Prevent visiting `ps` as we've already done so above.
return false;
}
_ => {}
}
true
});
}
fn fresh_binding(
&mut self,
ident: Ident,
pat_id: NodeId,
pat_src: PatternSource,
bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
) -> Res {
// Add the binding to the local ribs, if it doesn't already exist in the bindings map.
// (We must not add it if it's in the bindings map because that breaks the assumptions
// later passes make about or-patterns.)
let ident = ident.modern_and_legacy();
// Walk outwards the stack of products / or-patterns and
// find out if the identifier has been bound in any of these.
let mut already_bound_and = false;
let mut already_bound_or = false;
for (is_sum, set) in bindings.iter_mut().rev() {
match (is_sum, set.get(&ident).cloned()) {
// Already bound in a product pattern, e.g. `(a, a)` which is not allowed.
(PatBoundCtx::Product, Some(..)) => already_bound_and = true,
// Already bound in an or-pattern, e.g. `V1(a) | V2(a)`.
// This is *required* for consistency which is checked later.
(PatBoundCtx::Or, Some(..)) => already_bound_or = true,
// Not already bound here.
_ => {}
}
}
if already_bound_and {
// Overlap in a product pattern somewhere; report an error.
use ResolutionError::*;
let error = match pat_src {
// `fn f(a: u8, a: u8)`:
PatternSource::FnParam => IdentifierBoundMoreThanOnceInParameterList,
// `Variant(a, a)`:
_ => IdentifierBoundMoreThanOnceInSamePattern,
};
self.r.report_error(ident.span, error(&ident.as_str()));
}
// Record as bound if it's valid:
let ident_valid = ident.name != kw::Invalid;
if ident_valid {
bindings.last_mut().unwrap().1.insert(ident);
}
if already_bound_or {
// `Variant1(a) | Variant2(a)`, ok
// Reuse definition from the first `a`.
self.innermost_rib_bindings(ValueNS)[&ident]
} else {
let res = Res::Local(pat_id);
if ident_valid {
// A completely fresh binding add to the set if it's valid.
self.innermost_rib_bindings(ValueNS).insert(ident, res);
}
res
}
}
fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut IdentMap<Res> {
&mut self.ribs[ns].last_mut().unwrap().bindings
}
fn try_resolve_as_non_binding(
&mut self,
pat_src: PatternSource,
pat: &Pat,
bm: BindingMode,
ident: Ident,
has_sub: bool,
) -> Option<Res> {
let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, pat.span)?.item()?;
let res = binding.res();
// An immutable (no `mut`) by-value (no `ref`) binding pattern without
// a sub pattern (no `@ $pat`) is syntactically ambiguous as it could
// also be interpreted as a path to e.g. a constant, variant, etc.
let is_syntactic_ambiguity = !has_sub && bm == BindingMode::ByValue(Mutability::Immutable);
match res {
Res::Def(DefKind::Ctor(_, CtorKind::Const), _) |
Res::Def(DefKind::Const, _) if is_syntactic_ambiguity => {
// Disambiguate in favor of a unit struct/variant or constant pattern.
self.r.record_use(ident, ValueNS, binding, false);
Some(res)
}
Res::Def(DefKind::Ctor(..), _)
| Res::Def(DefKind::Const, _)
| Res::Def(DefKind::Static, _) => {
// This is unambiguously a fresh binding, either syntactically
// (e.g., `IDENT @ PAT` or `ref IDENT`) or because `IDENT` resolves
// to something unusable as a pattern (e.g., constructor function),
// but we still conservatively report an error, see
// issues/33118#issuecomment-233962221 for one reason why.
self.r.report_error(
ident.span,
ResolutionError::BindingShadowsSomethingUnacceptable(
pat_src.descr(),
ident.name,
binding,
),
);
None
}
Res::Def(DefKind::Fn, _) | Res::Err => {
// These entities are explicitly allowed to be shadowed by fresh bindings.
None
}
res => {
span_bug!(ident.span, "unexpected resolution for an \
identifier in pattern: {:?}", res);
}
}
}
// High-level and context dependent path resolution routine.
// Resolves the path and records the resolution into definition map.
// If resolution fails tries several techniques to find likely
// resolution candidates, suggest imports or other help, and report
// errors in user friendly way.
fn smart_resolve_path(&mut self,
id: NodeId,
qself: Option<&QSelf>,
path: &Path,
source: PathSource<'_>) {
self.smart_resolve_path_fragment(
id,
qself,
&Segment::from_path(path),
path.span,
source,
CrateLint::SimplePath(id),
);
}
fn smart_resolve_path_fragment(&mut self,
id: NodeId,
qself: Option<&QSelf>,
path: &[Segment],
span: Span,
source: PathSource<'_>,
crate_lint: CrateLint)
-> PartialRes {
let ns = source.namespace();
let is_expected = &|res| source.is_expected(res);
let report_errors = |this: &mut Self, res: Option<Res>| {
let (err, candidates) = this.smart_resolve_report_errors(path, span, source, res);
let def_id = this.parent_scope.module.normal_ancestor_id;
let node_id = this.r.definitions.as_local_node_id(def_id).unwrap();
let better = res.is_some();
this.r.use_injections.push(UseError { err, candidates, node_id, better });
PartialRes::new(Res::Err)
};
let partial_res = match self.resolve_qpath_anywhere(
id,
qself,
path,
ns,
span,
source.defer_to_typeck(),
crate_lint,
) {
Some(partial_res) if partial_res.unresolved_segments() == 0 => {
if is_expected(partial_res.base_res()) || partial_res.base_res() == Res::Err {
partial_res
} else {
// Add a temporary hack to smooth the transition to new struct ctor
// visibility rules. See #38932 for more details.
let mut res = None;
if let Res::Def(DefKind::Struct, def_id) = partial_res.base_res() {
if let Some((ctor_res, ctor_vis))
= self.r.struct_constructors.get(&def_id).cloned() {
if is_expected(ctor_res) &&
self.r.is_accessible_from(ctor_vis, self.parent_scope.module) {
let lint = lint::builtin::LEGACY_CONSTRUCTOR_VISIBILITY;
self.r.session.buffer_lint(lint, id, span,
"private struct constructors are not usable through \
re-exports in outer modules",
);
res = Some(PartialRes::new(ctor_res));
}
}
}
res.unwrap_or_else(|| report_errors(self, Some(partial_res.base_res())))
}
}
Some(partial_res) if source.defer_to_typeck() => {
// Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
// or `<T>::A::B`. If `B` should be resolved in value namespace then
// it needs to be added to the trait map.
if ns == ValueNS {
let item_name = path.last().unwrap().ident;
let traits = self.get_traits_containing_item(item_name, ns);
self.r.trait_map.insert(id, traits);
}
let mut std_path = vec![Segment::from_ident(Ident::with_dummy_span(sym::std))];
std_path.extend(path);
if self.r.primitive_type_table.primitive_types.contains_key(&path[0].ident.name) {
let cl = CrateLint::No;
let ns = Some(ns);
if let PathResult::Module(_) | PathResult::NonModule(_) =
self.resolve_path(&std_path, ns, false, span, cl) {
// check if we wrote `str::from_utf8` instead of `std::str::from_utf8`
let item_span = path.iter().last().map(|segment| segment.ident.span)
.unwrap_or(span);
debug!("accessed item from `std` submodule as a bare type {:?}", std_path);
let mut hm = self.r.session.confused_type_with_std_module.borrow_mut();
hm.insert(item_span, span);
// In some places (E0223) we only have access to the full path
hm.insert(span, span);
}
}
partial_res
}
_ => report_errors(self, None)
};
if let PathSource::TraitItem(..) = source {} else {
// Avoid recording definition of `A::B` in `<T as A>::B::C`.
self.r.record_partial_res(id, partial_res);
}
partial_res
}
fn self_type_is_available(&mut self, span: Span) -> bool {
let binding = self.resolve_ident_in_lexical_scope(
Ident::with_dummy_span(kw::SelfUpper),
TypeNS,
None,
span,
);
if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
}
fn self_value_is_available(&mut self, self_span: Span, path_span: Span) -> bool {
let ident = Ident::new(kw::SelfLower, self_span);
let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, path_span);
if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
}
// Resolve in alternative namespaces if resolution in the primary namespace fails.
fn resolve_qpath_anywhere(
&mut self,
id: NodeId,
qself: Option<&QSelf>,
path: &[Segment],
primary_ns: Namespace,
span: Span,
defer_to_typeck: bool,
crate_lint: CrateLint,
) -> Option<PartialRes> {
let mut fin_res = None;
for (i, ns) in [primary_ns, TypeNS, ValueNS].iter().cloned().enumerate() {
if i == 0 || ns != primary_ns {
match self.resolve_qpath(id, qself, path, ns, span, crate_lint) {
// If defer_to_typeck, then resolution > no resolution,
// otherwise full resolution > partial resolution > no resolution.
Some(partial_res) if partial_res.unresolved_segments() == 0 ||
defer_to_typeck =>
return Some(partial_res),
partial_res => if fin_res.is_none() { fin_res = partial_res },
}
}
}
// `MacroNS`
assert!(primary_ns != MacroNS);
if qself.is_none() {
let path_seg = |seg: &Segment| PathSegment::from_ident(seg.ident);
let path = Path { segments: path.iter().map(path_seg).collect(), span };
if let Ok((_, res)) = self.r.resolve_macro_path(
&path, None, &self.parent_scope, false, false
) {
return Some(PartialRes::new(res));
}
}
fin_res
}
/// Handles paths that may refer to associated items.
fn resolve_qpath(
&mut self,
id: NodeId,
qself: Option<&QSelf>,
path: &[Segment],
ns: Namespace,
span: Span,
crate_lint: CrateLint,
) -> Option<PartialRes> {
debug!(
"resolve_qpath(id={:?}, qself={:?}, path={:?}, ns={:?}, span={:?})",
id,
qself,
path,
ns,
span,
);
if let Some(qself) = qself {
if qself.position == 0 {
// This is a case like `<T>::B`, where there is no
// trait to resolve. In that case, we leave the `B`
// segment to be resolved by type-check.
return Some(PartialRes::with_unresolved_segments(
Res::Def(DefKind::Mod, DefId::local(CRATE_DEF_INDEX)), path.len()
));
}
// Make sure `A::B` in `<T as A::B>::C` is a trait item.
//
// Currently, `path` names the full item (`A::B::C`, in
// our example). so we extract the prefix of that that is
// the trait (the slice upto and including
// `qself.position`). And then we recursively resolve that,
// but with `qself` set to `None`.
//
// However, setting `qself` to none (but not changing the
// span) loses the information about where this path
// *actually* appears, so for the purposes of the crate
// lint we pass along information that this is the trait
// name from a fully qualified path, and this also
// contains the full span (the `CrateLint::QPathTrait`).
let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
let partial_res = self.smart_resolve_path_fragment(
id,
None,
&path[..=qself.position],
span,
PathSource::TraitItem(ns),
CrateLint::QPathTrait {
qpath_id: id,
qpath_span: qself.path_span,
},
);
// The remaining segments (the `C` in our example) will
// have to be resolved by type-check, since that requires doing
// trait resolution.
return Some(PartialRes::with_unresolved_segments(
partial_res.base_res(),
partial_res.unresolved_segments() + path.len() - qself.position - 1,
));
}
let result = match self.resolve_path(&path, Some(ns), true, span, crate_lint) {
PathResult::NonModule(path_res) => path_res,
PathResult::Module(ModuleOrUniformRoot::Module(module)) if !module.is_normal() => {
PartialRes::new(module.res().unwrap())
}
// In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
// don't report an error right away, but try to fallback to a primitive type.
// So, we are still able to successfully resolve something like
//
// use std::u8; // bring module u8 in scope
// fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
// u8::max_value() // OK, resolves to associated function <u8>::max_value,
// // not to non-existent std::u8::max_value
// }
//
// Such behavior is required for backward compatibility.
// The same fallback is used when `a` resolves to nothing.
PathResult::Module(ModuleOrUniformRoot::Module(_)) |
PathResult::Failed { .. }
if (ns == TypeNS || path.len() > 1) &&
self.r.primitive_type_table.primitive_types
.contains_key(&path[0].ident.name) => {
let prim = self.r.primitive_type_table.primitive_types[&path[0].ident.name];
PartialRes::with_unresolved_segments(Res::PrimTy(prim), path.len() - 1)
}
PathResult::Module(ModuleOrUniformRoot::Module(module)) =>
PartialRes::new(module.res().unwrap()),
PathResult::Failed { is_error_from_last_segment: false, span, label, suggestion } => {
self.r.report_error(span, ResolutionError::FailedToResolve { label, suggestion });
PartialRes::new(Res::Err)
}
PathResult::Module(..) | PathResult::Failed { .. } => return None,
PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"),
};
if path.len() > 1 && result.base_res() != Res::Err &&
path[0].ident.name != kw::PathRoot &&
path[0].ident.name != kw::DollarCrate {
let unqualified_result = {
match self.resolve_path(
&[*path.last().unwrap()],
Some(ns),
false,
span,
CrateLint::No,
) {
PathResult::NonModule(path_res) => path_res.base_res(),
PathResult::Module(ModuleOrUniformRoot::Module(module)) =>
module.res().unwrap(),
_ => return Some(result),
}
};
if result.base_res() == unqualified_result {
let lint = lint::builtin::UNUSED_QUALIFICATIONS;
self.r.session.buffer_lint(lint, id, span, "unnecessary qualification")
}
}
Some(result)
}
fn with_resolved_label(&mut self, label: Option<Label>, id: NodeId, f: impl FnOnce(&mut Self)) {
if let Some(label) = label {
self.unused_labels.insert(id, label.ident.span);
self.with_label_rib(NormalRibKind, |this| {
let ident = label.ident.modern_and_legacy();
this.label_ribs.last_mut().unwrap().bindings.insert(ident, id);
f(this);
});
} else {
f(self);
}
}
fn resolve_labeled_block(&mut self, label: Option<Label>, id: NodeId, block: &Block) {
self.with_resolved_label(label, id, |this| this.visit_block(block));
}
fn resolve_block(&mut self, block: &Block) {
debug!("(resolving block) entering block");
// Move down in the graph, if there's an anonymous module rooted here.
let orig_module = self.parent_scope.module;
let anonymous_module = self.r.block_map.get(&block.id).cloned(); // clones a reference
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(ModuleRibKind(anonymous_module)));
self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
self.parent_scope.module = anonymous_module;
} else {
self.ribs[ValueNS].push(Rib::new(NormalRibKind));
}
// Descend into the block.
for stmt in &block.stmts {
if let StmtKind::Item(ref item) = stmt.node {
if let ItemKind::MacroDef(..) = item.node {
num_macro_definition_ribs += 1;
let res = self.r.definitions.local_def_id(item.id);
self.ribs[ValueNS].push(Rib::new(MacroDefinition(res)));
self.label_ribs.push(Rib::new(MacroDefinition(res)));
}
}
self.visit_stmt(stmt);
}
// Move back up.
self.parent_scope.module = orig_module;
for _ in 0 .. num_macro_definition_ribs {
self.ribs[ValueNS].pop();
self.label_ribs.pop();
}
self.ribs[ValueNS].pop();
if anonymous_module.is_some() {
self.ribs[TypeNS].pop();
}
debug!("(resolving block) leaving block");
}
fn resolve_expr(&mut self, expr: &Expr, parent: Option<&Expr>) {
// First, record candidate traits for this expression if it could
// result in the invocation of a method call.
self.record_candidate_traits_for_expr_if_necessary(expr);
// Next, resolve the node.
match expr.node {
ExprKind::Path(ref qself, ref path) => {
self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
visit::walk_expr(self, expr);
}
ExprKind::Struct(ref path, ..) => {
self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
visit::walk_expr(self, expr);
}
ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
let node_id = self.search_label(label.ident, |rib, ident| {
rib.bindings.get(&ident.modern_and_legacy()).cloned()
});
match node_id {
None => {
// Search again for close matches...
// Picks the first label that is "close enough", which is not necessarily
// the closest match
let close_match = self.search_label(label.ident, |rib, ident| {
let names = rib.bindings.iter().filter_map(|(id, _)| {
if id.span.ctxt() == label.ident.span.ctxt() {
Some(&id.name)
} else {
None
}
});
find_best_match_for_name(names, &*ident.as_str(), None)
});
self.r.record_partial_res(expr.id, PartialRes::new(Res::Err));
self.r.report_error(
label.ident.span,
ResolutionError::UndeclaredLabel(&label.ident.as_str(), close_match),
);
}
Some(node_id) => {
// Since this res is a label, it is never read.
self.r.label_res_map.insert(expr.id, node_id);
self.unused_labels.remove(&node_id);
}
}
// visit `break` argument if any
visit::walk_expr(self, expr);
}
ExprKind::Let(ref pat, ref scrutinee) => {
self.visit_expr(scrutinee);
self.resolve_pattern_top(pat, PatternSource::Let);
}
ExprKind::If(ref cond, ref then, ref opt_else) => {
self.with_rib(ValueNS, NormalRibKind, |this| {
this.visit_expr(cond);
this.visit_block(then);
});
opt_else.as_ref().map(|expr| self.visit_expr(expr));
}
ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
ExprKind::While(ref cond, ref block, label) => {
self.with_resolved_label(label, expr.id, |this| {
this.with_rib(ValueNS, NormalRibKind, |this| {
this.visit_expr(cond);
this.visit_block(block);
})
});
}
ExprKind::ForLoop(ref pat, ref iter_expr, ref block, label) => {
self.visit_expr(iter_expr);
self.with_rib(ValueNS, NormalRibKind, |this| {
this.resolve_pattern_top(pat, PatternSource::For);
this.resolve_labeled_block(label, expr.id, block);
});
}
ExprKind::Block(ref block, label) => self.resolve_labeled_block(label, block.id, block),
// Equivalent to `visit::walk_expr` + passing some context to children.
ExprKind::Field(ref subexpression, _) => {
self.resolve_expr(subexpression, Some(expr));
}
ExprKind::MethodCall(ref segment, ref arguments) => {
let mut arguments = arguments.iter();
self.resolve_expr(arguments.next().unwrap(), Some(expr));
for argument in arguments {
self.resolve_expr(argument, None);
}
self.visit_path_segment(expr.span, segment);
}
ExprKind::Call(ref callee, ref arguments) => {
self.resolve_expr(callee, Some(expr));
for argument in arguments {
self.resolve_expr(argument, None);
}
}
ExprKind::Type(ref type_expr, _) => {
self.current_type_ascription.push(type_expr.span);
visit::walk_expr(self, expr);
self.current_type_ascription.pop();
}
// `async |x| ...` gets desugared to `|x| future_from_generator(|| ...)`, so we need to
// resolve the arguments within the proper scopes so that usages of them inside the
// closure are detected as upvars rather than normal closure arg usages.
ExprKind::Closure(_, IsAsync::Async { .. }, _, ref fn_decl, ref body, _span) => {
self.with_rib(ValueNS, NormalRibKind, |this| {
// Resolve arguments:
this.resolve_params(&fn_decl.inputs);
// No need to resolve return type --
// the outer closure return type is `FunctionRetTy::Default`.
// Now resolve the inner closure
{
// No need to resolve arguments: the inner closure has none.
// Resolve the return type:
visit::walk_fn_ret_ty(this, &fn_decl.output);
// Resolve the body
this.visit_expr(body);
}
});
}
_ => {
visit::walk_expr(self, expr);
}
}
}
fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
match expr.node {
ExprKind::Field(_, ident) => {
// FIXME(#6890): Even though you can't treat a method like a
// field, we need to add any trait methods we find that match
// the field name so that we can do some nice error reporting
// later on in typeck.
let traits = self.get_traits_containing_item(ident, ValueNS);
self.r.trait_map.insert(expr.id, traits);
}
ExprKind::MethodCall(ref segment, ..) => {
debug!("(recording candidate traits for expr) recording traits for {}",
expr.id);
let traits = self.get_traits_containing_item(segment.ident, ValueNS);
self.r.trait_map.insert(expr.id, traits);
}
_ => {
// Nothing to do.
}
}
}
fn get_traits_containing_item(&mut self, mut ident: Ident, ns: Namespace)
-> Vec<TraitCandidate> {
debug!("(getting traits containing item) looking for '{}'", ident.name);
let mut found_traits = Vec::new();
// Look for the current trait.
if let Some((module, _)) = self.current_trait_ref {
if self.r.resolve_ident_in_module(
ModuleOrUniformRoot::Module(module),
ident,
ns,
&self.parent_scope,
false,
module.span,
).is_ok() {
let def_id = module.def_id().unwrap();
found_traits.push(TraitCandidate { def_id: def_id, import_ids: smallvec![] });
}
}
ident.span = ident.span.modern();
let mut search_module = self.parent_scope.module;
loop {
self.get_traits_in_module_containing_item(ident, ns, search_module, &mut found_traits);
search_module = unwrap_or!(
self.r.hygienic_lexical_parent(search_module, &mut ident.span), break
);
}
if let Some(prelude) = self.r.prelude {
if !search_module.no_implicit_prelude {
self.get_traits_in_module_containing_item(ident, ns, prelude, &mut found_traits);
}
}
found_traits
}
fn get_traits_in_module_containing_item(&mut self,
ident: Ident,
ns: Namespace,
module: Module<'a>,
found_traits: &mut Vec<TraitCandidate>) {
assert!(ns == TypeNS || ns == ValueNS);
let mut traits = module.traits.borrow_mut();
if traits.is_none() {
let mut collected_traits = Vec::new();
module.for_each_child(self.r, |_, name, ns, binding| {
if ns != TypeNS { return }
match binding.res() {
Res::Def(DefKind::Trait, _) |
Res::Def(DefKind::TraitAlias, _) => collected_traits.push((name, binding)),
_ => (),
}
});
*traits = Some(collected_traits.into_boxed_slice());
}
for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
// Traits have pseudo-modules that can be used to search for the given ident.
if let Some(module) = binding.module() {
let mut ident = ident;
if ident.span.glob_adjust(
module.expansion,
binding.span,
).is_none() {
continue
}
if self.r.resolve_ident_in_module_unadjusted(
ModuleOrUniformRoot::Module(module),
ident,
ns,
&self.parent_scope,
false,
module.span,
).is_ok() {
let import_ids = self.find_transitive_imports(&binding.kind, trait_name);
let trait_def_id = module.def_id().unwrap();
found_traits.push(TraitCandidate { def_id: trait_def_id, import_ids });
}
} else if let Res::Def(DefKind::TraitAlias, _) = binding.res() {
// For now, just treat all trait aliases as possible candidates, since we don't
// know if the ident is somewhere in the transitive bounds.
let import_ids = self.find_transitive_imports(&binding.kind, trait_name);
let trait_def_id = binding.res().def_id();
found_traits.push(TraitCandidate { def_id: trait_def_id, import_ids });
} else {
bug!("candidate is not trait or trait alias?")
}
}
}
fn find_transitive_imports(&mut self, mut kind: &NameBindingKind<'_>,
trait_name: Ident) -> SmallVec<[NodeId; 1]> {
let mut import_ids = smallvec![];
while let NameBindingKind::Import { directive, binding, .. } = kind {
self.r.maybe_unused_trait_imports.insert(directive.id);
self.r.add_to_glob_map(&directive, trait_name);
import_ids.push(directive.id);
kind = &binding.kind;
};
import_ids
}
}
impl<'a> Resolver<'a> {
pub(crate) fn late_resolve_crate(&mut self, krate: &Crate) {
let mut late_resolution_visitor = LateResolutionVisitor::new(self);
visit::walk_crate(&mut late_resolution_visitor, krate);
for (id, span) in late_resolution_visitor.unused_labels.iter() {
self.session.buffer_lint(lint::builtin::UNUSED_LABELS, *id, *span, "unused label");
}
}
}
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