bjoernager/rust
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rust/compiler/rustc_resolve/src/late/diagnostics.rs

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use crate::diagnostics::{ImportSuggestion, LabelSuggestion, TypoSuggestion};
use crate::late::{AliasPossibility, LateResolutionVisitor, RibKind};
use crate::late::{LifetimeBinderKind, LifetimeRes, LifetimeRibKind, LifetimeUseSet};
use crate::path_names_to_string;
use crate::{Module, ModuleKind, ModuleOrUniformRoot};
use crate::{PathResult, PathSource, Segment};
use rustc_ast::visit::{FnCtxt, FnKind, LifetimeCtxt};
use rustc_ast::{
self as ast, AssocItemKind, Expr, ExprKind, GenericParam, GenericParamKind, Item, ItemKind,
NodeId, Path, Ty, TyKind, DUMMY_NODE_ID,
};
use rustc_ast_pretty::pprust::path_segment_to_string;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{
pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
MultiSpan,
};
use rustc_hir as hir;
use rustc_hir::def::Namespace::{self, *};
use rustc_hir::def::{self, CtorKind, CtorOf, DefKind};
use rustc_hir::def_id::{DefId, CRATE_DEF_ID, LOCAL_CRATE};
use rustc_hir::PrimTy;
use rustc_session::lint;
use rustc_session::parse::feature_err;
use rustc_session::Session;
use rustc_span::edition::Edition;
use rustc_span::hygiene::MacroKind;
use rustc_span::lev_distance::find_best_match_for_name;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{BytePos, Span};
use std::iter;
use std::ops::Deref;
type Res = def::Res<ast::NodeId>;
/// A field or associated item from self type suggested in case of resolution failure.
enum AssocSuggestion {
Field,
MethodWithSelf,
AssocFn,
AssocType,
AssocConst,
}
impl AssocSuggestion {
fn action(&self) -> &'static str {
match self {
AssocSuggestion::Field => "use the available field",
AssocSuggestion::MethodWithSelf => "call the method with the fully-qualified path",
AssocSuggestion::AssocFn => "call the associated function",
AssocSuggestion::AssocConst => "use the associated `const`",
AssocSuggestion::AssocType => "use the associated type",
}
}
}
fn is_self_type(path: &[Segment], namespace: Namespace) -> bool {
namespace == TypeNS && path.len() == 1 && path[0].ident.name == kw::SelfUpper
}
fn is_self_value(path: &[Segment], namespace: Namespace) -> bool {
namespace == ValueNS && path.len() == 1 && path[0].ident.name == kw::SelfLower
}
/// Gets the stringified path for an enum from an `ImportSuggestion` for an enum variant.
fn import_candidate_to_enum_paths(suggestion: &ImportSuggestion) -> (String, String) {
let variant_path = &suggestion.path;
let variant_path_string = path_names_to_string(variant_path);
let path_len = suggestion.path.segments.len();
let enum_path = ast::Path {
span: suggestion.path.span,
segments: suggestion.path.segments[0..path_len - 1].to_vec(),
tokens: None,
};
let enum_path_string = path_names_to_string(&enum_path);
(variant_path_string, enum_path_string)
}
/// Description of an elided lifetime.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
pub(super) struct MissingLifetime {
/// Used to overwrite the resolution with the suggestion, to avoid cascasing errors.
pub id: NodeId,
/// Where to suggest adding the lifetime.
pub span: Span,
/// How the lifetime was introduced, to have the correct space and comma.
pub kind: MissingLifetimeKind,
/// Number of elided lifetimes, used for elision in path.
pub count: usize,
}
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
pub(super) enum MissingLifetimeKind {
/// An explicit `'_`.
Underscore,
/// An elided lifetime `&' ty`.
Ampersand,
/// An elided lifetime in brackets with written brackets.
Comma,
/// An elided lifetime with elided brackets.
Brackets,
}
/// Description of the lifetimes appearing in a function parameter.
/// This is used to provide a literal explanation to the elision failure.
#[derive(Clone, Debug)]
pub(super) struct ElisionFnParameter {
/// The index of the argument in the original definition.
pub index: usize,
/// The name of the argument if it's a simple ident.
pub ident: Option<Ident>,
/// The number of lifetimes in the parameter.
pub lifetime_count: usize,
/// The span of the parameter.
pub span: Span,
}
/// Description of lifetimes that appear as candidates for elision.
/// This is used to suggest introducing an explicit lifetime.
#[derive(Debug)]
pub(super) enum LifetimeElisionCandidate {
/// This is not a real lifetime.
Ignore,
/// There is a named lifetime, we won't suggest anything.
Named,
Missing(MissingLifetime),
}
impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
fn def_span(&self, def_id: DefId) -> Option<Span> {
match def_id.krate {
LOCAL_CRATE => self.r.opt_span(def_id),
_ => Some(self.r.cstore().get_span_untracked(def_id, self.r.session)),
}
}
/// Handles error reporting for `smart_resolve_path_fragment` function.
/// Creates base error and amends it with one short label and possibly some longer helps/notes.
pub(crate) fn smart_resolve_report_errors(
&mut self,
path: &[Segment],
span: Span,
source: PathSource<'_>,
res: Option<Res>,
) -> (DiagnosticBuilder<'a, ErrorGuaranteed>, Vec<ImportSuggestion>) {
let ident_span = path.last().map_or(span, |ident| ident.ident.span);
let ns = source.namespace();
let is_expected = &|res| source.is_expected(res);
let is_enum_variant = &|res| matches!(res, Res::Def(DefKind::Variant, _));
debug!(?res, ?source);
// Make the base error.
struct BaseError<'a> {
msg: String,
fallback_label: String,
span: Span,
span_label: Option<(Span, &'a str)>,
could_be_expr: bool,
suggestion: Option<(Span, &'a str, String)>,
}
let mut expected = source.descr_expected();
let path_str = Segment::names_to_string(path);
let item_str = path.last().unwrap().ident;
let base_error = if let Some(res) = res {
BaseError {
msg: format!("expected {}, found {} `{}`", expected, res.descr(), path_str),
fallback_label: format!("not a {expected}"),
span,
span_label: match res {
Res::Def(kind, def_id) if kind == DefKind::TyParam => {
self.def_span(def_id).map(|span| (span, "found this type pararmeter"))
}
_ => None,
},
could_be_expr: match res {
Res::Def(DefKind::Fn, _) => {
// Verify whether this is a fn call or an Fn used as a type.
self.r
.session
.source_map()
.span_to_snippet(span)
.map(|snippet| snippet.ends_with(')'))
.unwrap_or(false)
}
Res::Def(
DefKind::Ctor(..) | DefKind::AssocFn | DefKind::Const | DefKind::AssocConst,
_,
)
| Res::SelfCtor(_)
| Res::PrimTy(_)
| Res::Local(_) => true,
_ => false,
},
suggestion: None,
}
} else {
let item_span = path.last().unwrap().ident.span;
let (mod_prefix, mod_str, suggestion) = if path.len() == 1 {
debug!(?self.diagnostic_metadata.current_impl_items);
debug!(?self.diagnostic_metadata.current_function);
let suggestion = if let Some(items) = self.diagnostic_metadata.current_impl_items
&& let Some((fn_kind, _)) = self.diagnostic_metadata.current_function
&& self.current_trait_ref.is_none()
&& let Some(FnCtxt::Assoc(_)) = fn_kind.ctxt()
&& let Some(item) = items.iter().find(|i| {
if let AssocItemKind::Fn(fn_) = &i.kind
&& !fn_.sig.decl.has_self()
&& i.ident.name == item_str.name
{
debug!(?item_str.name);
debug!(?fn_.sig.decl.inputs);
return true
}
false
})
{
Some((
item_span,
"consider using the associated function",
format!("Self::{}", item.ident)
))
} else {
None
};
(String::new(), "this scope".to_string(), suggestion)
} else if path.len() == 2 && path[0].ident.name == kw::PathRoot {
if self.r.session.edition() > Edition::Edition2015 {
// In edition 2018 onwards, the `::foo` syntax may only pull from the extern prelude
// which overrides all other expectations of item type
expected = "crate";
(String::new(), "the list of imported crates".to_string(), None)
} else {
(String::new(), "the crate root".to_string(), None)
}
} else if path.len() == 2 && path[0].ident.name == kw::Crate {
(String::new(), "the crate root".to_string(), None)
} else {
let mod_path = &path[..path.len() - 1];
let mod_prefix = match self.resolve_path(mod_path, Some(TypeNS), None) {
PathResult::Module(ModuleOrUniformRoot::Module(module)) => module.res(),
_ => None,
}
.map_or_else(String::new, |res| format!("{} ", res.descr()));
(mod_prefix, format!("`{}`", Segment::names_to_string(mod_path)), None)
};
let (fallback_label, suggestion) = if path_str == "async"
&& expected.starts_with("struct")
{
("`async` blocks are only allowed in Rust 2018 or later".to_string(), suggestion)
} else {
// check if we are in situation of typo like `True` instead of `true`.
let override_suggestion =
if ["true", "false"].contains(&item_str.to_string().to_lowercase().as_str()) {
let item_typo = item_str.to_string().to_lowercase();
Some((
item_span,
"you may want to use a bool value instead",
format!("{}", item_typo),
))
} else {
suggestion
};
(format!("not found in {mod_str}"), override_suggestion)
};
BaseError {
msg: format!("cannot find {expected} `{item_str}` in {mod_prefix}{mod_str}"),
fallback_label,
span: item_span,
span_label: None,
could_be_expr: false,
suggestion,
}
};
let code = source.error_code(res.is_some());
let mut err =
self.r.session.struct_span_err_with_code(base_error.span, &base_error.msg, code);
self.suggest_swapping_misplaced_self_ty_and_trait(&mut err, source, res, base_error.span);
if let Some((span, label)) = base_error.span_label {
err.span_label(span, label);
}
if let Some(sugg) = base_error.suggestion {
err.span_suggestion_verbose(sugg.0, sugg.1, sugg.2, Applicability::MaybeIncorrect);
}
if let Some(span) = self.diagnostic_metadata.current_block_could_be_bare_struct_literal {
err.multipart_suggestion(
"you might have meant to write a `struct` literal",
vec![
(span.shrink_to_lo(), "{ SomeStruct ".to_string()),
(span.shrink_to_hi(), "}".to_string()),
],
Applicability::HasPlaceholders,
);
}
match (source, self.diagnostic_metadata.in_if_condition) {
(
PathSource::Expr(_),
Some(Expr { span: expr_span, kind: ExprKind::Assign(lhs, _, _), .. }),
) => {
// Icky heuristic so we don't suggest:
// `if (i + 2) = 2` => `if let (i + 2) = 2` (approximately pattern)
// `if 2 = i` => `if let 2 = i` (lhs needs to contain error span)
if lhs.is_approximately_pattern() && lhs.span.contains(span) {
err.span_suggestion_verbose(
expr_span.shrink_to_lo(),
"you might have meant to use pattern matching",
"let ",
Applicability::MaybeIncorrect,
);
}
}
_ => {}
}
let is_assoc_fn = self.self_type_is_available();
// Emit help message for fake-self from other languages (e.g., `this` in Javascript).
if ["this", "my"].contains(&item_str.as_str()) && is_assoc_fn {
err.span_suggestion_short(
span,
"you might have meant to use `self` here instead",
"self",
Applicability::MaybeIncorrect,
);
if !self.self_value_is_available(path[0].ident.span) {
if let Some((FnKind::Fn(_, _, sig, ..), fn_span)) =
&self.diagnostic_metadata.current_function
{
let (span, sugg) = if let Some(param) = sig.decl.inputs.get(0) {
(param.span.shrink_to_lo(), "&self, ")
} else {
(
self.r
.session
.source_map()
.span_through_char(*fn_span, '(')
.shrink_to_hi(),
"&self",
)
};
err.span_suggestion_verbose(
span,
"if you meant to use `self`, you are also missing a `self` receiver \
argument",
sugg,
Applicability::MaybeIncorrect,
);
}
}
}
self.detect_assoct_type_constraint_meant_as_path(base_error.span, &mut err);
// Emit special messages for unresolved `Self` and `self`.
if is_self_type(path, ns) {
err.code(rustc_errors::error_code!(E0411));
err.span_label(
span,
"`Self` is only available in impls, traits, and type definitions".to_string(),
);
if let Some(item_kind) = self.diagnostic_metadata.current_item {
err.span_label(
item_kind.ident.span,
format!(
"`Self` not allowed in {} {}",
item_kind.kind.article(),
item_kind.kind.descr()
),
);
}
return (err, Vec::new());
}
if is_self_value(path, ns) {
debug!("smart_resolve_path_fragment: E0424, source={:?}", source);
err.code(rustc_errors::error_code!(E0424));
err.span_label(span, match source {
PathSource::Pat => "`self` value is a keyword and may not be bound to variables or shadowed",
_ => "`self` value is a keyword only available in methods with a `self` parameter",
});
if let Some((fn_kind, span)) = &self.diagnostic_metadata.current_function {
// The current function has a `self' parameter, but we were unable to resolve
// a reference to `self`. This can only happen if the `self` identifier we
// are resolving came from a different hygiene context.
if fn_kind.decl().inputs.get(0).map_or(false, |p| p.is_self()) {
err.span_label(*span, "this function has a `self` parameter, but a macro invocation can only access identifiers it receives from parameters");
} else {
let doesnt = if is_assoc_fn {
let (span, sugg) = fn_kind
.decl()
.inputs
.get(0)
.map(|p| (p.span.shrink_to_lo(), "&self, "))
.unwrap_or_else(|| {
// Try to look for the "(" after the function name, if possible.
// This avoids placing the suggestion into the visibility specifier.
let span = fn_kind
.ident()
.map_or(*span, |ident| span.with_lo(ident.span.hi()));
(
self.r
.session
.source_map()
.span_through_char(span, '(')
.shrink_to_hi(),
"&self",
)
});
err.span_suggestion_verbose(
span,
"add a `self` receiver parameter to make the associated `fn` a method",
sugg,
Applicability::MaybeIncorrect,
);
"doesn't"
} else {
"can't"
};
if let Some(ident) = fn_kind.ident() {
err.span_label(
ident.span,
&format!("this function {} have a `self` parameter", doesnt),
);
}
}
} else if let Some(item_kind) = self.diagnostic_metadata.current_item {
err.span_label(
item_kind.ident.span,
format!(
"`self` not allowed in {} {}",
item_kind.kind.article(),
item_kind.kind.descr()
),
);
}
return (err, Vec::new());
}
// Try to lookup name in more relaxed fashion for better error reporting.
let ident = path.last().unwrap().ident;
let mut candidates = self
.r
.lookup_import_candidates(ident, ns, &self.parent_scope, is_expected)
.into_iter()
.filter(|ImportSuggestion { did, .. }| {
match (did, res.and_then(|res| res.opt_def_id())) {
(Some(suggestion_did), Some(actual_did)) => *suggestion_did != actual_did,
_ => true,
}
})
.collect::<Vec<_>>();
let crate_def_id = CRATE_DEF_ID.to_def_id();
// Try to filter out intrinsics candidates, as long as we have
// some other candidates to suggest.
let intrinsic_candidates: Vec<_> = candidates
.drain_filter(|sugg| {
let path = path_names_to_string(&sugg.path);
path.starts_with("core::intrinsics::") || path.starts_with("std::intrinsics::")
})
.collect();
if candidates.is_empty() {
// Put them back if we have no more candidates to suggest...
candidates.extend(intrinsic_candidates);
}
if candidates.is_empty() && is_expected(Res::Def(DefKind::Enum, crate_def_id)) {
let mut enum_candidates: Vec<_> = self
.r
.lookup_import_candidates(ident, ns, &self.parent_scope, is_enum_variant)
.into_iter()
.map(|suggestion| import_candidate_to_enum_paths(&suggestion))
.filter(|(_, enum_ty_path)| !enum_ty_path.starts_with("std::prelude::"))
.collect();
if !enum_candidates.is_empty() {
if let (PathSource::Type, Some(span)) =
(source, self.diagnostic_metadata.current_type_ascription.last())
{
if self
.r
.session
.parse_sess
.type_ascription_path_suggestions
.borrow()
.contains(span)
{
// Already reported this issue on the lhs of the type ascription.
err.delay_as_bug();
return (err, candidates);
}
}
enum_candidates.sort();
// Contextualize for E0412 "cannot find type", but don't belabor the point
// (that it's a variant) for E0573 "expected type, found variant".
let preamble = if res.is_none() {
let others = match enum_candidates.len() {
1 => String::new(),
2 => " and 1 other".to_owned(),
n => format!(" and {} others", n),
};
format!("there is an enum variant `{}`{}; ", enum_candidates[0].0, others)
} else {
String::new()
};
let msg = format!("{}try using the variant's enum", preamble);
err.span_suggestions(
span,
&msg,
enum_candidates.into_iter().map(|(_variant_path, enum_ty_path)| enum_ty_path),
Applicability::MachineApplicable,
);
}
}
// Try Levenshtein algorithm.
let typo_sugg = self.lookup_typo_candidate(path, ns, is_expected);
if path.len() == 1 && self.self_type_is_available() {
if let Some(candidate) = self.lookup_assoc_candidate(ident, ns, is_expected) {
let self_is_available = self.self_value_is_available(path[0].ident.span);
match candidate {
AssocSuggestion::Field => {
if self_is_available {
err.span_suggestion(
span,
"you might have meant to use the available field",
format!("self.{path_str}"),
Applicability::MachineApplicable,
);
} else {
err.span_label(span, "a field by this name exists in `Self`");
}
}
AssocSuggestion::MethodWithSelf if self_is_available => {
err.span_suggestion(
span,
"you might have meant to call the method",
format!("self.{path_str}"),
Applicability::MachineApplicable,
);
}
AssocSuggestion::MethodWithSelf
| AssocSuggestion::AssocFn
| AssocSuggestion::AssocConst
| AssocSuggestion::AssocType => {
err.span_suggestion(
span,
&format!("you might have meant to {}", candidate.action()),
format!("Self::{path_str}"),
Applicability::MachineApplicable,
);
}
}
self.r.add_typo_suggestion(&mut err, typo_sugg, ident_span);
return (err, candidates);
}
// If the first argument in call is `self` suggest calling a method.
if let Some((call_span, args_span)) = self.call_has_self_arg(source) {
let mut args_snippet = String::new();
if let Some(args_span) = args_span {
if let Ok(snippet) = self.r.session.source_map().span_to_snippet(args_span) {
args_snippet = snippet;
}
}
err.span_suggestion(
call_span,
&format!("try calling `{ident}` as a method"),
format!("self.{path_str}({args_snippet})"),
Applicability::MachineApplicable,
);
return (err, candidates);
}
}
// Try context-dependent help if relaxed lookup didn't work.
if let Some(res) = res {
if self.smart_resolve_context_dependent_help(
&mut err,
span,
source,
res,
&path_str,
&base_error.fallback_label,
) {
// We do this to avoid losing a secondary span when we override the main error span.
self.r.add_typo_suggestion(&mut err, typo_sugg, ident_span);
return (err, candidates);
}
}
let is_macro =
base_error.span.from_expansion() && base_error.span.desugaring_kind().is_none();
if !self.type_ascription_suggestion(&mut err, base_error.span) {
let mut fallback = false;
if let (
PathSource::Trait(AliasPossibility::Maybe),
Some(Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _)),
false,
) = (source, res, is_macro)
{
if let Some(bounds @ [_, .., _]) = self.diagnostic_metadata.current_trait_object {
fallback = true;
let spans: Vec<Span> = bounds
.iter()
.map(|bound| bound.span())
.filter(|&sp| sp != base_error.span)
.collect();
let start_span = bounds.iter().map(|bound| bound.span()).next().unwrap();
// `end_span` is the end of the poly trait ref (Foo + 'baz + Bar><)
let end_span = bounds.iter().map(|bound| bound.span()).last().unwrap();
// `last_bound_span` is the last bound of the poly trait ref (Foo + >'baz< + Bar)
let last_bound_span = spans.last().cloned().unwrap();
let mut multi_span: MultiSpan = spans.clone().into();
for sp in spans {
let msg = if sp == last_bound_span {
format!(
"...because of {these} bound{s}",
these = pluralize!("this", bounds.len() - 1),
s = pluralize!(bounds.len() - 1),
)
} else {
String::new()
};
multi_span.push_span_label(sp, msg);
}
multi_span
.push_span_label(base_error.span, "expected this type to be a trait...");
err.span_help(
multi_span,
"`+` is used to constrain a \"trait object\" type with lifetimes or \
auto-traits; structs and enums can't be bound in that way",
);
if bounds.iter().all(|bound| match bound {
ast::GenericBound::Outlives(_) => true,
ast::GenericBound::Trait(tr, _) => tr.span == base_error.span,
}) {
let mut sugg = vec![];
if base_error.span != start_span {
sugg.push((start_span.until(base_error.span), String::new()));
}
if base_error.span != end_span {
sugg.push((base_error.span.shrink_to_hi().to(end_span), String::new()));
}
err.multipart_suggestion(
"if you meant to use a type and not a trait here, remove the bounds",
sugg,
Applicability::MaybeIncorrect,
);
}
}
}
fallback |= self.restrict_assoc_type_in_where_clause(span, &mut err);
if !self.r.add_typo_suggestion(&mut err, typo_sugg, ident_span) {
fallback = true;
match self.diagnostic_metadata.current_let_binding {
Some((pat_sp, Some(ty_sp), None))
if ty_sp.contains(base_error.span) && base_error.could_be_expr =>
{
err.span_suggestion_short(
pat_sp.between(ty_sp),
"use `=` if you meant to assign",
" = ",
Applicability::MaybeIncorrect,
);
}
_ => {}
}
// If the trait has a single item (which wasn't matched by Levenshtein), suggest it
let suggestion = self.get_single_associated_item(&path, &source, is_expected);
self.r.add_typo_suggestion(&mut err, suggestion, ident_span);
}
if fallback {
// Fallback label.
err.span_label(base_error.span, base_error.fallback_label);
}
}
if let Some(err_code) = &err.code {
if err_code == &rustc_errors::error_code!(E0425) {
for label_rib in &self.label_ribs {
for (label_ident, node_id) in &label_rib.bindings {
if format!("'{}", ident) == label_ident.to_string() {
err.span_label(label_ident.span, "a label with a similar name exists");
if let PathSource::Expr(Some(Expr {
kind: ExprKind::Break(None, Some(_)),
..
})) = source
{
err.span_suggestion(
span,
"use the similarly named label",
label_ident.name,
Applicability::MaybeIncorrect,
);
// Do not lint against unused label when we suggest them.
self.diagnostic_metadata.unused_labels.remove(node_id);
}
}
}
}
} else if err_code == &rustc_errors::error_code!(E0412) {
if let Some(correct) = Self::likely_rust_type(path) {
err.span_suggestion(
span,
"perhaps you intended to use this type",
correct,
Applicability::MaybeIncorrect,
);
}
}
}
(err, candidates)
}
fn detect_assoct_type_constraint_meant_as_path(&self, base_span: Span, err: &mut Diagnostic) {
let Some(ty) = self.diagnostic_metadata.current_type_path else { return; };
let TyKind::Path(_, path) = &ty.kind else { return; };
for segment in &path.segments {
let Some(params) = &segment.args else { continue; };
let ast::GenericArgs::AngleBracketed(ref params) = params.deref() else { continue; };
for param in &params.args {
let ast::AngleBracketedArg::Constraint(constraint) = param else { continue; };
let ast::AssocConstraintKind::Bound { bounds } = &constraint.kind else {
continue;
};
for bound in bounds {
let ast::GenericBound::Trait(trait_ref, ast::TraitBoundModifier::None)
= bound else
{
continue;
};
if base_span == trait_ref.span {
err.span_suggestion_verbose(
constraint.ident.span.between(trait_ref.span),
"you might have meant to write a path instead of an associated type bound",
"::",
Applicability::MachineApplicable,
);
}
}
}
}
}
fn suggest_swapping_misplaced_self_ty_and_trait(
&mut self,
err: &mut Diagnostic,
source: PathSource<'_>,
res: Option<Res>,
span: Span,
) {
if let Some((trait_ref, self_ty)) =
self.diagnostic_metadata.currently_processing_impl_trait.clone()
&& let TyKind::Path(_, self_ty_path) = &self_ty.kind
&& let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
self.resolve_path(&Segment::from_path(self_ty_path), Some(TypeNS), None)
&& let ModuleKind::Def(DefKind::Trait, ..) = module.kind
&& trait_ref.path.span == span
&& let PathSource::Trait(_) = source
&& let Some(Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _)) = res
&& let Ok(self_ty_str) =
self.r.session.source_map().span_to_snippet(self_ty.span)
&& let Ok(trait_ref_str) =
self.r.session.source_map().span_to_snippet(trait_ref.path.span)
{
err.multipart_suggestion(
"`impl` items mention the trait being implemented first and the type it is being implemented for second",
vec![(trait_ref.path.span, self_ty_str), (self_ty.span, trait_ref_str)],
Applicability::MaybeIncorrect,
);
}
}
fn get_single_associated_item(
&mut self,
path: &[Segment],
source: &PathSource<'_>,
filter_fn: &impl Fn(Res) -> bool,
) -> Option<TypoSuggestion> {
if let crate::PathSource::TraitItem(_) = source {
let mod_path = &path[..path.len() - 1];
if let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
self.resolve_path(mod_path, None, None)
{
let resolutions = self.r.resolutions(module).borrow();
let targets: Vec<_> =
resolutions
.iter()
.filter_map(|(key, resolution)| {
resolution.borrow().binding.map(|binding| binding.res()).and_then(
|res| if filter_fn(res) { Some((key, res)) } else { None },
)
})
.collect();
if targets.len() == 1 {
let target = targets[0];
return Some(TypoSuggestion::single_item_from_res(
target.0.ident.name,
target.1,
));
}
}
}
None
}
/// Given `where <T as Bar>::Baz: String`, suggest `where T: Bar<Baz = String>`.
fn restrict_assoc_type_in_where_clause(&mut self, span: Span, err: &mut Diagnostic) -> bool {
// Detect that we are actually in a `where` predicate.
let (bounded_ty, bounds, where_span) =
if let Some(ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
bounded_ty,
bound_generic_params,
bounds,
span,
})) = self.diagnostic_metadata.current_where_predicate
{
if !bound_generic_params.is_empty() {
return false;
}
(bounded_ty, bounds, span)
} else {
return false;
};
// Confirm that the target is an associated type.
let (ty, position, path) = if let ast::TyKind::Path(
Some(ast::QSelf { ty, position, .. }),
path,
) = &bounded_ty.kind
{
// use this to verify that ident is a type param.
let Some(partial_res) = self.r.partial_res_map.get(&bounded_ty.id) else {
return false;
};
if !(matches!(
partial_res.base_res(),
hir::def::Res::Def(hir::def::DefKind::AssocTy, _)
) && partial_res.unresolved_segments() == 0)
{
return false;
}
(ty, position, path)
} else {
return false;
};
let peeled_ty = ty.peel_refs();
if let ast::TyKind::Path(None, type_param_path) = &peeled_ty.kind {
// Confirm that the `SelfTy` is a type parameter.
let Some(partial_res) = self.r.partial_res_map.get(&peeled_ty.id) else {
return false;
};
if !(matches!(
partial_res.base_res(),
hir::def::Res::Def(hir::def::DefKind::TyParam, _)
) && partial_res.unresolved_segments() == 0)
{
return false;
}
if let (
[ast::PathSegment { ident: constrain_ident, args: None, .. }],
[ast::GenericBound::Trait(poly_trait_ref, ast::TraitBoundModifier::None)],
) = (&type_param_path.segments[..], &bounds[..])
{
if let [ast::PathSegment { ident, args: None, .. }] =
&poly_trait_ref.trait_ref.path.segments[..]
{
if ident.span == span {
err.span_suggestion_verbose(
*where_span,
&format!("constrain the associated type to `{}`", ident),
format!(
"{}: {}<{} = {}>",
self.r
.session
.source_map()
.span_to_snippet(ty.span) // Account for `<&'a T as Foo>::Bar`.
.unwrap_or_else(|_| constrain_ident.to_string()),
path.segments[..*position]
.iter()
.map(|segment| path_segment_to_string(segment))
.collect::<Vec<_>>()
.join("::"),
path.segments[*position..]
.iter()
.map(|segment| path_segment_to_string(segment))
.collect::<Vec<_>>()
.join("::"),
ident,
),
Applicability::MaybeIncorrect,
);
}
return true;
}
}
}
false
}
/// Check if the source is call expression and the first argument is `self`. If true,
/// return the span of whole call and the span for all arguments expect the first one (`self`).
fn call_has_self_arg(&self, source: PathSource<'_>) -> Option<(Span, Option<Span>)> {
let mut has_self_arg = None;
if let PathSource::Expr(Some(parent)) = source {
match &parent.kind {
ExprKind::Call(_, args) if !args.is_empty() => {
let mut expr_kind = &args[0].kind;
loop {
match expr_kind {
ExprKind::Path(_, arg_name) if arg_name.segments.len() == 1 => {
if arg_name.segments[0].ident.name == kw::SelfLower {
let call_span = parent.span;
let tail_args_span = if args.len() > 1 {
Some(Span::new(
args[1].span.lo(),
args.last().unwrap().span.hi(),
call_span.ctxt(),
None,
))
} else {
None
};
has_self_arg = Some((call_span, tail_args_span));
}
break;
}
ExprKind::AddrOf(_, _, expr) => expr_kind = &expr.kind,
_ => break,
}
}
}
_ => (),
}
};
has_self_arg
}
fn followed_by_brace(&self, span: Span) -> (bool, Option<Span>) {
// HACK(estebank): find a better way to figure out that this was a
// parser issue where a struct literal is being used on an expression
// where a brace being opened means a block is being started. Look
// ahead for the next text to see if `span` is followed by a `{`.
let sm = self.r.session.source_map();
let mut sp = span;
loop {
sp = sm.next_point(sp);
match sm.span_to_snippet(sp) {
Ok(ref snippet) => {
if snippet.chars().any(|c| !c.is_whitespace()) {
break;
}
}
_ => break,
}
}
let followed_by_brace = matches!(sm.span_to_snippet(sp), Ok(ref snippet) if snippet == "{");
// In case this could be a struct literal that needs to be surrounded
// by parentheses, find the appropriate span.
let mut i = 0;
let mut closing_brace = None;
loop {
sp = sm.next_point(sp);
match sm.span_to_snippet(sp) {
Ok(ref snippet) => {
if snippet == "}" {
closing_brace = Some(span.to(sp));
break;
}
}
_ => break,
}
i += 1;
// The bigger the span, the more likely we're incorrect --
// bound it to 100 chars long.
if i > 100 {
break;
}
}
(followed_by_brace, closing_brace)
}
/// Provides context-dependent help for errors reported by the `smart_resolve_path_fragment`
/// function.
/// Returns `true` if able to provide context-dependent help.
fn smart_resolve_context_dependent_help(
&mut self,
err: &mut Diagnostic,
span: Span,
source: PathSource<'_>,
res: Res,
path_str: &str,
fallback_label: &str,
) -> bool {
let ns = source.namespace();
let is_expected = &|res| source.is_expected(res);
let path_sep = |err: &mut Diagnostic, expr: &Expr, kind: DefKind| {
const MESSAGE: &str = "use the path separator to refer to an item";
let (lhs_span, rhs_span) = match &expr.kind {
ExprKind::Field(base, ident) => (base.span, ident.span),
ExprKind::MethodCall(_, receiver, _, span) => (receiver.span, *span),
_ => return false,
};
if lhs_span.eq_ctxt(rhs_span) {
err.span_suggestion(
lhs_span.between(rhs_span),
MESSAGE,
"::",
Applicability::MaybeIncorrect,
);
true
} else if kind == DefKind::Struct
&& let Some(lhs_source_span) = lhs_span.find_ancestor_inside(expr.span)
&& let Ok(snippet) = self.r.session.source_map().span_to_snippet(lhs_source_span)
{
// The LHS is a type that originates from a macro call.
// We have to add angle brackets around it.
err.span_suggestion_verbose(
lhs_source_span.until(rhs_span),
MESSAGE,
format!("<{snippet}>::"),
Applicability::MaybeIncorrect,
);
true
} else {
// Either we were unable to obtain the source span / the snippet or
// the LHS originates from a macro call and it is not a type and thus
// there is no way to replace `.` with `::` and still somehow suggest
// valid Rust code.
false
}
};
let find_span = |source: &PathSource<'_>, err: &mut Diagnostic| {
match source {
PathSource::Expr(Some(Expr { span, kind: ExprKind::Call(_, _), .. }))
| PathSource::TupleStruct(span, _) => {
// We want the main underline to cover the suggested code as well for
// cleaner output.
err.set_span(*span);
*span
}
_ => span,
}
};
let mut bad_struct_syntax_suggestion = |def_id: DefId| {
let (followed_by_brace, closing_brace) = self.followed_by_brace(span);
match source {
PathSource::Expr(Some(
parent @ Expr { kind: ExprKind::Field(..) | ExprKind::MethodCall(..), .. },
)) if path_sep(err, &parent, DefKind::Struct) => {}
PathSource::Expr(
None
| Some(Expr {
kind:
ExprKind::Path(..)
| ExprKind::Binary(..)
| ExprKind::Unary(..)
| ExprKind::If(..)
| ExprKind::While(..)
| ExprKind::ForLoop(..)
| ExprKind::Match(..),
..
}),
) if followed_by_brace => {
if let Some(sp) = closing_brace {
err.span_label(span, fallback_label);
err.multipart_suggestion(
"surround the struct literal with parentheses",
vec![
(sp.shrink_to_lo(), "(".to_string()),
(sp.shrink_to_hi(), ")".to_string()),
],
Applicability::MaybeIncorrect,
);
} else {
err.span_label(
span, // Note the parentheses surrounding the suggestion below
format!(
"you might want to surround a struct literal with parentheses: \
`({} {{ /* fields */ }})`?",
path_str
),
);
}
}
PathSource::Expr(_) | PathSource::TupleStruct(..) | PathSource::Pat => {
let span = find_span(&source, err);
if let Some(span) = self.def_span(def_id) {
err.span_label(span, &format!("`{}` defined here", path_str));
}
let (tail, descr, applicability) = match source {
PathSource::Pat | PathSource::TupleStruct(..) => {
("", "pattern", Applicability::MachineApplicable)
}
_ => (": val", "literal", Applicability::HasPlaceholders),
};
let (fields, applicability) = match self.r.field_names.get(&def_id) {
Some(fields) => (
fields
.iter()
.map(|f| format!("{}{}", f.node, tail))
.collect::<Vec<String>>()
.join(", "),
applicability,
),
None => ("/* fields */".to_string(), Applicability::HasPlaceholders),
};
let pad = match self.r.field_names.get(&def_id) {
Some(fields) if fields.is_empty() => "",
_ => " ",
};
err.span_suggestion(
span,
&format!("use struct {} syntax instead", descr),
format!("{path_str} {{{pad}{fields}{pad}}}"),
applicability,
);
}
_ => {
err.span_label(span, fallback_label);
}
}
};
match (res, source) {
(
Res::Def(DefKind::Macro(MacroKind::Bang), _),
PathSource::Expr(Some(Expr {
kind: ExprKind::Index(..) | ExprKind::Call(..), ..
}))
| PathSource::Struct,
) => {
err.span_label(span, fallback_label);
err.span_suggestion_verbose(
span.shrink_to_hi(),
"use `!` to invoke the macro",
"!",
Applicability::MaybeIncorrect,
);
if path_str == "try" && span.rust_2015() {
err.note("if you want the `try` keyword, you need Rust 2018 or later");
}
}
(Res::Def(DefKind::Macro(MacroKind::Bang), _), _) => {
err.span_label(span, fallback_label);
}
(Res::Def(DefKind::TyAlias, def_id), PathSource::Trait(_)) => {
err.span_label(span, "type aliases cannot be used as traits");
if self.r.session.is_nightly_build() {
let msg = "you might have meant to use `#![feature(trait_alias)]` instead of a \
`type` alias";
if let Some(span) = self.def_span(def_id) {
if let Ok(snip) = self.r.session.source_map().span_to_snippet(span) {
// The span contains a type alias so we should be able to
// replace `type` with `trait`.
let snip = snip.replacen("type", "trait", 1);
err.span_suggestion(span, msg, snip, Applicability::MaybeIncorrect);
} else {
err.span_help(span, msg);
}
} else {
err.help(msg);
}
}
}
(
Res::Def(kind @ (DefKind::Mod | DefKind::Trait), _),
PathSource::Expr(Some(parent)),
) => {
if !path_sep(err, &parent, kind) {
return false;
}
}
(
Res::Def(DefKind::Enum, def_id),
PathSource::TupleStruct(..) | PathSource::Expr(..),
) => {
if self
.diagnostic_metadata
.current_type_ascription
.last()
.map(|sp| {
self.r
.session
.parse_sess
.type_ascription_path_suggestions
.borrow()
.contains(&sp)
})
.unwrap_or(false)
{
err.downgrade_to_delayed_bug();
// We already suggested changing `:` into `::` during parsing.
return false;
}
self.suggest_using_enum_variant(err, source, def_id, span);
}
(Res::Def(DefKind::Struct, def_id), source) if ns == ValueNS => {
let (ctor_def, ctor_vis, fields) =
if let Some(struct_ctor) = self.r.struct_constructors.get(&def_id).cloned() {
if let PathSource::Expr(Some(parent)) = source {
if let ExprKind::Field(..) | ExprKind::MethodCall(..) = parent.kind {
bad_struct_syntax_suggestion(def_id);
return true;
}
}
struct_ctor
} else {
bad_struct_syntax_suggestion(def_id);
return true;
};
let is_accessible = self.r.is_accessible_from(ctor_vis, self.parent_scope.module);
if !is_expected(ctor_def) || is_accessible {
return true;
}
let field_spans = match source {
// e.g. `if let Enum::TupleVariant(field1, field2) = _`
PathSource::TupleStruct(_, pattern_spans) => {
err.set_primary_message(
"cannot match against a tuple struct which contains private fields",
);
// Use spans of the tuple struct pattern.
Some(Vec::from(pattern_spans))
}
// e.g. `let _ = Enum::TupleVariant(field1, field2);`
_ if source.is_call() => {
err.set_primary_message(
"cannot initialize a tuple struct which contains private fields",
);
// Use spans of the tuple struct definition.
self.r
.field_names
.get(&def_id)
.map(|fields| fields.iter().map(|f| f.span).collect::<Vec<_>>())
}
_ => None,
};
if let Some(spans) =
field_spans.filter(|spans| spans.len() > 0 && fields.len() == spans.len())
{
let non_visible_spans: Vec<Span> = iter::zip(&fields, &spans)
.filter(|(vis, _)| {
!self.r.is_accessible_from(**vis, self.parent_scope.module)
})
.map(|(_, span)| *span)
.collect();
if non_visible_spans.len() > 0 {
let mut m: MultiSpan = non_visible_spans.clone().into();
non_visible_spans
.into_iter()
.for_each(|s| m.push_span_label(s, "private field"));
err.span_note(m, "constructor is not visible here due to private fields");
}
return true;
}
err.span_label(span, "constructor is not visible here due to private fields");
}
(
Res::Def(
DefKind::Union | DefKind::Variant | DefKind::Ctor(_, CtorKind::Fictive),
def_id,
),
_,
) if ns == ValueNS => {
bad_struct_syntax_suggestion(def_id);
}
(Res::Def(DefKind::Ctor(_, CtorKind::Const), def_id), _) if ns == ValueNS => {
match source {
PathSource::Expr(_) | PathSource::TupleStruct(..) | PathSource::Pat => {
let span = find_span(&source, err);
if let Some(span) = self.def_span(def_id) {
err.span_label(span, &format!("`{}` defined here", path_str));
}
err.span_suggestion(
span,
"use this syntax instead",
path_str,
Applicability::MaybeIncorrect,
);
}
_ => return false,
}
}
(Res::Def(DefKind::Ctor(_, CtorKind::Fn), def_id), _) if ns == ValueNS => {
if let Some(span) = self.def_span(def_id) {
err.span_label(span, &format!("`{}` defined here", path_str));
}
let fields = self.r.field_names.get(&def_id).map_or_else(
|| "/* fields */".to_string(),
|fields| vec!["_"; fields.len()].join(", "),
);
err.span_suggestion(
span,
"use the tuple variant pattern syntax instead",
format!("{}({})", path_str, fields),
Applicability::HasPlaceholders,
);
}
(Res::SelfTy { .. }, _) if ns == ValueNS => {
err.span_label(span, fallback_label);
err.note("can't use `Self` as a constructor, you must use the implemented struct");
}
(Res::Def(DefKind::TyAlias | DefKind::AssocTy, _), _) if ns == ValueNS => {
err.note("can't use a type alias as a constructor");
}
_ => return false,
}
true
}
/// Given the target `ident` and `kind`, search for the similarly named associated item
/// in `self.current_trait_ref`.
pub(crate) fn find_similarly_named_assoc_item(
&mut self,
ident: Symbol,
kind: &AssocItemKind,
) -> Option<Symbol> {
let (module, _) = self.current_trait_ref.as_ref()?;
if ident == kw::Underscore {
// We do nothing for `_`.
return None;
}
let resolutions = self.r.resolutions(module);
let targets = resolutions
.borrow()
.iter()
.filter_map(|(key, res)| res.borrow().binding.map(|binding| (key, binding.res())))
.filter(|(_, res)| match (kind, res) {
(AssocItemKind::Const(..), Res::Def(DefKind::AssocConst, _)) => true,
(AssocItemKind::Fn(_), Res::Def(DefKind::AssocFn, _)) => true,
(AssocItemKind::TyAlias(..), Res::Def(DefKind::AssocTy, _)) => true,
_ => false,
})
.map(|(key, _)| key.ident.name)
.collect::<Vec<_>>();
find_best_match_for_name(&targets, ident, None)
}
fn lookup_assoc_candidate<FilterFn>(
&mut self,
ident: Ident,
ns: Namespace,
filter_fn: FilterFn,
) -> Option<AssocSuggestion>
where
FilterFn: Fn(Res) -> bool,
{
fn extract_node_id(t: &Ty) -> Option<NodeId> {
match t.kind {
TyKind::Path(None, _) => Some(t.id),
TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
// This doesn't handle the remaining `Ty` variants as they are not
// that commonly the self_type, it might be interesting to provide
// support for those in future.
_ => None,
}
}
// Fields are generally expected in the same contexts as locals.
if filter_fn(Res::Local(ast::DUMMY_NODE_ID)) {
if let Some(node_id) =
self.diagnostic_metadata.current_self_type.as_ref().and_then(extract_node_id)
{
// Look for a field with the same name in the current self_type.
if let Some(resolution) = self.r.partial_res_map.get(&node_id) {
match resolution.base_res() {
Res::Def(DefKind::Struct | DefKind::Union, did)
if resolution.unresolved_segments() == 0 =>
{
if let Some(field_names) = self.r.field_names.get(&did) {
if field_names
.iter()
.any(|&field_name| ident.name == field_name.node)
{
return Some(AssocSuggestion::Field);
}
}
}
_ => {}
}
}
}
}
if let Some(items) = self.diagnostic_metadata.current_trait_assoc_items {
for assoc_item in items {
if assoc_item.ident == ident {
return Some(match &assoc_item.kind {
ast::AssocItemKind::Const(..) => AssocSuggestion::AssocConst,
ast::AssocItemKind::Fn(box ast::Fn { sig, .. }) if sig.decl.has_self() => {
AssocSuggestion::MethodWithSelf
}
ast::AssocItemKind::Fn(..) => AssocSuggestion::AssocFn,
ast::AssocItemKind::TyAlias(..) => AssocSuggestion::AssocType,
ast::AssocItemKind::MacCall(_) => continue,
});
}
}
}
// Look for associated items in the current trait.
if let Some((module, _)) = self.current_trait_ref {
if let Ok(binding) = self.r.maybe_resolve_ident_in_module(
ModuleOrUniformRoot::Module(module),
ident,
ns,
&self.parent_scope,
) {
let res = binding.res();
if filter_fn(res) {
if self.r.has_self.contains(&res.def_id()) {
return Some(AssocSuggestion::MethodWithSelf);
} else {
match res {
Res::Def(DefKind::AssocFn, _) => return Some(AssocSuggestion::AssocFn),
Res::Def(DefKind::AssocConst, _) => {
return Some(AssocSuggestion::AssocConst);
}
Res::Def(DefKind::AssocTy, _) => {
return Some(AssocSuggestion::AssocType);
}
_ => {}
}
}
}
}
}
None
}
fn lookup_typo_candidate(
&mut self,
path: &[Segment],
ns: Namespace,
filter_fn: &impl Fn(Res) -> bool,
) -> Option<TypoSuggestion> {
let mut names = Vec::new();
if path.len() == 1 {
// Search in lexical scope.
// Walk backwards up the ribs in scope and collect candidates.
for rib in self.ribs[ns].iter().rev() {
// Locals and type parameters
for (ident, &res) in &rib.bindings {
if filter_fn(res) {
names.push(TypoSuggestion::typo_from_res(ident.name, res));
}
}
// Items in scope
if let RibKind::ModuleRibKind(module) = rib.kind {
// Items from this module
self.r.add_module_candidates(module, &mut names, &filter_fn);
if let ModuleKind::Block = module.kind {
// We can see through blocks
} else {
// Items from the prelude
if !module.no_implicit_prelude {
let extern_prelude = self.r.extern_prelude.clone();
names.extend(extern_prelude.iter().flat_map(|(ident, _)| {
self.r.crate_loader.maybe_process_path_extern(ident.name).and_then(
|crate_id| {
let crate_mod =
Res::Def(DefKind::Mod, crate_id.as_def_id());
if filter_fn(crate_mod) {
Some(TypoSuggestion::typo_from_res(
ident.name, crate_mod,
))
} else {
None
}
},
)
}));
if let Some(prelude) = self.r.prelude {
self.r.add_module_candidates(prelude, &mut names, &filter_fn);
}
}
break;
}
}
}
// Add primitive types to the mix
if filter_fn(Res::PrimTy(PrimTy::Bool)) {
names.extend(PrimTy::ALL.iter().map(|prim_ty| {
TypoSuggestion::typo_from_res(prim_ty.name(), Res::PrimTy(*prim_ty))
}))
}
} else {
// Search in module.
let mod_path = &path[..path.len() - 1];
if let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
self.resolve_path(mod_path, Some(TypeNS), None)
{
self.r.add_module_candidates(module, &mut names, &filter_fn);
}
}
let name = path[path.len() - 1].ident.name;
// Make sure error reporting is deterministic.
names.sort_by(|a, b| a.candidate.as_str().partial_cmp(b.candidate.as_str()).unwrap());
match find_best_match_for_name(
&names.iter().map(|suggestion| suggestion.candidate).collect::<Vec<Symbol>>(),
name,
None,
) {
Some(found) if found != name => {
names.into_iter().find(|suggestion| suggestion.candidate == found)
}
_ => None,
}
}
// Returns the name of the Rust type approximately corresponding to
// a type name in another programming language.
fn likely_rust_type(path: &[Segment]) -> Option<Symbol> {
let name = path[path.len() - 1].ident.as_str();
// Common Java types
Some(match name {
"byte" => sym::u8, // In Java, bytes are signed, but in practice one almost always wants unsigned bytes.
"short" => sym::i16,
"Bool" => sym::bool,
"Boolean" => sym::bool,
"boolean" => sym::bool,
"int" => sym::i32,
"long" => sym::i64,
"float" => sym::f32,
"double" => sym::f64,
_ => return None,
})
}
/// Only used in a specific case of type ascription suggestions
fn get_colon_suggestion_span(&self, start: Span) -> Span {
let sm = self.r.session.source_map();
start.to(sm.next_point(start))
}
fn type_ascription_suggestion(&self, err: &mut Diagnostic, base_span: Span) -> bool {
let sm = self.r.session.source_map();
let base_snippet = sm.span_to_snippet(base_span);
if let Some(&sp) = self.diagnostic_metadata.current_type_ascription.last() {
if let Ok(snippet) = sm.span_to_snippet(sp) {
let len = snippet.trim_end().len() as u32;
if snippet.trim() == ":" {
let colon_sp =
sp.with_lo(sp.lo() + BytePos(len - 1)).with_hi(sp.lo() + BytePos(len));
let mut show_label = true;
if sm.is_multiline(sp) {
err.span_suggestion_short(
colon_sp,
"maybe you meant to write `;` here",
";",
Applicability::MaybeIncorrect,
);
} else {
let after_colon_sp =
self.get_colon_suggestion_span(colon_sp.shrink_to_hi());
if snippet.len() == 1 {
// `foo:bar`
err.span_suggestion(
colon_sp,
"maybe you meant to write a path separator here",
"::",
Applicability::MaybeIncorrect,
);
show_label = false;
if !self
.r
.session
.parse_sess
.type_ascription_path_suggestions
.borrow_mut()
.insert(colon_sp)
{
err.downgrade_to_delayed_bug();
}
}
if let Ok(base_snippet) = base_snippet {
let mut sp = after_colon_sp;
for _ in 0..100 {
// Try to find an assignment
sp = sm.next_point(sp);
let snippet = sm.span_to_snippet(sp.to(sm.next_point(sp)));
match snippet {
Ok(ref x) if x.as_str() == "=" => {
err.span_suggestion(
base_span,
"maybe you meant to write an assignment here",
format!("let {}", base_snippet),
Applicability::MaybeIncorrect,
);
show_label = false;
break;
}
Ok(ref x) if x.as_str() == "\n" => break,
Err(_) => break,
Ok(_) => {}
}
}
}
}
if show_label {
err.span_label(
base_span,
"expecting a type here because of type ascription",
);
}
return show_label;
}
}
}
false
}
fn find_module(&mut self, def_id: DefId) -> Option<(Module<'a>, ImportSuggestion)> {
let mut result = None;
let mut seen_modules = FxHashSet::default();
let mut worklist = vec![(self.r.graph_root, Vec::new())];
while let Some((in_module, path_segments)) = worklist.pop() {
// abort if the module is already found
if result.is_some() {
break;
}
in_module.for_each_child(self.r, |_, ident, _, name_binding| {
// abort if the module is already found or if name_binding is private external
if result.is_some() || !name_binding.vis.is_visible_locally() {
return;
}
if let Some(module) = name_binding.module() {
// form the path
let mut path_segments = path_segments.clone();
path_segments.push(ast::PathSegment::from_ident(ident));
let module_def_id = module.def_id();
if module_def_id == def_id {
let path =
Path { span: name_binding.span, segments: path_segments, tokens: None };
result = Some((
module,
ImportSuggestion {
did: Some(def_id),
descr: "module",
path,
accessible: true,
note: None,
},
));
} else {
// add the module to the lookup
if seen_modules.insert(module_def_id) {
worklist.push((module, path_segments));
}
}
}
});
}
result
}
fn collect_enum_ctors(&mut self, def_id: DefId) -> Option<Vec<(Path, DefId, CtorKind)>> {
self.find_module(def_id).map(|(enum_module, enum_import_suggestion)| {
let mut variants = Vec::new();
enum_module.for_each_child(self.r, |_, ident, _, name_binding| {
if let Res::Def(DefKind::Ctor(CtorOf::Variant, kind), def_id) = name_binding.res() {
let mut segms = enum_import_suggestion.path.segments.clone();
segms.push(ast::PathSegment::from_ident(ident));
let path = Path { span: name_binding.span, segments: segms, tokens: None };
variants.push((path, def_id, kind));
}
});
variants
})
}
/// Adds a suggestion for using an enum's variant when an enum is used instead.
fn suggest_using_enum_variant(
&mut self,
err: &mut Diagnostic,
source: PathSource<'_>,
def_id: DefId,
span: Span,
) {
let Some(variants) = self.collect_enum_ctors(def_id) else {
err.note("you might have meant to use one of the enum's variants");
return;
};
let suggest_only_tuple_variants =
matches!(source, PathSource::TupleStruct(..)) || source.is_call();
if suggest_only_tuple_variants {
// Suggest only tuple variants regardless of whether they have fields and do not
// suggest path with added parentheses.
let suggestable_variants = variants
.iter()
.filter(|(.., kind)| *kind == CtorKind::Fn)
.map(|(variant, ..)| path_names_to_string(variant))
.collect::<Vec<_>>();
let non_suggestable_variant_count = variants.len() - suggestable_variants.len();
let source_msg = if source.is_call() {
"to construct"
} else if matches!(source, PathSource::TupleStruct(..)) {
"to match against"
} else {
unreachable!()
};
if !suggestable_variants.is_empty() {
let msg = if non_suggestable_variant_count == 0 && suggestable_variants.len() == 1 {
format!("try {} the enum's variant", source_msg)
} else {
format!("try {} one of the enum's variants", source_msg)
};
err.span_suggestions(
span,
&msg,
suggestable_variants.into_iter(),
Applicability::MaybeIncorrect,
);
}
// If the enum has no tuple variants..
if non_suggestable_variant_count == variants.len() {
err.help(&format!("the enum has no tuple variants {}", source_msg));
}
// If there are also non-tuple variants..
if non_suggestable_variant_count == 1 {
err.help(&format!(
"you might have meant {} the enum's non-tuple variant",
source_msg
));
} else if non_suggestable_variant_count >= 1 {
err.help(&format!(
"you might have meant {} one of the enum's non-tuple variants",
source_msg
));
}
} else {
let needs_placeholder = |def_id: DefId, kind: CtorKind| {
let has_no_fields = self.r.field_names.get(&def_id).map_or(false, |f| f.is_empty());
match kind {
CtorKind::Const => false,
CtorKind::Fn | CtorKind::Fictive if has_no_fields => false,
_ => true,
}
};
let suggestable_variants = variants
.iter()
.filter(|(_, def_id, kind)| !needs_placeholder(*def_id, *kind))
.map(|(variant, _, kind)| (path_names_to_string(variant), kind))
.map(|(variant, kind)| match kind {
CtorKind::Const => variant,
CtorKind::Fn => format!("({}())", variant),
CtorKind::Fictive => format!("({} {{}})", variant),
})
.collect::<Vec<_>>();
let no_suggestable_variant = suggestable_variants.is_empty();
if !no_suggestable_variant {
let msg = if suggestable_variants.len() == 1 {
"you might have meant to use the following enum variant"
} else {
"you might have meant to use one of the following enum variants"
};
err.span_suggestions(
span,
msg,
suggestable_variants.into_iter(),
Applicability::MaybeIncorrect,
);
}
let suggestable_variants_with_placeholders = variants
.iter()
.filter(|(_, def_id, kind)| needs_placeholder(*def_id, *kind))
.map(|(variant, _, kind)| (path_names_to_string(variant), kind))
.filter_map(|(variant, kind)| match kind {
CtorKind::Fn => Some(format!("({}(/* fields */))", variant)),
CtorKind::Fictive => Some(format!("({} {{ /* fields */ }})", variant)),
_ => None,
})
.collect::<Vec<_>>();
if !suggestable_variants_with_placeholders.is_empty() {
let msg =
match (no_suggestable_variant, suggestable_variants_with_placeholders.len()) {
(true, 1) => "the following enum variant is available",
(true, _) => "the following enum variants are available",
(false, 1) => "alternatively, the following enum variant is available",
(false, _) => {
"alternatively, the following enum variants are also available"
}
};
err.span_suggestions(
span,
msg,
suggestable_variants_with_placeholders.into_iter(),
Applicability::HasPlaceholders,
);
}
};
if def_id.is_local() {
if let Some(span) = self.def_span(def_id) {
err.span_note(span, "the enum is defined here");
}
}
}
pub(crate) fn report_missing_type_error(
&self,
path: &[Segment],
) -> Option<(Span, &'static str, String, Applicability)> {
let (ident, span) = match path {
[segment] if !segment.has_generic_args && segment.ident.name != kw::SelfUpper => {
(segment.ident.to_string(), segment.ident.span)
}
_ => return None,
};
let mut iter = ident.chars().map(|c| c.is_uppercase());
let single_uppercase_char =
matches!(iter.next(), Some(true)) && matches!(iter.next(), None);
if !self.diagnostic_metadata.currently_processing_generics && !single_uppercase_char {
return None;
}
match (self.diagnostic_metadata.current_item, single_uppercase_char, self.diagnostic_metadata.currently_processing_generics) {
(Some(Item { kind: ItemKind::Fn(..), ident, .. }), _, _) if ident.name == sym::main => {
// Ignore `fn main()` as we don't want to suggest `fn main<T>()`
}
(
Some(Item {
kind:
kind @ ItemKind::Fn(..)
| kind @ ItemKind::Enum(..)
| kind @ ItemKind::Struct(..)
| kind @ ItemKind::Union(..),
..
}),
true, _
)
// Without the 2nd `true`, we'd suggest `impl <T>` for `impl T` when a type `T` isn't found
| (Some(Item { kind: kind @ ItemKind::Impl(..), .. }), true, true)
| (Some(Item { kind, .. }), false, _) => {
// Likely missing type parameter.
if let Some(generics) = kind.generics() {
if span.overlaps(generics.span) {
// Avoid the following:
// error[E0405]: cannot find trait `A` in this scope
// --> $DIR/typo-suggestion-named-underscore.rs:CC:LL
// |
// L | fn foo<T: A>(x: T) {} // Shouldn't suggest underscore
// | ^- help: you might be missing a type parameter: `, A`
// | |
// | not found in this scope
return None;
}
let msg = "you might be missing a type parameter";
let (span, sugg) = if let [.., param] = &generics.params[..] {
let span = if let [.., bound] = &param.bounds[..] {
bound.span()
} else if let GenericParam {
kind: GenericParamKind::Const { ty, kw_span: _, default }, ..
} = param {
default.as_ref().map(|def| def.value.span).unwrap_or(ty.span)
} else {
param.ident.span
};
(span, format!(", {}", ident))
} else {
(generics.span, format!("<{}>", ident))
};
// Do not suggest if this is coming from macro expansion.
if span.can_be_used_for_suggestions() {
return Some((
span.shrink_to_hi(),
msg,
sugg,
Applicability::MaybeIncorrect,
));
}
}
}
_ => {}
}
None
}
/// Given the target `label`, search the `rib_index`th label rib for similarly named labels,
/// optionally returning the closest match and whether it is reachable.
pub(crate) fn suggestion_for_label_in_rib(
&self,
rib_index: usize,
label: Ident,
) -> Option<LabelSuggestion> {
// Are ribs from this `rib_index` within scope?
let within_scope = self.is_label_valid_from_rib(rib_index);
let rib = &self.label_ribs[rib_index];
let names = rib
.bindings
.iter()
.filter(|(id, _)| id.span.eq_ctxt(label.span))
.map(|(id, _)| id.name)
.collect::<Vec<Symbol>>();
find_best_match_for_name(&names, label.name, None).map(|symbol| {
// Upon finding a similar name, get the ident that it was from - the span
// contained within helps make a useful diagnostic. In addition, determine
// whether this candidate is within scope.
let (ident, _) = rib.bindings.iter().find(|(ident, _)| ident.name == symbol).unwrap();
(*ident, within_scope)
})
}
pub(crate) fn maybe_report_lifetime_uses(
&mut self,
generics_span: Span,
params: &[ast::GenericParam],
) {
for (param_index, param) in params.iter().enumerate() {
let GenericParamKind::Lifetime = param.kind else { continue };
let def_id = self.r.local_def_id(param.id);
let use_set = self.lifetime_uses.remove(&def_id);
debug!(
"Use set for {:?}({:?} at {:?}) is {:?}",
def_id, param.ident, param.ident.span, use_set
);
let deletion_span = || {
if params.len() == 1 {
// if sole lifetime, remove the entire `<>` brackets
generics_span
} else if param_index == 0 {
// if removing within `<>` brackets, we also want to
// delete a leading or trailing comma as appropriate
param.span().to(params[param_index + 1].span().shrink_to_lo())
} else {
// if removing within `<>` brackets, we also want to
// delete a leading or trailing comma as appropriate
params[param_index - 1].span().shrink_to_hi().to(param.span())
}
};
match use_set {
Some(LifetimeUseSet::Many) => {}
Some(LifetimeUseSet::One { use_span, use_ctxt }) => {
debug!(?param.ident, ?param.ident.span, ?use_span);
let elidable = matches!(use_ctxt, LifetimeCtxt::Rptr);
let deletion_span = deletion_span();
self.r.lint_buffer.buffer_lint_with_diagnostic(
lint::builtin::SINGLE_USE_LIFETIMES,
param.id,
param.ident.span,
&format!("lifetime parameter `{}` only used once", param.ident),
lint::BuiltinLintDiagnostics::SingleUseLifetime {
param_span: param.ident.span,
use_span: Some((use_span, elidable)),
deletion_span,
},
);
}
None => {
debug!(?param.ident, ?param.ident.span);
let deletion_span = deletion_span();
self.r.lint_buffer.buffer_lint_with_diagnostic(
lint::builtin::UNUSED_LIFETIMES,
param.id,
param.ident.span,
&format!("lifetime parameter `{}` never used", param.ident),
lint::BuiltinLintDiagnostics::SingleUseLifetime {
param_span: param.ident.span,
use_span: None,
deletion_span,
},
);
}
}
}
}
pub(crate) fn emit_undeclared_lifetime_error(
&self,
lifetime_ref: &ast::Lifetime,
outer_lifetime_ref: Option<Ident>,
) {
debug_assert_ne!(lifetime_ref.ident.name, kw::UnderscoreLifetime);
let mut err = if let Some(outer) = outer_lifetime_ref {
let mut err = struct_span_err!(
self.r.session,
lifetime_ref.ident.span,
E0401,
"can't use generic parameters from outer item",
);
err.span_label(lifetime_ref.ident.span, "use of generic parameter from outer item");
err.span_label(outer.span, "lifetime parameter from outer item");
err
} else {
let mut err = struct_span_err!(
self.r.session,
lifetime_ref.ident.span,
E0261,
"use of undeclared lifetime name `{}`",
lifetime_ref.ident
);
err.span_label(lifetime_ref.ident.span, "undeclared lifetime");
err
};
self.suggest_introducing_lifetime(
&mut err,
Some(lifetime_ref.ident.name.as_str()),
|err, _, span, message, suggestion| {
err.span_suggestion(span, message, suggestion, Applicability::MaybeIncorrect);
true
},
);
err.emit();
}
fn suggest_introducing_lifetime(
&self,
err: &mut Diagnostic,
name: Option<&str>,
suggest: impl Fn(&mut Diagnostic, bool, Span, &str, String) -> bool,
) {
let mut suggest_note = true;
for rib in self.lifetime_ribs.iter().rev() {
let mut should_continue = true;
match rib.kind {
LifetimeRibKind::Generics { binder: _, span, kind } => {
if !span.can_be_used_for_suggestions() && suggest_note && let Some(name) = name {
suggest_note = false; // Avoid displaying the same help multiple times.
err.span_label(
span,
&format!(
"lifetime `{}` is missing in item created through this procedural macro",
name,
),
);
continue;
}
let higher_ranked = matches!(
kind,
LifetimeBinderKind::BareFnType
| LifetimeBinderKind::PolyTrait
| LifetimeBinderKind::WhereBound
);
let (span, sugg) = if span.is_empty() {
let sugg = format!(
"{}<{}>{}",
if higher_ranked { "for" } else { "" },
name.unwrap_or("'a"),
if higher_ranked { " " } else { "" },
);
(span, sugg)
} else {
let span =
self.r.session.source_map().span_through_char(span, '<').shrink_to_hi();
let sugg = format!("{}, ", name.unwrap_or("'a"));
(span, sugg)
};
if higher_ranked {
let message = format!(
"consider making the {} lifetime-generic with a new `{}` lifetime",
kind.descr(),
name.unwrap_or("'a"),
);
should_continue = suggest(err, true, span, &message, sugg);
err.note_once(
"for more information on higher-ranked polymorphism, visit \
https://doc.rust-lang.org/nomicon/hrtb.html",
);
} else if let Some(name) = name {
let message = format!("consider introducing lifetime `{}` here", name);
should_continue = suggest(err, false, span, &message, sugg);
} else {
let message = format!("consider introducing a named lifetime parameter");
should_continue = suggest(err, false, span, &message, sugg);
}
}
LifetimeRibKind::Item => break,
_ => {}
}
if !should_continue {
break;
}
}
}
pub(crate) fn emit_non_static_lt_in_const_generic_error(&self, lifetime_ref: &ast::Lifetime) {
struct_span_err!(
self.r.session,
lifetime_ref.ident.span,
E0771,
"use of non-static lifetime `{}` in const generic",
lifetime_ref.ident
)
.note(
"for more information, see issue #74052 \
<https://github.com/rust-lang/rust/issues/74052>",
)
.emit();
}
/// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics`.
/// This function will emit an error if `generic_const_exprs` is not enabled, the body identified by
/// `body_id` is an anonymous constant and `lifetime_ref` is non-static.
pub(crate) fn maybe_emit_forbidden_non_static_lifetime_error(
&self,
lifetime_ref: &ast::Lifetime,
) {
let feature_active = self.r.session.features_untracked().generic_const_exprs;
if !feature_active {
feature_err(
&self.r.session.parse_sess,
sym::generic_const_exprs,
lifetime_ref.ident.span,
"a non-static lifetime is not allowed in a `const`",
)
.emit();
}
}
pub(crate) fn report_missing_lifetime_specifiers(
&mut self,
lifetime_refs: Vec<MissingLifetime>,
function_param_lifetimes: Option<(Vec<MissingLifetime>, Vec<ElisionFnParameter>)>,
) -> ErrorGuaranteed {
let num_lifetimes: usize = lifetime_refs.iter().map(|lt| lt.count).sum();
let spans: Vec<_> = lifetime_refs.iter().map(|lt| lt.span).collect();
let mut err = struct_span_err!(
self.r.session,
spans,
E0106,
"missing lifetime specifier{}",
pluralize!(num_lifetimes)
);
self.add_missing_lifetime_specifiers_label(
&mut err,
lifetime_refs,
function_param_lifetimes,
);
err.emit()
}
fn add_missing_lifetime_specifiers_label(
&mut self,
err: &mut Diagnostic,
lifetime_refs: Vec<MissingLifetime>,
function_param_lifetimes: Option<(Vec<MissingLifetime>, Vec<ElisionFnParameter>)>,
) {
for &lt in &lifetime_refs {
err.span_label(
lt.span,
format!(
"expected {} lifetime parameter{}",
if lt.count == 1 { "named".to_string() } else { lt.count.to_string() },
pluralize!(lt.count),
),
);
}
let mut in_scope_lifetimes: Vec<_> = self
.lifetime_ribs
.iter()
.rev()
.take_while(|rib| !matches!(rib.kind, LifetimeRibKind::Item))
.flat_map(|rib| rib.bindings.iter())
.map(|(&ident, &res)| (ident, res))
.filter(|(ident, _)| ident.name != kw::UnderscoreLifetime)
.collect();
debug!(?in_scope_lifetimes);
debug!(?function_param_lifetimes);
if let Some((param_lifetimes, params)) = &function_param_lifetimes {
let elided_len = param_lifetimes.len();
let num_params = params.len();
let mut m = String::new();
for (i, info) in params.iter().enumerate() {
let ElisionFnParameter { ident, index, lifetime_count, span } = *info;
debug_assert_ne!(lifetime_count, 0);
err.span_label(span, "");
if i != 0 {
if i + 1 < num_params {
m.push_str(", ");
} else if num_params == 2 {
m.push_str(" or ");
} else {
m.push_str(", or ");
}
}
let help_name = if let Some(ident) = ident {
format!("`{}`", ident)
} else {
format!("argument {}", index + 1)
};
if lifetime_count == 1 {
m.push_str(&help_name[..])
} else {
m.push_str(&format!("one of {}'s {} lifetimes", help_name, lifetime_count)[..])
}
}
if num_params == 0 {
err.help(
"this function's return type contains a borrowed value, \
but there is no value for it to be borrowed from",
);
if in_scope_lifetimes.is_empty() {
in_scope_lifetimes = vec![(
Ident::with_dummy_span(kw::StaticLifetime),
(DUMMY_NODE_ID, LifetimeRes::Static),
)];
}
} else if elided_len == 0 {
err.help(
"this function's return type contains a borrowed value with \
an elided lifetime, but the lifetime cannot be derived from \
the arguments",
);
if in_scope_lifetimes.is_empty() {
in_scope_lifetimes = vec![(
Ident::with_dummy_span(kw::StaticLifetime),
(DUMMY_NODE_ID, LifetimeRes::Static),
)];
}
} else if num_params == 1 {
err.help(&format!(
"this function's return type contains a borrowed value, \
but the signature does not say which {} it is borrowed from",
m
));
} else {
err.help(&format!(
"this function's return type contains a borrowed value, \
but the signature does not say whether it is borrowed from {}",
m
));
}
}
let existing_name = match &in_scope_lifetimes[..] {
[] => Symbol::intern("'a"),
[(existing, _)] => existing.name,
_ => Symbol::intern("'lifetime"),
};
let mut spans_suggs: Vec<_> = Vec::new();
let build_sugg = |lt: MissingLifetime| match lt.kind {
MissingLifetimeKind::Underscore => {
debug_assert_eq!(lt.count, 1);
(lt.span, existing_name.to_string())
}
MissingLifetimeKind::Ampersand => {
debug_assert_eq!(lt.count, 1);
(lt.span.shrink_to_hi(), format!("{} ", existing_name))
}
MissingLifetimeKind::Comma => {
let sugg: String = std::iter::repeat([existing_name.as_str(), ", "])
.take(lt.count)
.flatten()
.collect();
(lt.span.shrink_to_hi(), sugg)
}
MissingLifetimeKind::Brackets => {
let sugg: String = std::iter::once("<")
.chain(
std::iter::repeat(existing_name.as_str()).take(lt.count).intersperse(", "),
)
.chain([">"])
.collect();
(lt.span.shrink_to_hi(), sugg)
}
};
for &lt in &lifetime_refs {
spans_suggs.push(build_sugg(lt));
}
debug!(?spans_suggs);
match in_scope_lifetimes.len() {
0 => {
if let Some((param_lifetimes, _)) = function_param_lifetimes {
for lt in param_lifetimes {
spans_suggs.push(build_sugg(lt))
}
}
self.suggest_introducing_lifetime(
err,
None,
|err, higher_ranked, span, message, intro_sugg| {
err.multipart_suggestion_verbose(
message,
std::iter::once((span, intro_sugg))
.chain(spans_suggs.iter().cloned())
.collect(),
Applicability::MaybeIncorrect,
);
higher_ranked
},
);
}
1 => {
err.multipart_suggestion_verbose(
&format!("consider using the `{}` lifetime", existing_name),
spans_suggs,
Applicability::MaybeIncorrect,
);
// Record as using the suggested resolution.
let (_, (_, res)) = in_scope_lifetimes[0];
for &lt in &lifetime_refs {
self.r.lifetimes_res_map.insert(lt.id, res);
}
}
_ => {
let lifetime_spans: Vec<_> =
in_scope_lifetimes.iter().map(|(ident, _)| ident.span).collect();
err.span_note(lifetime_spans, "these named lifetimes are available to use");
if spans_suggs.len() > 0 {
// This happens when we have `Foo<T>` where we point at the space before `T`,
// but this can be confusing so we give a suggestion with placeholders.
err.multipart_suggestion_verbose(
"consider using one of the available lifetimes here",
spans_suggs,
Applicability::HasPlaceholders,
);
}
}
}
}
}
/// Report lifetime/lifetime shadowing as an error.
pub fn signal_lifetime_shadowing(sess: &Session, orig: Ident, shadower: Ident) {
let mut err = struct_span_err!(
sess,
shadower.span,
E0496,
"lifetime name `{}` shadows a lifetime name that is already in scope",
orig.name,
);
err.span_label(orig.span, "first declared here");
err.span_label(shadower.span, format!("lifetime `{}` already in scope", orig.name));
err.emit();
}
/// Shadowing involving a label is only a warning for historical reasons.
//FIXME: make this a proper lint.
pub fn signal_label_shadowing(sess: &Session, orig: Span, shadower: Ident) {
let name = shadower.name;
let shadower = shadower.span;
let mut err = sess.struct_span_warn(
shadower,
&format!("label name `{}` shadows a label name that is already in scope", name),
);
err.span_label(orig, "first declared here");
err.span_label(shadower, format!("label `{}` already in scope", name));
err.emit();
}
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