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Auto merge of #93368 - eddyb:diagbld-guarantee, r=estebank

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rustc_errors: let `DiagnosticBuilder::emit` return a "guarantee of emission".

That is, `DiagnosticBuilder` is now generic over the return type of `.emit()`, so we'll now have:
* `DiagnosticBuilder<ErrorReported>` for error (incl. fatal/bug) diagnostics
  * can only be created via a `const L: Level`-generic constructor, that limits allowed variants via a `where` clause, so not even `rustc_errors` can accidentally bypass this limitation
  * asserts `diagnostic.is_error()` on emission, just in case the construction restriction was bypassed (e.g. by replacing the whole `Diagnostic` inside `DiagnosticBuilder`)
  * `.emit()` returns `ErrorReported`, as a "proof" token that `.emit()` was called
    (though note that this isn't a real guarantee until after completing the work on
     #69426)
* `DiagnosticBuilder<()>` for everything else (warnings, notes, etc.)
  * can also be obtained from other `DiagnosticBuilder`s by calling `.forget_guarantee()`

This PR is a companion to other ongoing work, namely:
* #69426
  and it's ongoing implementation:
  #93222
  the API changes in this PR are needed to get statically-checked "only errors produce `ErrorReported` from `.emit()`", but doesn't itself provide any really strong guarantees without those other `ErrorReported` changes
* #93244
  would make the choices of API changes (esp. naming) in this PR fit better overall

In order to be able to let `.emit()` return anything trustable, several changes had to be made:
* `Diagnostic`'s `level` field is now private to `rustc_errors`, to disallow arbitrary "downgrade"s from "some kind of error" to "warning" (or anything else that doesn't cause compilation to fail)
  * it's still possible to replace the whole `Diagnostic` inside the `DiagnosticBuilder`, sadly, that's harder to fix, but it's unlikely enough that we can paper over it with asserts on `.emit()`
* `.cancel()` now consumes `DiagnosticBuilder`, preventing `.emit()` calls on a cancelled diagnostic
  * it's also now done internally, through `DiagnosticBuilder`-private state, instead of having a `Level::Cancelled` variant that can be read (or worse, written) by the user
  * this removes a hazard of calling `.cancel()` on an error then continuing to attach details to it, and even expect to be able to `.emit()` it
  * warnings were switched to *only* `can_emit_warnings` on emission (instead of pre-cancelling early)
  * `struct_dummy` was removed (as it relied on a pre-`Cancelled` `Diagnostic`)
* since `.emit()` doesn't consume the `DiagnosticBuilder` <sub>(I tried and gave up, it's much more work than this PR)</sub>,
  we have to make `.emit()` idempotent wrt the guarantees it returns
  * thankfully, `err.emit(); err.emit();` can return `ErrorReported` both times, as the second `.emit()` call has no side-effects *only* because the first one did do the appropriate emission
* `&mut Diagnostic` is now used in a lot of function signatures, which used to take `&mut DiagnosticBuilder` (in the interest of not having to make those functions generic)
  * the APIs were already mostly identical, allowing for low-effort porting to this new setup
  * only some of the suggestion methods needed some rework, to have the extra `DiagnosticBuilder` functionality on the `Diagnostic` methods themselves (that change is also present in #93259)
  * `.emit()`/`.cancel()` aren't available, but IMO calling them from an "error decorator/annotator" function isn't a good practice, and can lead to strange behavior (from the caller's perspective)
  * `.downgrade_to_delayed_bug()` was added, letting you convert any `.is_error()` diagnostic into a `delay_span_bug` one (which works because in both cases the guarantees available are the same)

This PR should ideally be reviewed commit-by-commit, since there is a lot of fallout in each.

r? `@estebank` cc `@Manishearth` `@nikomatsakis` `@mark-i-m`
This commit is contained in:
bors 2022-02-25 00:46:04 +00:00
commit d4de1f230c
134 changed files with 1497 additions and 1143 deletions
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5
compiler/rustc_resolve/src/build_reduced_graph.rs
View file

@ -1070,8 +1070,9 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
.emit();
}
}
let ill_formed =
|span| struct_span_err!(self.r.session, span, E0466, "bad macro import").emit();
let ill_formed = |span| {
struct_span_err!(self.r.session, span, E0466, "bad macro import").emit();
};
match attr.meta() {
Some(meta) => match meta.kind {
MetaItemKind::Word => {

15
compiler/rustc_resolve/src/diagnostics.rs
View file

@ -3,7 +3,7 @@ use std::ptr;
use rustc_ast::{self as ast, Path};
use rustc_ast_pretty::pprust;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
use rustc_errors::{struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorReported};
use rustc_feature::BUILTIN_ATTRIBUTES;
use rustc_hir::def::Namespace::{self, *};
use rustc_hir::def::{self, CtorKind, CtorOf, DefKind, NonMacroAttrKind};
@ -110,7 +110,7 @@ impl<'a> Resolver<'a> {
&self,
span: Span,
resolution_error: ResolutionError<'_>,
) -> DiagnosticBuilder<'_> {
) -> DiagnosticBuilder<'_, ErrorReported> {
match resolution_error {
ResolutionError::GenericParamsFromOuterFunction(outer_res, has_generic_params) => {
let mut err = struct_span_err!(
@ -624,7 +624,10 @@ impl<'a> Resolver<'a> {
}
}
crate fn report_vis_error(&self, vis_resolution_error: VisResolutionError<'_>) {
crate fn report_vis_error(
&self,
vis_resolution_error: VisResolutionError<'_>,
) -> ErrorReported {
match vis_resolution_error {
VisResolutionError::Relative2018(span, path) => {
let mut err = self.session.struct_span_err(
@ -1031,7 +1034,7 @@ impl<'a> Resolver<'a> {
crate fn unresolved_macro_suggestions(
&mut self,
err: &mut DiagnosticBuilder<'a>,
err: &mut Diagnostic,
macro_kind: MacroKind,
parent_scope: &ParentScope<'a>,
ident: Ident,
@ -1120,7 +1123,7 @@ impl<'a> Resolver<'a> {
crate fn add_typo_suggestion(
&self,
err: &mut DiagnosticBuilder<'_>,
err: &mut Diagnostic,
suggestion: Option<TypoSuggestion>,
span: Span,
) -> bool {
@ -1817,7 +1820,7 @@ fn find_span_immediately_after_crate_name(
crate fn show_candidates(
definitions: &rustc_hir::definitions::Definitions,
session: &Session,
err: &mut DiagnosticBuilder<'_>,
err: &mut Diagnostic,
// This is `None` if all placement locations are inside expansions
use_placement_span: Option<Span>,
candidates: &[ImportSuggestion],

4
compiler/rustc_resolve/src/late.rs
View file

@ -2001,13 +2001,11 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
// into a single one.
let mut parent_err = this.r.into_struct_error(parent_err.span, parent_err.node);
parent_err.cancel();
err.message = take(&mut parent_err.message);
err.code = take(&mut parent_err.code);
err.children = take(&mut parent_err.children);
drop(parent_err);
parent_err.cancel();
let def_id = this.parent_scope.module.nearest_parent_mod();

43
compiler/rustc_resolve/src/late/diagnostics.rs
View file

@ -12,7 +12,9 @@ use rustc_ast::{
};
use rustc_ast_pretty::pprust::path_segment_to_string;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
use rustc_errors::{
pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorReported,
};
use rustc_hir as hir;
use rustc_hir::def::Namespace::{self, *};
use rustc_hir::def::{self, CtorKind, CtorOf, DefKind};
@ -133,7 +135,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
span: Span,
source: PathSource<'_>,
res: Option<Res>,
) -> (DiagnosticBuilder<'a>, Vec<ImportSuggestion>) {
) -> (DiagnosticBuilder<'a, ErrorReported>, 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);
@ -606,11 +608,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
(err, candidates)
}
fn detect_assoct_type_constraint_meant_as_path(
&self,
base_span: Span,
err: &mut DiagnosticBuilder<'_>,
) {
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 {
@ -675,11 +673,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
}
/// 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 DiagnosticBuilder<'_>,
) -> bool {
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 {
@ -875,7 +869,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
/// Returns `true` if able to provide context-dependent help.
fn smart_resolve_context_dependent_help(
&mut self,
err: &mut DiagnosticBuilder<'a>,
err: &mut Diagnostic,
span: Span,
source: PathSource<'_>,
res: Res,
@ -885,7 +879,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
let ns = source.namespace();
let is_expected = &|res| source.is_expected(res);
let path_sep = |err: &mut DiagnosticBuilder<'_>, expr: &Expr| match expr.kind {
let path_sep = |err: &mut Diagnostic, expr: &Expr| match expr.kind {
ExprKind::Field(_, ident) => {
err.span_suggestion(
expr.span,
@ -908,7 +902,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
_ => false,
};
let find_span = |source: &PathSource<'_>, err: &mut DiagnosticBuilder<'_>| {
let find_span = |source: &PathSource<'_>, err: &mut Diagnostic| {
match source {
PathSource::Expr(Some(Expr { span, kind: ExprKind::Call(_, _), .. }))
| PathSource::TupleStruct(span, _) => {
@ -1066,7 +1060,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
})
.unwrap_or(false)
{
err.delay_as_bug();
err.downgrade_to_delayed_bug();
// We already suggested changing `:` into `::` during parsing.
return false;
}
@ -1435,7 +1429,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
start.to(sm.next_point(start))
}
fn type_ascription_suggestion(&self, err: &mut DiagnosticBuilder<'_>, base_span: Span) -> bool {
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() {
@ -1472,7 +1466,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
.borrow_mut()
.insert(colon_sp)
{
err.delay_as_bug();
err.downgrade_to_delayed_bug();
}
}
if let Ok(base_snippet) = base_snippet {
@ -1577,7 +1571,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
/// Adds a suggestion for using an enum's variant when an enum is used instead.
fn suggest_using_enum_variant(
&mut self,
err: &mut DiagnosticBuilder<'a>,
err: &mut Diagnostic,
source: PathSource<'_>,
def_id: DefId,
span: Span,
@ -1825,7 +1819,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
&self,
spans: Vec<Span>,
count: usize,
) -> DiagnosticBuilder<'tcx> {
) -> DiagnosticBuilder<'tcx, ErrorReported> {
struct_span_err!(
self.tcx.sess,
spans,
@ -1910,7 +1904,8 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
/// Returns whether to add `'static` lifetime to the suggested lifetime list.
crate fn report_elision_failure(
&mut self,
db: &mut DiagnosticBuilder<'_>,
// FIXME(eddyb) rename this since it's no longer a `DiagnosticBuilder`.
db: &mut Diagnostic,
params: &[ElisionFailureInfo],
) -> bool {
let mut m = String::new();
@ -2059,7 +2054,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
crate fn add_missing_lifetime_specifiers_label(
&self,
err: &mut DiagnosticBuilder<'_>,
err: &mut Diagnostic,
mut spans_with_counts: Vec<(Span, usize)>,
lifetime_names: &FxHashSet<Symbol>,
lifetime_spans: Vec<Span>,
@ -2090,7 +2085,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
}
let suggest_existing =
|err: &mut DiagnosticBuilder<'_>,
|err: &mut Diagnostic,
name: &str,
formatters: Vec<Option<Box<dyn Fn(&str) -> String>>>| {
if let Some(MissingLifetimeSpot::HigherRanked { span: for_span, span_type }) =
@ -2174,7 +2169,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
Applicability::MaybeIncorrect,
);
};
let suggest_new = |err: &mut DiagnosticBuilder<'_>, suggs: Vec<Option<String>>| {
let suggest_new = |err: &mut Diagnostic, suggs: Vec<Option<String>>| {
for missing in self.missing_named_lifetime_spots.iter().rev() {
let mut introduce_suggestion = vec![];
let msg;

5
compiler/rustc_resolve/src/late/lifetimes.rs
View file

@ -9,7 +9,7 @@
use crate::late::diagnostics::{ForLifetimeSpanType, MissingLifetimeSpot};
use rustc_ast::walk_list;
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
use rustc_errors::{struct_span_err, Applicability, Diagnostic};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{DefIdMap, LocalDefId};
@ -1572,6 +1572,7 @@ fn signal_shadowing_problem(tcx: TyCtxt<'_>, name: Symbol, orig: Original, shado
name,
orig.kind.desc()
)
.forget_guarantee()
} else {
// shadowing involving a label is only a warning, due to issues with
// labels and lifetimes not being macro-hygienic.
@ -1873,7 +1874,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
// or from `fn rah<'a>(T<'a>)` to `fn rah(T<'_>)`
fn suggest_eliding_single_use_lifetime(
&self,
err: &mut DiagnosticBuilder<'_>,
err: &mut Diagnostic,
def_id: DefId,
lifetime: &hir::Lifetime,
) {

8
compiler/rustc_resolve/src/lib.rs
View file

@ -40,7 +40,7 @@ use rustc_ast_pretty::pprust;
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
use rustc_data_structures::intern::Interned;
use rustc_data_structures::sync::Lrc;
use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
use rustc_errors::{struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorReported};
use rustc_expand::base::{DeriveResolutions, SyntaxExtension, SyntaxExtensionKind};
use rustc_hir::def::Namespace::*;
use rustc_hir::def::{self, CtorOf, DefKind, NonMacroAttrKind, PartialRes};
@ -713,7 +713,7 @@ struct PrivacyError<'a> {
}
struct UseError<'a> {
err: DiagnosticBuilder<'a>,
err: DiagnosticBuilder<'a, ErrorReported>,
/// Candidates which user could `use` to access the missing type.
candidates: Vec<ImportSuggestion>,
/// The `DefId` of the module to place the use-statements in.
@ -3173,7 +3173,7 @@ impl<'a> Resolver<'a> {
/// ```
fn add_suggestion_for_rename_of_use(
&self,
err: &mut DiagnosticBuilder<'_>,
err: &mut Diagnostic,
name: Symbol,
import: &Import<'_>,
binding_span: Span,
@ -3252,7 +3252,7 @@ impl<'a> Resolver<'a> {
/// as characters expected by span manipulations won't be present.
fn add_suggestion_for_duplicate_nested_use(
&self,
err: &mut DiagnosticBuilder<'_>,
err: &mut Diagnostic,
import: &Import<'_>,
binding_span: Span,
) {