src/librustc_session/parse.rs

   1 //! Contains `ParseSess` which holds state living beyond what one `Parser` might.
   2 //! It also serves as an input to the parser itself.
   3
   4 use crate::lint::{BufferedEarlyLint, BuiltinLintDiagnostics, Lint, LintId};
   5 use crate::node_id::NodeId;
   6
   7 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   8 use rustc_data_structures::sync::{Lock, Lrc, Once};
   9 use rustc_error_codes::E0658;
  10 use rustc_errors::{emitter::SilentEmitter, ColorConfig, Handler};
  11 use rustc_errors::{error_code, Applicability, DiagnosticBuilder};
  12 use rustc_feature::{find_feature_issue, GateIssue, UnstableFeatures};
  13 use rustc_span::edition::Edition;
  14 use rustc_span::hygiene::ExpnId;
  15 use rustc_span::source_map::{FilePathMapping, SourceMap};
  16 use rustc_span::{MultiSpan, Span, Symbol};
  17
  18 use std::path::PathBuf;
  19 use std::str;
  20
  21 /// The set of keys (and, optionally, values) that define the compilation
  22 /// environment of the crate, used to drive conditional compilation.
  23 pub type CrateConfig = FxHashSet<(Symbol, Option<Symbol>)>;
  24
  25 /// Collected spans during parsing for places where a certain feature was
  26 /// used and should be feature gated accordingly in `check_crate`.
  27 #[derive(Default)]
  28 pub struct GatedSpans {
  29     pub spans: Lock<FxHashMap<Symbol, Vec<Span>>>,
  30 }
  31
  32 impl GatedSpans {
  33     /// Feature gate the given `span` under the given `feature`
  34     /// which is same `Symbol` used in `active.rs`.
  35     pub fn gate(&self, feature: Symbol, span: Span) {
  36         self.spans.borrow_mut().entry(feature).or_default().push(span);
  37     }
  38
  39     /// Ungate the last span under the given `feature`.
  40     /// Panics if the given `span` wasn't the last one.
  41     ///
  42     /// Using this is discouraged unless you have a really good reason to.
  43     pub fn ungate_last(&self, feature: Symbol, span: Span) {
  44         let removed_span = self.spans.borrow_mut().entry(feature).or_default().pop().unwrap();
  45         debug_assert_eq!(span, removed_span);
  46     }
  47
  48     /// Is the provided `feature` gate ungated currently?
  49     ///
  50     /// Using this is discouraged unless you have a really good reason to.
  51     pub fn is_ungated(&self, feature: Symbol) -> bool {
  52         self.spans.borrow().get(&feature).map_or(true, |spans| spans.is_empty())
  53     }
  54
  55     /// Prepend the given set of `spans` onto the set in `self`.
  56     pub fn merge(&self, mut spans: FxHashMap<Symbol, Vec<Span>>) {
  57         let mut inner = self.spans.borrow_mut();
  58         for (gate, mut gate_spans) in inner.drain() {
  59             spans.entry(gate).or_default().append(&mut gate_spans);
  60         }
  61         *inner = spans;
  62     }
  63 }
  64
  65 /// Construct a diagnostic for a language feature error due to the given `span`.
  66 /// The `feature`'s `Symbol` is the one you used in `active.rs` and `rustc_span::symbols`.
  67 pub fn feature_err<'a>(
  68     sess: &'a ParseSess,
  69     feature: Symbol,
  70     span: impl Into<MultiSpan>,
  71     explain: &str,
  72 ) -> DiagnosticBuilder<'a> {
  73     feature_err_issue(sess, feature, span, GateIssue::Language, explain)
  74 }
  75
  76 /// Construct a diagnostic for a feature gate error.
  77 ///
  78 /// This variant allows you to control whether it is a library or language feature.
  79 /// Almost always, you want to use this for a language feature. If so, prefer `feature_err`.
  80 pub fn feature_err_issue<'a>(
  81     sess: &'a ParseSess,
  82     feature: Symbol,
  83     span: impl Into<MultiSpan>,
  84     issue: GateIssue,
  85     explain: &str,
  86 ) -> DiagnosticBuilder<'a> {
  87     let mut err = sess.span_diagnostic.struct_span_err_with_code(span, explain, error_code!(E0658));
  88
  89     if let Some(n) = find_feature_issue(feature, issue) {
  90         err.note(&format!(
  91             "for more information, see https://github.com/rust-lang/rust/issues/{}",
  92             n,
  93         ));
  94     }
  95
  96     // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
  97     if sess.unstable_features.is_nightly_build() {
  98         err.help(&format!("add `#![feature({})]` to the crate attributes to enable", feature));
  99     }
 100
 101     err
 102 }
 103
 104 /// Info about a parsing session.
 105 pub struct ParseSess {
 106     pub span_diagnostic: Handler,
 107     pub unstable_features: UnstableFeatures,
 108     pub config: CrateConfig,
 109     pub edition: Edition,
 110     pub missing_fragment_specifiers: Lock<FxHashSet<Span>>,
 111     /// Places where raw identifiers were used. This is used for feature-gating raw identifiers.
 112     pub raw_identifier_spans: Lock<Vec<Span>>,
 113     /// Used to determine and report recursive module inclusions.
 114     pub included_mod_stack: Lock<Vec<PathBuf>>,
 115     source_map: Lrc<SourceMap>,
 116     pub buffered_lints: Lock<Vec<BufferedEarlyLint>>,
 117     /// Contains the spans of block expressions that could have been incomplete based on the
 118     /// operation token that followed it, but that the parser cannot identify without further
 119     /// analysis.
 120     pub ambiguous_block_expr_parse: Lock<FxHashMap<Span, Span>>,
 121     pub injected_crate_name: Once<Symbol>,
 122     pub gated_spans: GatedSpans,
 123     /// The parser has reached `Eof` due to an unclosed brace. Used to silence unnecessary errors.
 124     pub reached_eof: Lock<bool>,
 125 }
 126
 127 impl ParseSess {
 128     pub fn new(file_path_mapping: FilePathMapping) -> Self {
 129         let cm = Lrc::new(SourceMap::new(file_path_mapping));
 130         let handler = Handler::with_tty_emitter(ColorConfig::Auto, true, None, Some(cm.clone()));
 131         ParseSess::with_span_handler(handler, cm)
 132     }
 133
 134     pub fn with_span_handler(handler: Handler, source_map: Lrc<SourceMap>) -> Self {
 135         Self {
 136             span_diagnostic: handler,
 137             unstable_features: UnstableFeatures::from_environment(),
 138             config: FxHashSet::default(),
 139             edition: ExpnId::root().expn_data().edition,
 140             missing_fragment_specifiers: Lock::new(FxHashSet::default()),
 141             raw_identifier_spans: Lock::new(Vec::new()),
 142             included_mod_stack: Lock::new(vec![]),
 143             source_map,
 144             buffered_lints: Lock::new(vec![]),
 145             ambiguous_block_expr_parse: Lock::new(FxHashMap::default()),
 146             injected_crate_name: Once::new(),
 147             gated_spans: GatedSpans::default(),
 148             reached_eof: Lock::new(false),
 149         }
 150     }
 151
 152     pub fn with_silent_emitter() -> Self {
 153         let cm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
 154         let handler = Handler::with_emitter(false, None, Box::new(SilentEmitter));
 155         ParseSess::with_span_handler(handler, cm)
 156     }
 157
 158     #[inline]
 159     pub fn source_map(&self) -> &SourceMap {
 160         &self.source_map
 161     }
 162
 163     pub fn buffer_lint(
 164         &self,
 165         lint: &'static Lint,
 166         span: impl Into<MultiSpan>,
 167         node_id: NodeId,
 168         msg: &str,
 169     ) {
 170         self.buffered_lints.with_lock(|buffered_lints| {
 171             buffered_lints.push(BufferedEarlyLint {
 172                 span: span.into(),
 173                 node_id,
 174                 msg: msg.into(),
 175                 lint_id: LintId::of(lint),
 176                 diagnostic: BuiltinLintDiagnostics::Normal,
 177             });
 178         });
 179     }
 180
 181     /// Extend an error with a suggestion to wrap an expression with parentheses to allow the
 182     /// parser to continue parsing the following operation as part of the same expression.
 183     pub fn expr_parentheses_needed(
 184         &self,
 185         err: &mut DiagnosticBuilder<'_>,
 186         span: Span,
 187         alt_snippet: Option<String>,
 188     ) {
 189         if let Some(snippet) = self.source_map().span_to_snippet(span).ok().or(alt_snippet) {
 190             err.span_suggestion(
 191                 span,
 192                 "parentheses are required to parse this as an expression",
 193                 format!("({})", snippet),
 194                 Applicability::MachineApplicable,
 195             );
 196         }
 197     }
 198 }