1 files changed, 239 insertions, 0 deletions
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
new file mode 100644
index 00000000000..6f10d0c4b89
--- /dev/null
+++ b/compiler/rustc_session/src/parse.rs
@@ -0,0 +1,239 @@
+//! Contains `ParseSess` which holds state living beyond what one `Parser` might.
+//! It also serves as an input to the parser itself.
+
+use crate::lint::{BufferedEarlyLint, BuiltinLintDiagnostics, Lint, LintId};
+use rustc_ast::node_id::NodeId;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::sync::{Lock, Lrc, OnceCell};
+use rustc_errors::{emitter::SilentEmitter, ColorConfig, Handler};
+use rustc_errors::{error_code, Applicability, DiagnosticBuilder};
+use rustc_feature::{find_feature_issue, GateIssue, UnstableFeatures};
+use rustc_span::edition::Edition;
+use rustc_span::hygiene::ExpnId;
+use rustc_span::source_map::{FilePathMapping, SourceMap};
+use rustc_span::{MultiSpan, Span, Symbol};
+
+use std::path::PathBuf;
+use std::str;
+
+/// The set of keys (and, optionally, values) that define the compilation
+/// environment of the crate, used to drive conditional compilation.
+pub type CrateConfig = FxHashSet<(Symbol, Option<Symbol>)>;
+
+/// Collected spans during parsing for places where a certain feature was
+/// used and should be feature gated accordingly in `check_crate`.
+#[derive(Default)]
+pub struct GatedSpans {
+    pub spans: Lock<FxHashMap<Symbol, Vec<Span>>>,
+}
+
+impl GatedSpans {
+    /// Feature gate the given `span` under the given `feature`
+    /// which is same `Symbol` used in `active.rs`.
+    pub fn gate(&self, feature: Symbol, span: Span) {
+        self.spans.borrow_mut().entry(feature).or_default().push(span);
+    }
+
+    /// Ungate the last span under the given `feature`.
+    /// Panics if the given `span` wasn't the last one.
+    ///
+    /// Using this is discouraged unless you have a really good reason to.
+    pub fn ungate_last(&self, feature: Symbol, span: Span) {
+        let removed_span = self.spans.borrow_mut().entry(feature).or_default().pop().unwrap();
+        debug_assert_eq!(span, removed_span);
+    }
+
+    /// Is the provided `feature` gate ungated currently?
+    ///
+    /// Using this is discouraged unless you have a really good reason to.
+    pub fn is_ungated(&self, feature: Symbol) -> bool {
+        self.spans.borrow().get(&feature).map_or(true, |spans| spans.is_empty())
+    }
+
+    /// Prepend the given set of `spans` onto the set in `self`.
+    pub fn merge(&self, mut spans: FxHashMap<Symbol, Vec<Span>>) {
+        let mut inner = self.spans.borrow_mut();
+        for (gate, mut gate_spans) in inner.drain() {
+            spans.entry(gate).or_default().append(&mut gate_spans);
+        }
+        *inner = spans;
+    }
+}
+
+#[derive(Default)]
+pub struct SymbolGallery {
+    /// All symbols occurred and their first occurrence span.
+    pub symbols: Lock<FxHashMap<Symbol, Span>>,
+}
+
+impl SymbolGallery {
+    /// Insert a symbol and its span into symbol gallery.
+    /// If the symbol has occurred before, ignore the new occurance.
+    pub fn insert(&self, symbol: Symbol, span: Span) {
+        self.symbols.lock().entry(symbol).or_insert(span);
+    }
+}
+
+/// Construct a diagnostic for a language feature error due to the given `span`.
+/// The `feature`'s `Symbol` is the one you used in `active.rs` and `rustc_span::symbols`.
+pub fn feature_err<'a>(
+    sess: &'a ParseSess,
+    feature: Symbol,
+    span: impl Into<MultiSpan>,
+    explain: &str,
+) -> DiagnosticBuilder<'a> {
+    feature_err_issue(sess, feature, span, GateIssue::Language, explain)
+}
+
+/// Construct a diagnostic for a feature gate error.
+///
+/// This variant allows you to control whether it is a library or language feature.
+/// Almost always, you want to use this for a language feature. If so, prefer `feature_err`.
+pub fn feature_err_issue<'a>(
+    sess: &'a ParseSess,
+    feature: Symbol,
+    span: impl Into<MultiSpan>,
+    issue: GateIssue,
+    explain: &str,
+) -> DiagnosticBuilder<'a> {
+    let mut err = sess.span_diagnostic.struct_span_err_with_code(span, explain, error_code!(E0658));
+
+    if let Some(n) = find_feature_issue(feature, issue) {
+        err.note(&format!(
+            "see issue #{} <https://github.com/rust-lang/rust/issues/{}> for more information",
+            n, n,
+        ));
+    }
+
+    // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
+    if sess.unstable_features.is_nightly_build() {
+        err.help(&format!("add `#![feature({})]` to the crate attributes to enable", feature));
+    }
+
+    err
+}
+
+/// Info about a parsing session.
+pub struct ParseSess {
+    pub span_diagnostic: Handler,
+    pub unstable_features: UnstableFeatures,
+    pub config: CrateConfig,
+    pub edition: Edition,
+    /// Places where raw identifiers were used. This is used for feature-gating raw identifiers.
+    pub raw_identifier_spans: Lock<Vec<Span>>,
+    /// Used to determine and report recursive module inclusions.
+    pub included_mod_stack: Lock<Vec<PathBuf>>,
+    source_map: Lrc<SourceMap>,
+    pub buffered_lints: Lock<Vec<BufferedEarlyLint>>,
+    /// Contains the spans of block expressions that could have been incomplete based on the
+    /// operation token that followed it, but that the parser cannot identify without further
+    /// analysis.
+    pub ambiguous_block_expr_parse: Lock<FxHashMap<Span, Span>>,
+    pub injected_crate_name: OnceCell<Symbol>,
+    pub gated_spans: GatedSpans,
+    pub symbol_gallery: SymbolGallery,
+    /// The parser has reached `Eof` due to an unclosed brace. Used to silence unnecessary errors.
+    pub reached_eof: Lock<bool>,
+    /// Environment variables accessed during the build and their values when they exist.
+    pub env_depinfo: Lock<FxHashSet<(Symbol, Option<Symbol>)>>,
+    /// All the type ascriptions expressions that have had a suggestion for likely path typo.
+    pub type_ascription_path_suggestions: Lock<FxHashSet<Span>>,
+}
+
+impl ParseSess {
+    pub fn new(file_path_mapping: FilePathMapping) -> Self {
+        let sm = Lrc::new(SourceMap::new(file_path_mapping));
+        let handler = Handler::with_tty_emitter(ColorConfig::Auto, true, None, Some(sm.clone()));
+        ParseSess::with_span_handler(handler, sm)
+    }
+
+    pub fn with_span_handler(handler: Handler, source_map: Lrc<SourceMap>) -> Self {
+        Self {
+            span_diagnostic: handler,
+            unstable_features: UnstableFeatures::from_environment(),
+            config: FxHashSet::default(),
+            edition: ExpnId::root().expn_data().edition,
+            raw_identifier_spans: Lock::new(Vec::new()),
+            included_mod_stack: Lock::new(vec![]),
+            source_map,
+            buffered_lints: Lock::new(vec![]),
+            ambiguous_block_expr_parse: Lock::new(FxHashMap::default()),
+            injected_crate_name: OnceCell::new(),
+            gated_spans: GatedSpans::default(),
+            symbol_gallery: SymbolGallery::default(),
+            reached_eof: Lock::new(false),
+            env_depinfo: Default::default(),
+            type_ascription_path_suggestions: Default::default(),
+        }
+    }
+
+    pub fn with_silent_emitter() -> Self {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let handler = Handler::with_emitter(false, None, Box::new(SilentEmitter));
+        ParseSess::with_span_handler(handler, sm)
+    }
+
+    #[inline]
+    pub fn source_map(&self) -> &SourceMap {
+        &self.source_map
+    }
+
+    pub fn clone_source_map(&self) -> Lrc<SourceMap> {
+        self.source_map.clone()
+    }
+
+    pub fn buffer_lint(
+        &self,
+        lint: &'static Lint,
+        span: impl Into<MultiSpan>,
+        node_id: NodeId,
+        msg: &str,
+    ) {
+        self.buffered_lints.with_lock(|buffered_lints| {
+            buffered_lints.push(BufferedEarlyLint {
+                span: span.into(),
+                node_id,
+                msg: msg.into(),
+                lint_id: LintId::of(lint),
+                diagnostic: BuiltinLintDiagnostics::Normal,
+            });
+        });
+    }
+
+    pub fn buffer_lint_with_diagnostic(
+        &self,
+        lint: &'static Lint,
+        span: impl Into<MultiSpan>,
+        node_id: NodeId,
+        msg: &str,
+        diagnostic: BuiltinLintDiagnostics,
+    ) {
+        self.buffered_lints.with_lock(|buffered_lints| {
+            buffered_lints.push(BufferedEarlyLint {
+                span: span.into(),
+                node_id,
+                msg: msg.into(),
+                lint_id: LintId::of(lint),
+                diagnostic,
+            });
+        });
+    }
+
+    /// Extend an error with a suggestion to wrap an expression with parentheses to allow the
+    /// parser to continue parsing the following operation as part of the same expression.
+    pub fn expr_parentheses_needed(
+        &self,
+        err: &mut DiagnosticBuilder<'_>,
+        span: Span,
+        alt_snippet: Option<String>,
+    ) {
+        if let Some(snippet) = self.source_map().span_to_snippet(span).ok().or(alt_snippet) {
+            err.span_suggestion(
+                span,
+                "parentheses are required to parse this as an expression",
+                format!("({})", snippet),
+                Applicability::MachineApplicable,
+            );
+        }
+    }
+}