1 files changed, 291 insertions, 0 deletions
diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
new file mode 100644
index 000000000..8c087c65c
--- /dev/null
+++ b/compiler/rustc_parse/src/lib.rs
@@ -0,0 +1,291 @@
+//! The main parser interface.
+
+#![feature(array_windows)]
+#![feature(box_patterns)]
+#![feature(if_let_guard)]
+#![feature(let_chains)]
+#![feature(let_else)]
+#![feature(never_type)]
+#![feature(rustc_attrs)]
+#![recursion_limit = "256"]
+
+#[macro_use]
+extern crate tracing;
+
+use rustc_ast as ast;
+use rustc_ast::token;
+use rustc_ast::tokenstream::TokenStream;
+use rustc_ast::Attribute;
+use rustc_ast::{AttrItem, MetaItem};
+use rustc_ast_pretty::pprust;
+use rustc_data_structures::sync::Lrc;
+use rustc_errors::{Applicability, Diagnostic, FatalError, Level, PResult};
+use rustc_session::parse::ParseSess;
+use rustc_span::{FileName, SourceFile, Span};
+
+use std::path::Path;
+
+pub const MACRO_ARGUMENTS: Option<&str> = Some("macro arguments");
+
+#[macro_use]
+pub mod parser;
+use parser::{emit_unclosed_delims, make_unclosed_delims_error, Parser};
+pub mod lexer;
+pub mod validate_attr;
+
+// A bunch of utility functions of the form `parse_<thing>_from_<source>`
+// where <thing> includes crate, expr, item, stmt, tts, and one that
+// uses a HOF to parse anything, and <source> includes file and
+// `source_str`.
+
+/// A variant of 'panictry!' that works on a Vec<Diagnostic> instead of a single DiagnosticBuilder.
+macro_rules! panictry_buffer {
+    ($handler:expr, $e:expr) => {{
+        use rustc_errors::FatalError;
+        use std::result::Result::{Err, Ok};
+        match $e {
+            Ok(e) => e,
+            Err(errs) => {
+                for mut e in errs {
+                    $handler.emit_diagnostic(&mut e);
+                }
+                FatalError.raise()
+            }
+        }
+    }};
+}
+
+pub fn parse_crate_from_file<'a>(input: &Path, sess: &'a ParseSess) -> PResult<'a, ast::Crate> {
+    let mut parser = new_parser_from_file(sess, input, None);
+    parser.parse_crate_mod()
+}
+
+pub fn parse_crate_attrs_from_file<'a>(
+    input: &Path,
+    sess: &'a ParseSess,
+) -> PResult<'a, Vec<ast::Attribute>> {
+    let mut parser = new_parser_from_file(sess, input, None);
+    parser.parse_inner_attributes()
+}
+
+pub fn parse_crate_from_source_str(
+    name: FileName,
+    source: String,
+    sess: &ParseSess,
+) -> PResult<'_, ast::Crate> {
+    new_parser_from_source_str(sess, name, source).parse_crate_mod()
+}
+
+pub fn parse_crate_attrs_from_source_str(
+    name: FileName,
+    source: String,
+    sess: &ParseSess,
+) -> PResult<'_, Vec<ast::Attribute>> {
+    new_parser_from_source_str(sess, name, source).parse_inner_attributes()
+}
+
+pub fn parse_stream_from_source_str(
+    name: FileName,
+    source: String,
+    sess: &ParseSess,
+    override_span: Option<Span>,
+) -> TokenStream {
+    let (stream, mut errors) =
+        source_file_to_stream(sess, sess.source_map().new_source_file(name, source), override_span);
+    emit_unclosed_delims(&mut errors, &sess);
+    stream
+}
+
+/// Creates a new parser from a source string.
+pub fn new_parser_from_source_str(sess: &ParseSess, name: FileName, source: String) -> Parser<'_> {
+    panictry_buffer!(&sess.span_diagnostic, maybe_new_parser_from_source_str(sess, name, source))
+}
+
+/// Creates a new parser from a source string. Returns any buffered errors from lexing the initial
+/// token stream.
+pub fn maybe_new_parser_from_source_str(
+    sess: &ParseSess,
+    name: FileName,
+    source: String,
+) -> Result<Parser<'_>, Vec<Diagnostic>> {
+    maybe_source_file_to_parser(sess, sess.source_map().new_source_file(name, source))
+}
+
+/// Creates a new parser, handling errors as appropriate if the file doesn't exist.
+/// If a span is given, that is used on an error as the source of the problem.
+pub fn new_parser_from_file<'a>(sess: &'a ParseSess, path: &Path, sp: Option<Span>) -> Parser<'a> {
+    source_file_to_parser(sess, file_to_source_file(sess, path, sp))
+}
+
+/// Given a session and a `source_file`, returns a parser.
+fn source_file_to_parser(sess: &ParseSess, source_file: Lrc<SourceFile>) -> Parser<'_> {
+    panictry_buffer!(&sess.span_diagnostic, maybe_source_file_to_parser(sess, source_file))
+}
+
+/// Given a session and a `source_file`, return a parser. Returns any buffered errors from lexing the
+/// initial token stream.
+fn maybe_source_file_to_parser(
+    sess: &ParseSess,
+    source_file: Lrc<SourceFile>,
+) -> Result<Parser<'_>, Vec<Diagnostic>> {
+    let end_pos = source_file.end_pos;
+    let (stream, unclosed_delims) = maybe_file_to_stream(sess, source_file, None)?;
+    let mut parser = stream_to_parser(sess, stream, None);
+    parser.unclosed_delims = unclosed_delims;
+    if parser.token == token::Eof {
+        parser.token.span = Span::new(end_pos, end_pos, parser.token.span.ctxt(), None);
+    }
+
+    Ok(parser)
+}
+
+// Base abstractions
+
+/// Given a session and a path and an optional span (for error reporting),
+/// add the path to the session's source_map and return the new source_file or
+/// error when a file can't be read.
+fn try_file_to_source_file(
+    sess: &ParseSess,
+    path: &Path,
+    spanopt: Option<Span>,
+) -> Result<Lrc<SourceFile>, Diagnostic> {
+    sess.source_map().load_file(path).map_err(|e| {
+        let msg = format!("couldn't read {}: {}", path.display(), e);
+        let mut diag = Diagnostic::new(Level::Fatal, &msg);
+        if let Some(sp) = spanopt {
+            diag.set_span(sp);
+        }
+        diag
+    })
+}
+
+/// Given a session and a path and an optional span (for error reporting),
+/// adds the path to the session's `source_map` and returns the new `source_file`.
+fn file_to_source_file(sess: &ParseSess, path: &Path, spanopt: Option<Span>) -> Lrc<SourceFile> {
+    match try_file_to_source_file(sess, path, spanopt) {
+        Ok(source_file) => source_file,
+        Err(mut d) => {
+            sess.span_diagnostic.emit_diagnostic(&mut d);
+            FatalError.raise();
+        }
+    }
+}
+
+/// Given a `source_file`, produces a sequence of token trees.
+pub fn source_file_to_stream(
+    sess: &ParseSess,
+    source_file: Lrc<SourceFile>,
+    override_span: Option<Span>,
+) -> (TokenStream, Vec<lexer::UnmatchedBrace>) {
+    panictry_buffer!(&sess.span_diagnostic, maybe_file_to_stream(sess, source_file, override_span))
+}
+
+/// Given a source file, produces a sequence of token trees. Returns any buffered errors from
+/// parsing the token stream.
+pub fn maybe_file_to_stream(
+    sess: &ParseSess,
+    source_file: Lrc<SourceFile>,
+    override_span: Option<Span>,
+) -> Result<(TokenStream, Vec<lexer::UnmatchedBrace>), Vec<Diagnostic>> {
+    let src = source_file.src.as_ref().unwrap_or_else(|| {
+        sess.span_diagnostic.bug(&format!(
+            "cannot lex `source_file` without source: {}",
+            sess.source_map().filename_for_diagnostics(&source_file.name)
+        ));
+    });
+
+    let (token_trees, unmatched_braces) =
+        lexer::parse_token_trees(sess, src.as_str(), source_file.start_pos, override_span);
+
+    match token_trees {
+        Ok(stream) => Ok((stream, unmatched_braces)),
+        Err(err) => {
+            let mut buffer = Vec::with_capacity(1);
+            err.buffer(&mut buffer);
+            // Not using `emit_unclosed_delims` to use `db.buffer`
+            for unmatched in unmatched_braces {
+                if let Some(err) = make_unclosed_delims_error(unmatched, &sess) {
+                    err.buffer(&mut buffer);
+                }
+            }
+            Err(buffer)
+        }
+    }
+}
+
+/// Given a stream and the `ParseSess`, produces a parser.
+pub fn stream_to_parser<'a>(
+    sess: &'a ParseSess,
+    stream: TokenStream,
+    subparser_name: Option<&'static str>,
+) -> Parser<'a> {
+    Parser::new(sess, stream, false, subparser_name)
+}
+
+/// Runs the given subparser `f` on the tokens of the given `attr`'s item.
+pub fn parse_in<'a, T>(
+    sess: &'a ParseSess,
+    tts: TokenStream,
+    name: &'static str,
+    mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+) -> PResult<'a, T> {
+    let mut parser = Parser::new(sess, tts, false, Some(name));
+    let result = f(&mut parser)?;
+    if parser.token != token::Eof {
+        parser.unexpected()?;
+    }
+    Ok(result)
+}
+
+pub fn fake_token_stream_for_item(sess: &ParseSess, item: &ast::Item) -> TokenStream {
+    let source = pprust::item_to_string(item);
+    let filename = FileName::macro_expansion_source_code(&source);
+    parse_stream_from_source_str(filename, source, sess, Some(item.span))
+}
+
+pub fn fake_token_stream_for_crate(sess: &ParseSess, krate: &ast::Crate) -> TokenStream {
+    let source = pprust::crate_to_string_for_macros(krate);
+    let filename = FileName::macro_expansion_source_code(&source);
+    parse_stream_from_source_str(filename, source, sess, Some(krate.spans.inner_span))
+}
+
+pub fn parse_cfg_attr(
+    attr: &Attribute,
+    parse_sess: &ParseSess,
+) -> Option<(MetaItem, Vec<(AttrItem, Span)>)> {
+    match attr.get_normal_item().args {
+        ast::MacArgs::Delimited(dspan, delim, ref tts) if !tts.is_empty() => {
+            let msg = "wrong `cfg_attr` delimiters";
+            crate::validate_attr::check_meta_bad_delim(parse_sess, dspan, delim, msg);
+            match parse_in(parse_sess, tts.clone(), "`cfg_attr` input", |p| p.parse_cfg_attr()) {
+                Ok(r) => return Some(r),
+                Err(mut e) => {
+                    e.help(&format!("the valid syntax is `{}`", CFG_ATTR_GRAMMAR_HELP))
+                        .note(CFG_ATTR_NOTE_REF)
+                        .emit();
+                }
+            }
+        }
+        _ => error_malformed_cfg_attr_missing(attr.span, parse_sess),
+    }
+    None
+}
+
+const CFG_ATTR_GRAMMAR_HELP: &str = "#[cfg_attr(condition, attribute, other_attribute, ...)]";
+const CFG_ATTR_NOTE_REF: &str = "for more information, visit \
+    <https://doc.rust-lang.org/reference/conditional-compilation.html\
+    #the-cfg_attr-attribute>";
+
+fn error_malformed_cfg_attr_missing(span: Span, parse_sess: &ParseSess) {
+    parse_sess
+        .span_diagnostic
+        .struct_span_err(span, "malformed `cfg_attr` attribute input")
+        .span_suggestion(
+            span,
+            "missing condition and attribute",
+            CFG_ATTR_GRAMMAR_HELP,
+            Applicability::HasPlaceholders,
+        )
+        .note(CFG_ATTR_NOTE_REF)
+        .emit();
+}