rust/compiler/rustc_parse/src/lib.rs

//! The main parser interface.

#![feature(array_windows)]
#![feature(box_patterns)]
#![feature(if_let_guard)]
#![cfg_attr(bootstrap, 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();
}