rust/compiler/rustc_parse/src/lib.rs

//! The main parser interface.

#![allow(internal_features)]
#![allow(rustc::diagnostic_outside_of_impl)]
#![allow(rustc::untranslatable_diagnostic)]
#![feature(array_windows)]
#![feature(box_patterns)]
#![feature(debug_closure_helpers)]
#![feature(if_let_guard)]
#![feature(iter_intersperse)]
#![feature(let_chains)]

#[macro_use]
extern crate tracing;

use rustc_ast as ast;
use rustc_ast::token;
use rustc_ast::tokenstream::TokenStream;
use rustc_ast::{AttrItem, Attribute, MetaItem};
use rustc_ast_pretty::pprust;
use rustc_data_structures::sync::Lrc;
use rustc_errors::{Diag, FatalError, 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::{make_unclosed_delims_error, Parser};
pub mod lexer;
pub mod validate_attr;

mod errors;

rustc_fluent_macro::fluent_messages! { "../messages.ftl" }

// 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<Diag>` instead of a single `Diag`.
macro_rules! panictry_buffer {
    ($e:expr) => {{
        use std::result::Result::{Err, Ok};
        match $e {
            Ok(e) => e,
            Err(errs) => {
                for e in errs {
                    e.emit();
                }
                FatalError.raise()
            }
        }
    }};
}

pub fn parse_crate_from_file<'a>(input: &Path, psess: &'a ParseSess) -> PResult<'a, ast::Crate> {
    let mut parser = new_parser_from_file(psess, input, None);
    parser.parse_crate_mod()
}

pub fn parse_crate_attrs_from_file<'a>(
    input: &Path,
    psess: &'a ParseSess,
) -> PResult<'a, ast::AttrVec> {
    let mut parser = new_parser_from_file(psess, input, None);
    parser.parse_inner_attributes()
}

pub fn parse_crate_from_source_str(
    name: FileName,
    source: String,
    psess: &ParseSess,
) -> PResult<'_, ast::Crate> {
    new_parser_from_source_str(psess, name, source).parse_crate_mod()
}

pub fn parse_crate_attrs_from_source_str(
    name: FileName,
    source: String,
    psess: &ParseSess,
) -> PResult<'_, ast::AttrVec> {
    new_parser_from_source_str(psess, name, source).parse_inner_attributes()
}

pub fn parse_stream_from_source_str(
    name: FileName,
    source: String,
    psess: &ParseSess,
    override_span: Option<Span>,
) -> TokenStream {
    source_file_to_stream(psess, psess.source_map().new_source_file(name, source), override_span)
}

/// Creates a new parser from a source string.
pub fn new_parser_from_source_str(psess: &ParseSess, name: FileName, source: String) -> Parser<'_> {
    panictry_buffer!(maybe_new_parser_from_source_str(psess, name, source))
}

/// Creates a new parser from a source string. Returns any buffered errors from lexing the initial
/// token stream; these must be consumed via `emit`, `cancel`, etc., otherwise a panic will occur
/// when they are dropped.
pub fn maybe_new_parser_from_source_str(
    psess: &ParseSess,
    name: FileName,
    source: String,
) -> Result<Parser<'_>, Vec<Diag<'_>>> {
    maybe_source_file_to_parser(psess, psess.source_map().new_source_file(name, source))
}

/// Creates a new parser, aborting 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>(psess: &'a ParseSess, path: &Path, sp: Option<Span>) -> Parser<'a> {
    let source_file = psess.source_map().load_file(path).unwrap_or_else(|e| {
        let msg = format!("couldn't read {}: {}", path.display(), e);
        let mut err = psess.dcx.struct_fatal(msg);
        if let Some(sp) = sp {
            err.span(sp);
        }
        err.emit();
    });

    panictry_buffer!(maybe_source_file_to_parser(psess, 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(
    psess: &ParseSess,
    source_file: Lrc<SourceFile>,
) -> Result<Parser<'_>, Vec<Diag<'_>>> {
    let end_pos = source_file.end_position();
    let stream = maybe_file_to_stream(psess, source_file, None)?;
    let mut parser = stream_to_parser(psess, stream, None);
    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 `source_file`, produces a sequence of token trees.
pub fn source_file_to_stream(
    psess: &ParseSess,
    source_file: Lrc<SourceFile>,
    override_span: Option<Span>,
) -> TokenStream {
    panictry_buffer!(maybe_file_to_stream(psess, source_file, override_span))
}

/// Given a source file, produces a sequence of token trees. Returns any buffered errors from
/// parsing the token stream.
fn maybe_file_to_stream<'psess>(
    psess: &'psess ParseSess,
    source_file: Lrc<SourceFile>,
    override_span: Option<Span>,
) -> Result<TokenStream, Vec<Diag<'psess>>> {
    let src = source_file.src.as_ref().unwrap_or_else(|| {
        psess.dcx.bug(format!(
            "cannot lex `source_file` without source: {}",
            psess.source_map().filename_for_diagnostics(&source_file.name)
        ));
    });

    lexer::parse_token_trees(psess, src.as_str(), source_file.start_pos, override_span)
}

/// Given a stream and the `ParseSess`, produces a parser.
pub fn stream_to_parser<'a>(
    psess: &'a ParseSess,
    stream: TokenStream,
    subparser_name: Option<&'static str>,
) -> Parser<'a> {
    Parser::new(psess, stream, subparser_name)
}

/// Runs the given subparser `f` on the tokens of the given `attr`'s item.
pub fn parse_in<'a, T>(
    psess: &'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(psess, tts, Some(name));
    let result = f(&mut parser)?;
    if parser.token != token::Eof {
        parser.unexpected()?;
    }
    Ok(result)
}

pub fn fake_token_stream_for_item(psess: &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, psess, Some(item.span))
}

pub fn fake_token_stream_for_crate(psess: &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, psess, Some(krate.spans.inner_span))
}

pub fn parse_cfg_attr(
    attr: &Attribute,
    psess: &ParseSess,
) -> Option<(MetaItem, Vec<(AttrItem, Span)>)> {
    match attr.get_normal_item().args {
        ast::AttrArgs::Delimited(ast::DelimArgs { dspan, delim, ref tokens })
            if !tokens.is_empty() =>
        {
            crate::validate_attr::check_cfg_attr_bad_delim(psess, dspan, delim);
            match parse_in(psess, tokens.clone(), "`cfg_attr` input", |p| p.parse_cfg_attr()) {
                Ok(r) => return Some(r),
                Err(e) => {
                    e.with_help(format!("the valid syntax is `{CFG_ATTR_GRAMMAR_HELP}`"))
                        .with_note(CFG_ATTR_NOTE_REF)
                        .emit();
                }
            }
        }
        _ => error_malformed_cfg_attr_missing(attr.span, psess),
    }
    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, psess: &ParseSess) {
    psess.dcx.emit_err(errors::MalformedCfgAttr { span, sugg: CFG_ATTR_GRAMMAR_HELP });
}