use std::borrow::Cow;
use rustc_ast::token::{self, Token, TokenKind};
use rustc_ast::tokenstream::TokenStream;
use rustc_errors::{Applicability, Diag, DiagCtxtHandle, DiagMessage};
use rustc_macros::Subdiagnostic;
use rustc_parse::parser::{Parser, Recovery, token_descr};
use rustc_session::parse::ParseSess;
use rustc_span::source_map::SourceMap;
use rustc_span::symbol::Ident;
use rustc_span::{ErrorGuaranteed, Span};
use tracing::debug;
use super::macro_rules::{NoopTracker, parser_from_cx};
use crate::expand::{AstFragmentKind, parse_ast_fragment};
use crate::mbe::macro_parser::ParseResult::*;
use crate::mbe::macro_parser::{MatcherLoc, NamedParseResult, TtParser};
use crate::mbe::macro_rules::{Tracker, try_match_macro};
pub(super) fn failed_to_match_macro(
psess: &ParseSess,
sp: Span,
def_span: Span,
name: Ident,
arg: TokenStream,
lhses: &[Vec<MatcherLoc>],
) -> (Span, ErrorGuaranteed) {
let mut tracker = CollectTrackerAndEmitter::new(psess.dcx(), sp);
let try_success_result = try_match_macro(psess, name, &arg, lhses, &mut tracker);
if try_success_result.is_ok() {
assert!(
tracker.dcx.has_errors().is_some(),
"Macro matching returned a success on the second try"
);
}
if let Some(result) = tracker.result {
return result;
}
let Some(BestFailure { token, msg: label, remaining_matcher, .. }) = tracker.best_failure
else {
return (sp, psess.dcx().span_delayed_bug(sp, "failed to match a macro"));
};
let span = token.span.substitute_dummy(sp);
let mut err = psess.dcx().struct_span_err(span, parse_failure_msg(&token, None));
err.span_label(span, label);
if !def_span.is_dummy() && !psess.source_map().is_imported(def_span) {
err.span_label(psess.source_map().guess_head_span(def_span), "when calling this macro");
}
annotate_doc_comment(&mut err, psess.source_map(), span);
if let Some(span) = remaining_matcher.span() {
err.span_note(span, format!("while trying to match {remaining_matcher}"));
} else {
err.note(format!("while trying to match {remaining_matcher}"));
}
if let MatcherLoc::Token { token: expected_token } = &remaining_matcher
&& (matches!(expected_token.kind, TokenKind::Interpolated(_))
|| matches!(token.kind, TokenKind::Interpolated(_)))
{
err.note("captured metavariables except for `:tt`, `:ident` and `:lifetime` cannot be compared to other tokens");
err.note("see <https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment> for more information");
if !def_span.is_dummy() && !psess.source_map().is_imported(def_span) {
err.help("try using `:tt` instead in the macro definition");
}
}
if let Some((arg, comma_span)) = arg.add_comma() {
for lhs in lhses {
let parser = parser_from_cx(psess, arg.clone(), Recovery::Allowed);
let mut tt_parser = TtParser::new(name);
if let Success(_) =
tt_parser.parse_tt(&mut Cow::Borrowed(&parser), lhs, &mut NoopTracker)
{
if comma_span.is_dummy() {
err.note("you might be missing a comma");
} else {
err.span_suggestion_short(
comma_span,
"missing comma here",
", ",
Applicability::MachineApplicable,
);
}
}
}
}
let guar = err.emit();
(sp, guar)
}
struct CollectTrackerAndEmitter<'dcx, 'matcher> {
dcx: DiagCtxtHandle<'dcx>,
remaining_matcher: Option<&'matcher MatcherLoc>,
best_failure: Option<BestFailure>,
root_span: Span,
result: Option<(Span, ErrorGuaranteed)>,
}
struct BestFailure {
token: Token,
position_in_tokenstream: u32,
msg: &'static str,
remaining_matcher: MatcherLoc,
}
impl BestFailure {
fn is_better_position(&self, position: u32) -> bool {
position > self.position_in_tokenstream
}
}
impl<'dcx, 'matcher> Tracker<'matcher> for CollectTrackerAndEmitter<'dcx, 'matcher> {
type Failure = (Token, u32, &'static str);
fn build_failure(tok: Token, position: u32, msg: &'static str) -> Self::Failure {
(tok, position, msg)
}
fn before_match_loc(&mut self, parser: &TtParser, matcher: &'matcher MatcherLoc) {
if self.remaining_matcher.is_none()
|| (parser.has_no_remaining_items_for_step() && *matcher != MatcherLoc::Eof)
{
self.remaining_matcher = Some(matcher);
}
}
fn after_arm(&mut self, result: &NamedParseResult<Self::Failure>) {
match result {
Success(_) => {
self.dcx.span_delayed_bug(
self.root_span,
"should not collect detailed info for successful macro match",
);
}
Failure((token, approx_position, msg)) => {
debug!(?token, ?msg, "a new failure of an arm");
if self
.best_failure
.as_ref()
.map_or(true, |failure| failure.is_better_position(*approx_position))
{
self.best_failure = Some(BestFailure {
token: token.clone(),
position_in_tokenstream: *approx_position,
msg,
remaining_matcher: self
.remaining_matcher
.expect("must have collected matcher already")
.clone(),
})
}
}
Error(err_sp, msg) => {
let span = err_sp.substitute_dummy(self.root_span);
let guar = self.dcx.span_err(span, msg.clone());
self.result = Some((span, guar));
}
ErrorReported(guar) => self.result = Some((self.root_span, *guar)),
}
}
fn description() -> &'static str {
"detailed"
}
fn recovery() -> Recovery {
Recovery::Allowed
}
}
impl<'dcx> CollectTrackerAndEmitter<'dcx, '_> {
fn new(dcx: DiagCtxtHandle<'dcx>, root_span: Span) -> Self {
Self { dcx, remaining_matcher: None, best_failure: None, root_span, result: None }
}
}
pub(crate) struct FailureForwarder<'matcher> {
expected_token: Option<&'matcher Token>,
}
impl<'matcher> FailureForwarder<'matcher> {
pub(crate) fn new() -> Self {
Self { expected_token: None }
}
}
impl<'matcher> Tracker<'matcher> for FailureForwarder<'matcher> {
type Failure = (Token, u32, &'static str);
fn build_failure(tok: Token, position: u32, msg: &'static str) -> Self::Failure {
(tok, position, msg)
}
fn description() -> &'static str {
"failure-forwarder"
}
fn set_expected_token(&mut self, tok: &'matcher Token) {
self.expected_token = Some(tok);
}
fn get_expected_token(&self) -> Option<&'matcher Token> {
self.expected_token
}
}
pub(super) fn emit_frag_parse_err(
mut e: Diag<'_>,
parser: &Parser<'_>,
orig_parser: &mut Parser<'_>,
site_span: Span,
arm_span: Span,
kind: AstFragmentKind,
) -> ErrorGuaranteed {
if parser.token == token::Eof
&& let DiagMessage::Str(message) = &e.messages[0].0
&& message.ends_with(", found `<eof>`")
{
let msg = &e.messages[0];
e.messages[0] = (
DiagMessage::from(format!(
"macro expansion ends with an incomplete expression: {}",
message.replace(", found `<eof>`", ""),
)),
msg.1,
);
if !e.span.is_dummy() {
e.replace_span_with(parser.token.span.shrink_to_hi(), true);
}
}
if e.span.is_dummy() {
e.replace_span_with(site_span, true);
if !parser.psess.source_map().is_imported(arm_span) {
e.span_label(arm_span, "in this macro arm");
}
} else if parser.psess.source_map().is_imported(parser.token.span) {
e.span_label(site_span, "in this macro invocation");
}
match kind {
AstFragmentKind::Expr => match parse_ast_fragment(orig_parser, AstFragmentKind::Stmts) {
Err(err) => err.cancel(),
Ok(_) => {
e.note(
"the macro call doesn't expand to an expression, but it can expand to a statement",
);
if parser.token == token::Semi {
if let Ok(snippet) = parser.psess.source_map().span_to_snippet(site_span) {
e.span_suggestion_verbose(
site_span,
"surround the macro invocation with `{}` to interpret the expansion as a statement",
format!("{{ {snippet}; }}"),
Applicability::MaybeIncorrect,
);
}
} else {
e.span_suggestion_verbose(
site_span.shrink_to_hi(),
"add `;` to interpret the expansion as a statement",
";",
Applicability::MaybeIncorrect,
);
}
}
},
_ => annotate_err_with_kind(&mut e, kind, site_span),
};
e.emit()
}
pub(crate) fn annotate_err_with_kind(err: &mut Diag<'_>, kind: AstFragmentKind, span: Span) {
match kind {
AstFragmentKind::Ty => {
err.span_label(span, "this macro call doesn't expand to a type");
}
AstFragmentKind::Pat => {
err.span_label(span, "this macro call doesn't expand to a pattern");
}
_ => {}
};
}
#[derive(Subdiagnostic)]
enum ExplainDocComment {
#[label(expand_explain_doc_comment_inner)]
Inner {
#[primary_span]
span: Span,
},
#[label(expand_explain_doc_comment_outer)]
Outer {
#[primary_span]
span: Span,
},
}
pub(super) fn annotate_doc_comment(err: &mut Diag<'_>, sm: &SourceMap, span: Span) {
if let Ok(src) = sm.span_to_snippet(span) {
if src.starts_with("///") || src.starts_with("/**") {
err.subdiagnostic(ExplainDocComment::Outer { span });
} else if src.starts_with("//!") || src.starts_with("/*!") {
err.subdiagnostic(ExplainDocComment::Inner { span });
}
}
}
pub(super) fn parse_failure_msg(tok: &Token, expected_token: Option<&Token>) -> Cow<'static, str> {
if let Some(expected_token) = expected_token {
Cow::from(format!("expected {}, found {}", token_descr(expected_token), token_descr(tok)))
} else {
match tok.kind {
token::Eof => Cow::from("unexpected end of macro invocation"),
_ => Cow::from(format!("no rules expected {}", token_descr(tok))),
}
}
}