Parse a pattern with no arm
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Nadrieril
parent
caa488b96e
commit
80bdcbf50a
36 changed files with 420 additions and 279 deletions
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@ -2899,127 +2899,155 @@ impl<'a> Parser<'a> {
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self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
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let lo = this.token.span;
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let (pat, guard) = this.parse_match_arm_pat_and_guard()?;
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let arrow_span = this.token.span;
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if let Err(mut err) = this.expect(&token::FatArrow) {
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// We might have a `=>` -> `=` or `->` typo (issue #89396).
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if TokenKind::FatArrow
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.similar_tokens()
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.is_some_and(|similar_tokens| similar_tokens.contains(&this.token.kind))
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{
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err.span_suggestion(
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this.token.span,
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"use a fat arrow to start a match arm",
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"=>",
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Applicability::MachineApplicable,
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);
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if matches!(
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(&this.prev_token.kind, &this.token.kind),
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(token::DotDotEq, token::Gt)
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) {
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// `error_inclusive_range_match_arrow` handles cases like `0..=> {}`,
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// so we suppress the error here
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err.delay_as_bug();
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} else {
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err.emit();
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}
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this.bump();
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} else {
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return Err(err);
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}
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}
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let arm_start_span = this.token.span;
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let expr = this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
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err.span_label(arrow_span, "while parsing the `match` arm starting here");
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err
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})?;
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let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
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&& this.token != token::CloseDelim(Delimiter::Brace);
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let hi = this.prev_token.span;
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if require_comma {
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let sm = this.sess.source_map();
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if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
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let span = body.span;
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return Ok((
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ast::Arm {
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attrs,
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pat,
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guard,
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body,
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span,
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id: DUMMY_NODE_ID,
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is_placeholder: false,
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},
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TrailingToken::None,
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));
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}
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let span_before_body = this.prev_token.span;
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let arm_body;
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let is_fat_arrow = this.check(&token::FatArrow);
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let is_almost_fat_arrow = TokenKind::FatArrow
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.similar_tokens()
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.is_some_and(|similar_tokens| similar_tokens.contains(&this.token.kind));
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let mut result = if !is_fat_arrow && !is_almost_fat_arrow {
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// A pattern without a body, allowed for never patterns.
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arm_body = None;
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this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
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.or_else(|mut err| {
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if this.token == token::FatArrow {
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if let Ok(expr_lines) = sm.span_to_lines(expr.span)
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&& let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
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&& arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
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&& expr_lines.lines.len() == 2
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{
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// We check whether there's any trailing code in the parse span,
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// if there isn't, we very likely have the following:
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//
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// X | &Y => "y"
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// | -- - missing comma
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// | |
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// | arrow_span
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// X | &X => "x"
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// | - ^^ self.token.span
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// | |
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// | parsed until here as `"y" & X`
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err.span_suggestion_short(
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arm_start_span.shrink_to_hi(),
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"missing a comma here to end this `match` arm",
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",",
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Applicability::MachineApplicable,
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);
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return Err(err);
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}
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} else {
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// FIXME(compiler-errors): We could also recover `; PAT =>` here
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// Try to parse a following `PAT =>`, if successful
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// then we should recover.
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let mut snapshot = this.create_snapshot_for_diagnostic();
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let pattern_follows = snapshot
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.parse_pat_allow_top_alt(
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None,
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RecoverComma::Yes,
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RecoverColon::Yes,
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CommaRecoveryMode::EitherTupleOrPipe,
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)
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.map_err(|err| err.cancel())
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.is_ok();
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if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
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err.cancel();
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this.sess.emit_err(errors::MissingCommaAfterMatchArm {
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span: hi.shrink_to_hi(),
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});
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return Ok(true);
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}
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}
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err.span_label(arrow_span, "while parsing the `match` arm starting here");
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Err(err)
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})?;
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} else {
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this.eat(&token::Comma);
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if let Err(mut err) = this.expect(&token::FatArrow) {
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// We might have a `=>` -> `=` or `->` typo (issue #89396).
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if is_almost_fat_arrow {
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err.span_suggestion(
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this.token.span,
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"use a fat arrow to start a match arm",
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"=>",
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Applicability::MachineApplicable,
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);
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if matches!(
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(&this.prev_token.kind, &this.token.kind),
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(token::DotDotEq, token::Gt)
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) {
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// `error_inclusive_range_match_arrow` handles cases like `0..=> {}`,
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// so we suppress the error here
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err.delay_as_bug();
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} else {
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err.emit();
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}
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this.bump();
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} else {
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return Err(err);
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}
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}
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let arrow_span = this.prev_token.span;
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let arm_start_span = this.token.span;
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let expr =
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this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
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err.span_label(arrow_span, "while parsing the `match` arm starting here");
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err
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})?;
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let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
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&& this.token != token::CloseDelim(Delimiter::Brace);
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if !require_comma {
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arm_body = Some(expr);
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this.eat(&token::Comma);
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Ok(false)
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} else if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
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arm_body = Some(body);
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Ok(true)
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} else {
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let expr_span = expr.span;
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arm_body = Some(expr);
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this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
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.map_err(|mut err| {
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if this.token == token::FatArrow {
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let sm = this.sess.source_map();
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if let Ok(expr_lines) = sm.span_to_lines(expr_span)
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&& let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
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&& arm_start_lines.lines[0].end_col
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== expr_lines.lines[0].end_col
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&& expr_lines.lines.len() == 2
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{
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// We check whether there's any trailing code in the parse span,
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// if there isn't, we very likely have the following:
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//
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// X | &Y => "y"
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// | -- - missing comma
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// | |
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// | arrow_span
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// X | &X => "x"
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// | - ^^ self.token.span
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// | |
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// | parsed until here as `"y" & X`
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err.span_suggestion_short(
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arm_start_span.shrink_to_hi(),
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"missing a comma here to end this `match` arm",
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",",
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Applicability::MachineApplicable,
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);
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}
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} else {
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err.span_label(
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arrow_span,
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"while parsing the `match` arm starting here",
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);
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}
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err
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})
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}
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};
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let hi_span = arm_body.as_ref().map_or(span_before_body, |body| body.span);
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let arm_span = lo.to(hi_span);
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// We want to recover:
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// X | Some(_) => foo()
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// | - missing comma
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// X | None => "x"
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// | ^^^^ self.token.span
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// as well as:
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// X | Some(!)
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// | - missing comma
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// X | None => "x"
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// | ^^^^ self.token.span
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// But we musn't recover
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// X | pat[0] => {}
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// | ^ self.token.span
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let recover_missing_comma = arm_body.is_some() || pat.could_be_never_pattern();
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if recover_missing_comma {
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result = result.or_else(|err| {
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// FIXME(compiler-errors): We could also recover `; PAT =>` here
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// Try to parse a following `PAT =>`, if successful
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// then we should recover.
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let mut snapshot = this.create_snapshot_for_diagnostic();
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let pattern_follows = snapshot
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.parse_pat_allow_top_alt(
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None,
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RecoverComma::Yes,
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RecoverColon::Yes,
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CommaRecoveryMode::EitherTupleOrPipe,
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)
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.map_err(|err| err.cancel())
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.is_ok();
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if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
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err.cancel();
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this.sess.emit_err(errors::MissingCommaAfterMatchArm {
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span: arm_span.shrink_to_hi(),
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});
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return Ok(true);
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}
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Err(err)
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});
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}
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result?;
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Ok((
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ast::Arm {
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attrs,
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pat,
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guard,
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body: expr,
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span: lo.to(hi),
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body: arm_body,
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span: arm_span,
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id: DUMMY_NODE_ID,
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is_placeholder: false,
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},
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