[rustc.git] / vendor / rustc-ap-rustc_expand / src / mbe / quoted.rs

use crate::mbe::macro_parser;
use crate::mbe::{Delimited, KleeneOp, KleeneToken, SequenceRepetition, TokenTree};

use rustc_ast::token::{self, Token};
use rustc_ast::tokenstream;
use rustc_ast::{NodeId, DUMMY_NODE_ID};
use rustc_ast_pretty::pprust;
use rustc_feature::Features;
use rustc_session::parse::{feature_err, ParseSess};
use rustc_span::symbol::{kw, sym, Ident};

use rustc_span::Span;

use rustc_data_structures::sync::Lrc;

const VALID_FRAGMENT_NAMES_MSG: &str = "valid fragment specifiers are \
                                        `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, \
                                        `literal`, `path`, `meta`, `tt`, `item` and `vis`";

/// Takes a `tokenstream::TokenStream` and returns a `Vec<self::TokenTree>`. Specifically, this
/// takes a generic `TokenStream`, such as is used in the rest of the compiler, and returns a
/// collection of `TokenTree` for use in parsing a macro.
///
/// # Parameters
///
/// - `input`: a token stream to read from, the contents of which we are parsing.
/// - `expect_matchers`: `parse` can be used to parse either the "patterns" or the "body" of a
///   macro. Both take roughly the same form _except_ that in a pattern, metavars are declared with
///   their "matcher" type. For example `$var:expr` or `$id:ident`. In this example, `expr` and
///   `ident` are "matchers". They are not present in the body of a macro rule -- just in the
///   pattern, so we pass a parameter to indicate whether to expect them or not.
/// - `sess`: the parsing session. Any errors will be emitted to this session.
/// - `node_id`: the NodeId of the macro we are parsing.
/// - `features`: language features so we can do feature gating.
///
/// # Returns
///
/// A collection of `self::TokenTree`. There may also be some errors emitted to `sess`.
pub(super) fn parse(
    input: tokenstream::TokenStream,
    expect_matchers: bool,
    sess: &ParseSess,
    node_id: NodeId,
    features: &Features,
) -> Vec<TokenTree> {
    // Will contain the final collection of `self::TokenTree`
    let mut result = Vec::new();

    // For each token tree in `input`, parse the token into a `self::TokenTree`, consuming
    // additional trees if need be.
    let mut trees = input.trees();
    while let Some(tree) = trees.next() {
        // Given the parsed tree, if there is a metavar and we are expecting matchers, actually
        // parse out the matcher (i.e., in `$id:ident` this would parse the `:` and `ident`).
        let tree = parse_tree(tree, &mut trees, expect_matchers, sess, node_id, features);
        match tree {
            TokenTree::MetaVar(start_sp, ident) if expect_matchers => {
                let span = match trees.next() {
                    Some(tokenstream::TokenTree::Token(Token { kind: token::Colon, span })) => {
                        match trees.next() {
                            Some(tokenstream::TokenTree::Token(token)) => match token.ident() {
                                Some((frag, _)) => {
                                    let span = token.span.with_lo(start_sp.lo());

                                    match frag.name {
                                        sym::pat2018 | sym::pat2021 => {
                                            if !features.edition_macro_pats {
                                                feature_err(
                                                    sess,
                                                    sym::edition_macro_pats,
                                                    frag.span,
                                                    "`pat2018` and `pat2021` are unstable.",
                                                )
                                                .emit();
                                            }
                                        }
                                        _ => {}
                                    }

                                    let kind =
                                        token::NonterminalKind::from_symbol(frag.name, || {
                                            span.edition()
                                        })
                                        .unwrap_or_else(
                                            || {
                                                let msg = format!(
                                                    "invalid fragment specifier `{}`",
                                                    frag.name
                                                );
                                                sess.span_diagnostic
                                                    .struct_span_err(span, &msg)
                                                    .help(VALID_FRAGMENT_NAMES_MSG)
                                                    .emit();
                                                token::NonterminalKind::Ident
                                            },
                                        );
                                    result.push(TokenTree::MetaVarDecl(span, ident, Some(kind)));
                                    continue;
                                }
                                _ => token.span,
                            },
                            tree => tree.as_ref().map_or(span, tokenstream::TokenTree::span),
                        }
                    }
                    tree => tree.as_ref().map_or(start_sp, tokenstream::TokenTree::span),
                };
                if node_id != DUMMY_NODE_ID {
                    // Macros loaded from other crates have dummy node ids.
                    sess.missing_fragment_specifiers.borrow_mut().insert(span, node_id);
                }
                result.push(TokenTree::MetaVarDecl(span, ident, None));
            }

            // Not a metavar or no matchers allowed, so just return the tree
            _ => result.push(tree),
        }
    }
    result
}

/// Takes a `tokenstream::TokenTree` and returns a `self::TokenTree`. Specifically, this takes a
/// generic `TokenTree`, such as is used in the rest of the compiler, and returns a `TokenTree`
/// for use in parsing a macro.
///
/// Converting the given tree may involve reading more tokens.
///
/// # Parameters
///
/// - `tree`: the tree we wish to convert.
/// - `outer_trees`: an iterator over trees. We may need to read more tokens from it in order to finish
///   converting `tree`
/// - `expect_matchers`: same as for `parse` (see above).
/// - `sess`: the parsing session. Any errors will be emitted to this session.
/// - `features`: language features so we can do feature gating.
fn parse_tree(
    tree: tokenstream::TokenTree,
    outer_trees: &mut impl Iterator<Item = tokenstream::TokenTree>,
    expect_matchers: bool,
    sess: &ParseSess,
    node_id: NodeId,
    features: &Features,
) -> TokenTree {
    // Depending on what `tree` is, we could be parsing different parts of a macro
    match tree {
        // `tree` is a `$` token. Look at the next token in `trees`
        tokenstream::TokenTree::Token(Token { kind: token::Dollar, span }) => {
            // FIXME: Handle `None`-delimited groups in a more systematic way
            // during parsing.
            let mut next = outer_trees.next();
            let mut trees: Box<dyn Iterator<Item = tokenstream::TokenTree>>;
            if let Some(tokenstream::TokenTree::Delimited(_, token::NoDelim, tts)) = next {
                trees = Box::new(tts.into_trees());
                next = trees.next();
            } else {
                trees = Box::new(outer_trees);
            }

            match next {
                // `tree` is followed by a delimited set of token trees. This indicates the beginning
                // of a repetition sequence in the macro (e.g. `$(pat)*`).
                Some(tokenstream::TokenTree::Delimited(span, delim, tts)) => {
                    // Must have `(` not `{` or `[`
                    if delim != token::Paren {
                        let tok = pprust::token_kind_to_string(&token::OpenDelim(delim));
                        let msg = format!("expected `(`, found `{}`", tok);
                        sess.span_diagnostic.span_err(span.entire(), &msg);
                    }
                    // Parse the contents of the sequence itself
                    let sequence = parse(tts, expect_matchers, sess, node_id, features);
                    // Get the Kleene operator and optional separator
                    let (separator, kleene) =
                        parse_sep_and_kleene_op(&mut trees, span.entire(), sess);
                    // Count the number of captured "names" (i.e., named metavars)
                    let name_captures = macro_parser::count_names(&sequence);
                    TokenTree::Sequence(
                        span,
                        Lrc::new(SequenceRepetition {
                            tts: sequence,
                            separator,
                            kleene,
                            num_captures: name_captures,
                        }),
                    )
                }

                // `tree` is followed by an `ident`. This could be `$meta_var` or the `$crate` special
                // metavariable that names the crate of the invocation.
                Some(tokenstream::TokenTree::Token(token)) if token.is_ident() => {
                    let (ident, is_raw) = token.ident().unwrap();
                    let span = ident.span.with_lo(span.lo());
                    if ident.name == kw::Crate && !is_raw {
                        TokenTree::token(token::Ident(kw::DollarCrate, is_raw), span)
                    } else {
                        TokenTree::MetaVar(span, ident)
                    }
                }

                // `tree` is followed by a random token. This is an error.
                Some(tokenstream::TokenTree::Token(token)) => {
                    let msg = format!(
                        "expected identifier, found `{}`",
                        pprust::token_to_string(&token),
                    );
                    sess.span_diagnostic.span_err(token.span, &msg);
                    TokenTree::MetaVar(token.span, Ident::invalid())
                }

                // There are no more tokens. Just return the `$` we already have.
                None => TokenTree::token(token::Dollar, span),
            }
        }

        // `tree` is an arbitrary token. Keep it.
        tokenstream::TokenTree::Token(token) => TokenTree::Token(token),

        // `tree` is the beginning of a delimited set of tokens (e.g., `(` or `{`). We need to
        // descend into the delimited set and further parse it.
        tokenstream::TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
            span,
            Lrc::new(Delimited {
                delim,
                tts: parse(tts, expect_matchers, sess, node_id, features),
            }),
        ),
    }
}

/// Takes a token and returns `Some(KleeneOp)` if the token is `+` `*` or `?`. Otherwise, return
/// `None`.
fn kleene_op(token: &Token) -> Option<KleeneOp> {
    match token.kind {
        token::BinOp(token::Star) => Some(KleeneOp::ZeroOrMore),
        token::BinOp(token::Plus) => Some(KleeneOp::OneOrMore),
        token::Question => Some(KleeneOp::ZeroOrOne),
        _ => None,
    }
}

/// Parse the next token tree of the input looking for a KleeneOp. Returns
///
/// - Ok(Ok((op, span))) if the next token tree is a KleeneOp
/// - Ok(Err(tok, span)) if the next token tree is a token but not a KleeneOp
/// - Err(span) if the next token tree is not a token
fn parse_kleene_op(
    input: &mut impl Iterator<Item = tokenstream::TokenTree>,
    span: Span,
) -> Result<Result<(KleeneOp, Span), Token>, Span> {
    match input.next() {
        Some(tokenstream::TokenTree::Token(token)) => match kleene_op(&token) {
            Some(op) => Ok(Ok((op, token.span))),
            None => Ok(Err(token)),
        },
        tree => Err(tree.as_ref().map_or(span, tokenstream::TokenTree::span)),
    }
}

/// Attempt to parse a single Kleene star, possibly with a separator.
///
/// For example, in a pattern such as `$(a),*`, `a` is the pattern to be repeated, `,` is the
/// separator, and `*` is the Kleene operator. This function is specifically concerned with parsing
/// the last two tokens of such a pattern: namely, the optional separator and the Kleene operator
/// itself. Note that here we are parsing the _macro_ itself, rather than trying to match some
/// stream of tokens in an invocation of a macro.
///
/// This function will take some input iterator `input` corresponding to `span` and a parsing
/// session `sess`. If the next one (or possibly two) tokens in `input` correspond to a Kleene
/// operator and separator, then a tuple with `(separator, KleeneOp)` is returned. Otherwise, an
/// error with the appropriate span is emitted to `sess` and a dummy value is returned.
fn parse_sep_and_kleene_op(
    input: &mut impl Iterator<Item = tokenstream::TokenTree>,
    span: Span,
    sess: &ParseSess,
) -> (Option<Token>, KleeneToken) {
    // We basically look at two token trees here, denoted as #1 and #2 below
    let span = match parse_kleene_op(input, span) {
        // #1 is a `?`, `+`, or `*` KleeneOp
        Ok(Ok((op, span))) => return (None, KleeneToken::new(op, span)),

        // #1 is a separator followed by #2, a KleeneOp
        Ok(Err(token)) => match parse_kleene_op(input, token.span) {
            // #2 is the `?` Kleene op, which does not take a separator (error)
            Ok(Ok((KleeneOp::ZeroOrOne, span))) => {
                // Error!
                sess.span_diagnostic.span_err(
                    token.span,
                    "the `?` macro repetition operator does not take a separator",
                );

                // Return a dummy
                return (None, KleeneToken::new(KleeneOp::ZeroOrMore, span));
            }

            // #2 is a KleeneOp :D
            Ok(Ok((op, span))) => return (Some(token), KleeneToken::new(op, span)),

            // #2 is a random token or not a token at all :(
            Ok(Err(Token { span, .. })) | Err(span) => span,
        },

        // #1 is not a token
        Err(span) => span,
    };

    // If we ever get to this point, we have experienced an "unexpected token" error
    sess.span_diagnostic.span_err(span, "expected one of: `*`, `+`, or `?`");

    // Return a dummy
    (None, KleeneToken::new(KleeneOp::ZeroOrMore, span))
}
Commit	Line	Data
f20569fa XL	1	use crate::mbe::macro_parser;
	2	use crate::mbe::{Delimited, KleeneOp, KleeneToken, SequenceRepetition, TokenTree};
	3
	4	use rustc_ast::token::{self, Token};
	5	use rustc_ast::tokenstream;
	6	use rustc_ast::{NodeId, DUMMY_NODE_ID};
	7	use rustc_ast_pretty::pprust;
	8	use rustc_feature::Features;
	9	use rustc_session::parse::{feature_err, ParseSess};
	10	use rustc_span::symbol::{kw, sym, Ident};
	11
	12	use rustc_span::Span;
	13
	14	use rustc_data_structures::sync::Lrc;
	15
	16	const VALID_FRAGMENT_NAMES_MSG: &str = "valid fragment specifiers are \
	17	`ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, \
	18	`literal`, `path`, `meta`, `tt`, `item` and `vis`";
	19
	20	/// Takes a `tokenstream::TokenStream` and returns a `Vec<self::TokenTree>`. Specifically, this
	21	/// takes a generic `TokenStream`, such as is used in the rest of the compiler, and returns a
	22	/// collection of `TokenTree` for use in parsing a macro.
	23	///
	24	/// # Parameters
	25	///
	26	/// - `input`: a token stream to read from, the contents of which we are parsing.
	27	/// - `expect_matchers`: `parse` can be used to parse either the "patterns" or the "body" of a
	28	/// macro. Both take roughly the same form _except_ that in a pattern, metavars are declared with
	29	/// their "matcher" type. For example `$var:expr` or `$id:ident`. In this example, `expr` and
	30	/// `ident` are "matchers". They are not present in the body of a macro rule -- just in the
	31	/// pattern, so we pass a parameter to indicate whether to expect them or not.
	32	/// - `sess`: the parsing session. Any errors will be emitted to this session.
	33	/// - `node_id`: the NodeId of the macro we are parsing.
	34	/// - `features`: language features so we can do feature gating.
	35	///
	36	/// # Returns
	37	///
	38	/// A collection of `self::TokenTree`. There may also be some errors emitted to `sess`.
	39	pub(super) fn parse(
	40	input: tokenstream::TokenStream,
	41	expect_matchers: bool,
	42	sess: &ParseSess,
	43	node_id: NodeId,
	44	features: &Features,
	45	) -> Vec<TokenTree> {
	46	// Will contain the final collection of `self::TokenTree`
	47	let mut result = Vec::new();
	48
	49	// For each token tree in `input`, parse the token into a `self::TokenTree`, consuming
	50	// additional trees if need be.
	51	let mut trees = input.trees();
	52	while let Some(tree) = trees.next() {
	53	// Given the parsed tree, if there is a metavar and we are expecting matchers, actually
	54	// parse out the matcher (i.e., in `$id:ident` this would parse the `:` and `ident`).
	55	let tree = parse_tree(tree, &mut trees, expect_matchers, sess, node_id, features);
	56	match tree {
	57	TokenTree::MetaVar(start_sp, ident) if expect_matchers => {
	58	let span = match trees.next() {
	59	Some(tokenstream::TokenTree::Token(Token { kind: token::Colon, span })) => {
	60	match trees.next() {
	61	Some(tokenstream::TokenTree::Token(token)) => match token.ident() {
	62	Some((frag, _)) => {
	63	let span = token.span.with_lo(start_sp.lo());
	64
65	match frag.name {
66	sym::pat2018 \| sym::pat2021 => {
67	if !features.edition_macro_pats {
68	feature_err(
69	sess,
70	sym::edition_macro_pats,
71	frag.span,
72	"`pat2018` and `pat2021` are unstable.",
73	)
74	.emit();
75	}
76	}
77	_ => {}
78	}
79
80	let kind =
81	token::NonterminalKind::from_symbol(frag.name, \|\| {
82	span.edition()
83	})
84	.unwrap_or_else(
85	\|\| {
86	let msg = format!(
87	"invalid fragment specifier `{}`",
88	frag.name
89	);
90	sess.span_diagnostic
91	.struct_span_err(span, &msg)
92	.help(VALID_FRAGMENT_NAMES_MSG)
93	.emit();
94	token::NonterminalKind::Ident
95	},
96	);
97	result.push(TokenTree::MetaVarDecl(span, ident, Some(kind)));
98	continue;
99	}
100	_ => token.span,
101	},
102	tree => tree.as_ref().map_or(span, tokenstream::TokenTree::span),
103	}
104	}
105	tree => tree.as_ref().map_or(start_sp, tokenstream::TokenTree::span),
106	};
107	if node_id != DUMMY_NODE_ID {
108	// Macros loaded from other crates have dummy node ids.
109	sess.missing_fragment_specifiers.borrow_mut().insert(span, node_id);
110	}
111	result.push(TokenTree::MetaVarDecl(span, ident, None));
112	}
113
114	// Not a metavar or no matchers allowed, so just return the tree
115	_ => result.push(tree),
116	}
117	}
118	result
119	}
120
121	/// Takes a `tokenstream::TokenTree` and returns a `self::TokenTree`. Specifically, this takes a
122	/// generic `TokenTree`, such as is used in the rest of the compiler, and returns a `TokenTree`
123	/// for use in parsing a macro.
124	///
125	/// Converting the given tree may involve reading more tokens.
126	///
127	/// # Parameters
128	///
129	/// - `tree`: the tree we wish to convert.
130	/// - `outer_trees`: an iterator over trees. We may need to read more tokens from it in order to finish
131	/// converting `tree`
132	/// - `expect_matchers`: same as for `parse` (see above).
133	/// - `sess`: the parsing session. Any errors will be emitted to this session.
134	/// - `features`: language features so we can do feature gating.
135	fn parse_tree(
136	tree: tokenstream::TokenTree,
137	outer_trees: &mut impl Iterator<Item = tokenstream::TokenTree>,
138	expect_matchers: bool,
139	sess: &ParseSess,
140	node_id: NodeId,
141	features: &Features,
142	) -> TokenTree {
143	// Depending on what `tree` is, we could be parsing different parts of a macro
144	match tree {
145	// `tree` is a `$` token. Look at the next token in `trees`
146	tokenstream::TokenTree::Token(Token { kind: token::Dollar, span }) => {
147	// FIXME: Handle `None`-delimited groups in a more systematic way
148	// during parsing.
149	let mut next = outer_trees.next();
150	let mut trees: Box<dyn Iterator<Item = tokenstream::TokenTree>>;
151	if let Some(tokenstream::TokenTree::Delimited(_, token::NoDelim, tts)) = next {
152	trees = Box::new(tts.into_trees());
153	next = trees.next();
154	} else {
155	trees = Box::new(outer_trees);
156	}
157
158	match next {
159	// `tree` is followed by a delimited set of token trees. This indicates the beginning
160	// of a repetition sequence in the macro (e.g. `$(pat)*`).
161	Some(tokenstream::TokenTree::Delimited(span, delim, tts)) => {
162	// Must have `(` not `{` or `[`
163	if delim != token::Paren {
164	let tok = pprust::token_kind_to_string(&token::OpenDelim(delim));
165	let msg = format!("expected `(`, found `{}`", tok);
166	sess.span_diagnostic.span_err(span.entire(), &msg);
167	}
168	// Parse the contents of the sequence itself
169	let sequence = parse(tts, expect_matchers, sess, node_id, features);
170	// Get the Kleene operator and optional separator
171	let (separator, kleene) =
172	parse_sep_and_kleene_op(&mut trees, span.entire(), sess);
173	// Count the number of captured "names" (i.e., named metavars)
174	let name_captures = macro_parser::count_names(&sequence);
175	TokenTree::Sequence(
176	span,
177	Lrc::new(SequenceRepetition {
178	tts: sequence,
179	separator,
180	kleene,
181	num_captures: name_captures,
182	}),
183	)
184	}
185
186	// `tree` is followed by an `ident`. This could be `$meta_var` or the `$crate` special
187	// metavariable that names the crate of the invocation.
188	Some(tokenstream::TokenTree::Token(token)) if token.is_ident() => {
189	let (ident, is_raw) = token.ident().unwrap();
190	let span = ident.span.with_lo(span.lo());
191	if ident.name == kw::Crate && !is_raw {
192	TokenTree::token(token::Ident(kw::DollarCrate, is_raw), span)
193	} else {
194	TokenTree::MetaVar(span, ident)
195	}
196	}
197
198	// `tree` is followed by a random token. This is an error.
199	Some(tokenstream::TokenTree::Token(token)) => {
200	let msg = format!(
201	"expected identifier, found `{}`",
202	pprust::token_to_string(&token),
203	);
204	sess.span_diagnostic.span_err(token.span, &msg);
205	TokenTree::MetaVar(token.span, Ident::invalid())
206	}
207
208	// There are no more tokens. Just return the `$` we already have.
209	None => TokenTree::token(token::Dollar, span),
210	}
211	}
212
213	// `tree` is an arbitrary token. Keep it.
214	tokenstream::TokenTree::Token(token) => TokenTree::Token(token),
215
216	// `tree` is the beginning of a delimited set of tokens (e.g., `(` or `{`). We need to
217	// descend into the delimited set and further parse it.
218	tokenstream::TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
219	span,
220	Lrc::new(Delimited {
221	delim,
222	tts: parse(tts, expect_matchers, sess, node_id, features),
223	}),
224	),
225	}
226	}
227
228	/// Takes a token and returns `Some(KleeneOp)` if the token is `+` `*` or `?`. Otherwise, return
229	/// `None`.
230	fn kleene_op(token: &Token) -> Option<KleeneOp> {
231	match token.kind {
232	token::BinOp(token::Star) => Some(KleeneOp::ZeroOrMore),
233	token::BinOp(token::Plus) => Some(KleeneOp::OneOrMore),
234	token::Question => Some(KleeneOp::ZeroOrOne),
235	_ => None,
236	}
237	}
238
239	/// Parse the next token tree of the input looking for a KleeneOp. Returns
240	///
241	/// - Ok(Ok((op, span))) if the next token tree is a KleeneOp
242	/// - Ok(Err(tok, span)) if the next token tree is a token but not a KleeneOp
243	/// - Err(span) if the next token tree is not a token
244	fn parse_kleene_op(
245	input: &mut impl Iterator<Item = tokenstream::TokenTree>,
246	span: Span,
247	) -> Result<Result<(KleeneOp, Span), Token>, Span> {
248	match input.next() {
249	Some(tokenstream::TokenTree::Token(token)) => match kleene_op(&token) {
250	Some(op) => Ok(Ok((op, token.span))),
251	None => Ok(Err(token)),
252	},
253	tree => Err(tree.as_ref().map_or(span, tokenstream::TokenTree::span)),
254	}
255	}
256
257	/// Attempt to parse a single Kleene star, possibly with a separator.
258	///
259	/// For example, in a pattern such as `$(a),*`, `a` is the pattern to be repeated, `,` is the
260	/// separator, and `*` is the Kleene operator. This function is specifically concerned with parsing
261	/// the last two tokens of such a pattern: namely, the optional separator and the Kleene operator
262	/// itself. Note that here we are parsing the _macro_ itself, rather than trying to match some
263	/// stream of tokens in an invocation of a macro.
264	///
265	/// This function will take some input iterator `input` corresponding to `span` and a parsing
266	/// session `sess`. If the next one (or possibly two) tokens in `input` correspond to a Kleene
267	/// operator and separator, then a tuple with `(separator, KleeneOp)` is returned. Otherwise, an
268	/// error with the appropriate span is emitted to `sess` and a dummy value is returned.
269	fn parse_sep_and_kleene_op(
270	input: &mut impl Iterator<Item = tokenstream::TokenTree>,
271	span: Span,
272	sess: &ParseSess,
273	) -> (Option<Token>, KleeneToken) {
274	// We basically look at two token trees here, denoted as #1 and #2 below
275	let span = match parse_kleene_op(input, span) {
276	// #1 is a `?`, `+`, or `*` KleeneOp
277	Ok(Ok((op, span))) => return (None, KleeneToken::new(op, span)),
278
279	// #1 is a separator followed by #2, a KleeneOp
280	Ok(Err(token)) => match parse_kleene_op(input, token.span) {
281	// #2 is the `?` Kleene op, which does not take a separator (error)
282	Ok(Ok((KleeneOp::ZeroOrOne, span))) => {
283	// Error!
284	sess.span_diagnostic.span_err(
285	token.span,
286	"the `?` macro repetition operator does not take a separator",
287	);
288
289	// Return a dummy
290	return (None, KleeneToken::new(KleeneOp::ZeroOrMore, span));
291	}
292
293	// #2 is a KleeneOp :D
294	Ok(Ok((op, span))) => return (Some(token), KleeneToken::new(op, span)),
295
296	// #2 is a random token or not a token at all :(
297	Ok(Err(Token { span, .. })) \| Err(span) => span,
298	},
299
300	// #1 is not a token
301	Err(span) => span,
302	};
303
304	// If we ever get to this point, we have experienced an "unexpected token" error
305	sess.span_diagnostic.span_err(span, "expected one of: `*`, `+`, or `?`");
306
307	// Return a dummy
308	(None, KleeneToken::new(KleeneOp::ZeroOrMore, span))
309	}