1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
|
use rustc_ast::token::{self, BinOpToken, Delimiter};
use rustc_ast::tokenstream::{TokenStream, TokenTree};
use rustc_ast_pretty::pprust::state::State as Printer;
use rustc_ast_pretty::pprust::PrintState;
use rustc_middle::ty::TyCtxt;
use rustc_session::parse::ParseSess;
use rustc_span::source_map::FilePathMapping;
use rustc_span::symbol::{kw, Ident, Symbol};
use rustc_span::Span;
/// Render a macro matcher in a format suitable for displaying to the user
/// as part of an item declaration.
pub(super) fn render_macro_matcher(tcx: TyCtxt<'_>, matcher: &TokenTree) -> String {
if let Some(snippet) = snippet_equal_to_token(tcx, matcher) {
// If the original source code is known, we display the matcher exactly
// as present in the source code.
return snippet;
}
// If the matcher is macro-generated or some other reason the source code
// snippet is not available, we attempt to nicely render the token tree.
let mut printer = Printer::new();
// If the inner ibox fits on one line, we get:
//
// macro_rules! macroname {
// (the matcher) => {...};
// }
//
// If the inner ibox gets wrapped, the cbox will break and get indented:
//
// macro_rules! macroname {
// (
// the matcher ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~!
// ) => {...};
// }
printer.cbox(8);
printer.word("(");
printer.zerobreak();
printer.ibox(0);
match matcher {
TokenTree::Delimited(_span, _delim, tts) => print_tts(&mut printer, tts),
// Matcher which is not a Delimited is unexpected and should've failed
// to compile, but we render whatever it is wrapped in parens.
TokenTree::Token(..) => print_tt(&mut printer, matcher),
}
printer.end();
printer.break_offset_if_not_bol(0, -4);
printer.word(")");
printer.end();
printer.s.eof()
}
/// Find the source snippet for this token's Span, reparse it, and return the
/// snippet if the reparsed TokenTree matches the argument TokenTree.
fn snippet_equal_to_token(tcx: TyCtxt<'_>, matcher: &TokenTree) -> Option<String> {
// Find what rustc thinks is the source snippet.
// This may not actually be anything meaningful if this matcher was itself
// generated by a macro.
let source_map = tcx.sess.source_map();
let span = matcher.span();
let snippet = source_map.span_to_snippet(span).ok()?;
// Create a Parser.
let sess =
ParseSess::new(rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec(), FilePathMapping::empty());
let file_name = source_map.span_to_filename(span);
let mut parser =
match rustc_parse::maybe_new_parser_from_source_str(&sess, file_name, snippet.clone()) {
Ok(parser) => parser,
Err(diagnostics) => {
drop(diagnostics);
return None;
}
};
// Reparse a single token tree.
if parser.token == token::Eof {
return None;
}
let reparsed_tree = parser.parse_token_tree();
if parser.token != token::Eof {
return None;
}
// Compare against the original tree.
if reparsed_tree.eq_unspanned(matcher) { Some(snippet) } else { None }
}
fn print_tt(printer: &mut Printer<'_>, tt: &TokenTree) {
match tt {
TokenTree::Token(token, _) => {
let token_str = printer.token_to_string(token);
printer.word(token_str);
if let token::DocComment(..) = token.kind {
printer.hardbreak()
}
}
TokenTree::Delimited(_span, delim, tts) => {
let open_delim = printer.token_kind_to_string(&token::OpenDelim(*delim));
printer.word(open_delim);
if !tts.is_empty() {
if *delim == Delimiter::Brace {
printer.space();
}
print_tts(printer, tts);
if *delim == Delimiter::Brace {
printer.space();
}
}
let close_delim = printer.token_kind_to_string(&token::CloseDelim(*delim));
printer.word(close_delim);
}
}
}
fn print_tts(printer: &mut Printer<'_>, tts: &TokenStream) {
#[derive(Copy, Clone, PartialEq)]
enum State {
Start,
Dollar,
DollarIdent,
DollarIdentColon,
DollarParen,
DollarParenSep,
Pound,
PoundBang,
Ident,
Other,
}
use State::*;
let mut state = Start;
for tt in tts.trees() {
let (needs_space, next_state) = match &tt {
TokenTree::Token(tt, _) => match (state, &tt.kind) {
(Dollar, token::Ident(..)) => (false, DollarIdent),
(DollarIdent, token::Colon) => (false, DollarIdentColon),
(DollarIdentColon, token::Ident(..)) => (false, Other),
(
DollarParen,
token::BinOp(BinOpToken::Plus | BinOpToken::Star) | token::Question,
) => (false, Other),
(DollarParen, _) => (false, DollarParenSep),
(DollarParenSep, token::BinOp(BinOpToken::Plus | BinOpToken::Star)) => {
(false, Other)
}
(Pound, token::Not) => (false, PoundBang),
(_, token::Ident(symbol, /* is_raw */ false))
if !usually_needs_space_between_keyword_and_open_delim(*symbol, tt.span) =>
{
(true, Ident)
}
(_, token::Comma | token::Semi) => (false, Other),
(_, token::Dollar) => (true, Dollar),
(_, token::Pound) => (true, Pound),
(_, _) => (true, Other),
},
TokenTree::Delimited(_, delim, _) => match (state, delim) {
(Dollar, Delimiter::Parenthesis) => (false, DollarParen),
(Pound | PoundBang, Delimiter::Bracket) => (false, Other),
(Ident, Delimiter::Parenthesis | Delimiter::Bracket) => (false, Other),
(_, _) => (true, Other),
},
};
if state != Start && needs_space {
printer.space();
}
print_tt(printer, tt);
state = next_state;
}
}
fn usually_needs_space_between_keyword_and_open_delim(symbol: Symbol, span: Span) -> bool {
let ident = Ident { name: symbol, span };
let is_keyword = ident.is_used_keyword() || ident.is_unused_keyword();
if !is_keyword {
// An identifier that is not a keyword usually does not need a space
// before an open delim. For example: `f(0)` or `f[0]`.
return false;
}
match symbol {
// No space after keywords that are syntactically an expression. For
// example: a tuple struct created with `let _ = Self(0, 0)`, or if
// someone has `impl Index<MyStruct> for bool` then `true[MyStruct]`.
kw::False | kw::SelfLower | kw::SelfUpper | kw::True => false,
// No space, as in `let _: fn();`
kw::Fn => false,
// No space, as in `pub(crate) type T;`
kw::Pub => false,
// No space for keywords that can end an expression, as in `fut.await()`
// where fut's Output type is `fn()`.
kw::Await => false,
// Otherwise space after keyword. Some examples:
//
// `expr as [T; 2]`
// ^
// `box (tuple,)`
// ^
// `break (tuple,)`
// ^
// `type T = dyn (Fn() -> dyn Trait) + Send;`
// ^
// `for (tuple,) in iter {}`
// ^
// `if (tuple,) == v {}`
// ^
// `impl [T] {}`
// ^
// `for x in [..] {}`
// ^
// `let () = unit;`
// ^
// `match [x, y] {...}`
// ^
// `&mut (x as T)`
// ^
// `return [];`
// ^
// `fn f<T>() where (): Into<T>`
// ^
// `while (a + b).what() {}`
// ^
// `yield [];`
// ^
_ => true,
}
}
|
