prettyplease/
generics.rs

1use crate::algorithm::Printer;
2use crate::iter::IterDelimited;
3use crate::path::PathKind;
4use crate::INDENT;
5use proc_macro2::TokenStream;
6use std::ptr;
7use syn::{
8    BoundLifetimes, ConstParam, GenericParam, Generics, LifetimeParam, PredicateLifetime,
9    PredicateType, TraitBound, TraitBoundModifier, TypeParam, TypeParamBound, WhereClause,
10    WherePredicate,
11};
12
13impl Printer {
14    pub fn generics(&mut self, generics: &Generics) {
15        if generics.params.is_empty() {
16            return;
17        }
18
19        self.word("<");
20        self.cbox(0);
21        self.zerobreak();
22
23        // Print lifetimes before types and consts, regardless of their
24        // order in self.params.
25        #[derive(Ord, PartialOrd, Eq, PartialEq)]
26        enum Group {
27            First,
28            Second,
29        }
30        fn group(param: &GenericParam) -> Group {
31            match param {
32                GenericParam::Lifetime(_) => Group::First,
33                GenericParam::Type(_) | GenericParam::Const(_) => Group::Second,
34            }
35        }
36        let last = generics.params.iter().max_by_key(|param| group(param));
37        for current_group in [Group::First, Group::Second] {
38            for param in &generics.params {
39                if group(param) == current_group {
40                    self.generic_param(param);
41                    self.trailing_comma(ptr::eq(param, last.unwrap()));
42                }
43            }
44        }
45
46        self.offset(-INDENT);
47        self.end();
48        self.word(">");
49    }
50
51    fn generic_param(&mut self, generic_param: &GenericParam) {
52        match generic_param {
53            GenericParam::Type(type_param) => self.type_param(type_param),
54            GenericParam::Lifetime(lifetime_param) => self.lifetime_param(lifetime_param),
55            GenericParam::Const(const_param) => self.const_param(const_param),
56        }
57    }
58
59    pub fn bound_lifetimes(&mut self, bound_lifetimes: &BoundLifetimes) {
60        self.word("for<");
61        for param in bound_lifetimes.lifetimes.iter().delimited() {
62            self.generic_param(&param);
63            if !param.is_last {
64                self.word(", ");
65            }
66        }
67        self.word("> ");
68    }
69
70    fn lifetime_param(&mut self, lifetime_param: &LifetimeParam) {
71        self.outer_attrs(&lifetime_param.attrs);
72        self.lifetime(&lifetime_param.lifetime);
73        for lifetime in lifetime_param.bounds.iter().delimited() {
74            if lifetime.is_first {
75                self.word(": ");
76            } else {
77                self.word(" + ");
78            }
79            self.lifetime(&lifetime);
80        }
81    }
82
83    fn type_param(&mut self, type_param: &TypeParam) {
84        self.outer_attrs(&type_param.attrs);
85        self.ident(&type_param.ident);
86        self.ibox(INDENT);
87        for type_param_bound in type_param.bounds.iter().delimited() {
88            if type_param_bound.is_first {
89                self.word(": ");
90            } else {
91                self.space();
92                self.word("+ ");
93            }
94            self.type_param_bound(&type_param_bound);
95        }
96        if let Some(default) = &type_param.default {
97            self.space();
98            self.word("= ");
99            self.ty(default);
100        }
101        self.end();
102    }
103
104    pub fn type_param_bound(&mut self, type_param_bound: &TypeParamBound) {
105        match type_param_bound {
106            TypeParamBound::Trait(trait_bound) => {
107                let tilde_const = false;
108                self.trait_bound(trait_bound, tilde_const);
109            }
110            TypeParamBound::Lifetime(lifetime) => self.lifetime(lifetime),
111            TypeParamBound::Verbatim(bound) => self.type_param_bound_verbatim(bound),
112            #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
113            _ => unimplemented!("unknown TypeParamBound"),
114        }
115    }
116
117    fn trait_bound(&mut self, trait_bound: &TraitBound, tilde_const: bool) {
118        if trait_bound.paren_token.is_some() {
119            self.word("(");
120        }
121        if tilde_const {
122            self.word("~const ");
123        }
124        self.trait_bound_modifier(&trait_bound.modifier);
125        if let Some(bound_lifetimes) = &trait_bound.lifetimes {
126            self.bound_lifetimes(bound_lifetimes);
127        }
128        for segment in trait_bound.path.segments.iter().delimited() {
129            if !segment.is_first || trait_bound.path.leading_colon.is_some() {
130                self.word("::");
131            }
132            self.path_segment(&segment, PathKind::Type);
133        }
134        if trait_bound.paren_token.is_some() {
135            self.word(")");
136        }
137    }
138
139    fn trait_bound_modifier(&mut self, trait_bound_modifier: &TraitBoundModifier) {
140        match trait_bound_modifier {
141            TraitBoundModifier::None => {}
142            TraitBoundModifier::Maybe(_question_mark) => self.word("?"),
143        }
144    }
145
146    #[cfg(not(feature = "verbatim"))]
147    fn type_param_bound_verbatim(&mut self, bound: &TokenStream) {
148        unimplemented!("TypeParamBound::Verbatim `{}`", bound);
149    }
150
151    #[cfg(feature = "verbatim")]
152    fn type_param_bound_verbatim(&mut self, tokens: &TokenStream) {
153        use syn::parse::{Parse, ParseStream, Result};
154        use syn::{parenthesized, token, Token};
155
156        enum TypeParamBoundVerbatim {
157            TildeConst(TraitBound),
158        }
159
160        impl Parse for TypeParamBoundVerbatim {
161            fn parse(input: ParseStream) -> Result<Self> {
162                let content;
163                let (paren_token, content) = if input.peek(token::Paren) {
164                    (Some(parenthesized!(content in input)), &content)
165                } else {
166                    (None, input)
167                };
168                content.parse::<Token![~]>()?;
169                content.parse::<Token![const]>()?;
170                let mut bound: TraitBound = content.parse()?;
171                bound.paren_token = paren_token;
172                Ok(TypeParamBoundVerbatim::TildeConst(bound))
173            }
174        }
175
176        let bound: TypeParamBoundVerbatim = match syn::parse2(tokens.clone()) {
177            Ok(bound) => bound,
178            Err(_) => unimplemented!("TypeParamBound::Verbatim `{}`", tokens),
179        };
180
181        match bound {
182            TypeParamBoundVerbatim::TildeConst(trait_bound) => {
183                let tilde_const = true;
184                self.trait_bound(&trait_bound, tilde_const);
185            }
186        }
187    }
188
189    fn const_param(&mut self, const_param: &ConstParam) {
190        self.outer_attrs(&const_param.attrs);
191        self.word("const ");
192        self.ident(&const_param.ident);
193        self.word(": ");
194        self.ty(&const_param.ty);
195        if let Some(default) = &const_param.default {
196            self.word(" = ");
197            self.expr(default);
198        }
199    }
200
201    pub fn where_clause_for_body(&mut self, where_clause: &Option<WhereClause>) {
202        let hardbreaks = true;
203        let semi = false;
204        self.where_clause_impl(where_clause, hardbreaks, semi);
205    }
206
207    pub fn where_clause_semi(&mut self, where_clause: &Option<WhereClause>) {
208        let hardbreaks = true;
209        let semi = true;
210        self.where_clause_impl(where_clause, hardbreaks, semi);
211    }
212
213    pub fn where_clause_oneline(&mut self, where_clause: &Option<WhereClause>) {
214        let hardbreaks = false;
215        let semi = false;
216        self.where_clause_impl(where_clause, hardbreaks, semi);
217    }
218
219    pub fn where_clause_oneline_semi(&mut self, where_clause: &Option<WhereClause>) {
220        let hardbreaks = false;
221        let semi = true;
222        self.where_clause_impl(where_clause, hardbreaks, semi);
223    }
224
225    fn where_clause_impl(
226        &mut self,
227        where_clause: &Option<WhereClause>,
228        hardbreaks: bool,
229        semi: bool,
230    ) {
231        let where_clause = match where_clause {
232            Some(where_clause) if !where_clause.predicates.is_empty() => where_clause,
233            _ => {
234                if semi {
235                    self.word(";");
236                } else {
237                    self.nbsp();
238                }
239                return;
240            }
241        };
242        if hardbreaks {
243            self.hardbreak();
244            self.offset(-INDENT);
245            self.word("where");
246            self.hardbreak();
247            for predicate in where_clause.predicates.iter().delimited() {
248                self.where_predicate(&predicate);
249                if predicate.is_last && semi {
250                    self.word(";");
251                } else {
252                    self.word(",");
253                    self.hardbreak();
254                }
255            }
256            if !semi {
257                self.offset(-INDENT);
258            }
259        } else {
260            self.space();
261            self.offset(-INDENT);
262            self.word("where");
263            self.space();
264            for predicate in where_clause.predicates.iter().delimited() {
265                self.where_predicate(&predicate);
266                if predicate.is_last && semi {
267                    self.word(";");
268                } else {
269                    self.trailing_comma_or_space(predicate.is_last);
270                }
271            }
272            if !semi {
273                self.offset(-INDENT);
274            }
275        }
276    }
277
278    fn where_predicate(&mut self, predicate: &WherePredicate) {
279        match predicate {
280            WherePredicate::Type(predicate) => self.predicate_type(predicate),
281            WherePredicate::Lifetime(predicate) => self.predicate_lifetime(predicate),
282            #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
283            _ => unimplemented!("unknown WherePredicate"),
284        }
285    }
286
287    fn predicate_type(&mut self, predicate: &PredicateType) {
288        if let Some(bound_lifetimes) = &predicate.lifetimes {
289            self.bound_lifetimes(bound_lifetimes);
290        }
291        self.ty(&predicate.bounded_ty);
292        self.word(":");
293        if predicate.bounds.len() == 1 {
294            self.ibox(0);
295        } else {
296            self.ibox(INDENT);
297        }
298        for type_param_bound in predicate.bounds.iter().delimited() {
299            if type_param_bound.is_first {
300                self.nbsp();
301            } else {
302                self.space();
303                self.word("+ ");
304            }
305            self.type_param_bound(&type_param_bound);
306        }
307        self.end();
308    }
309
310    fn predicate_lifetime(&mut self, predicate: &PredicateLifetime) {
311        self.lifetime(&predicate.lifetime);
312        self.word(":");
313        self.ibox(INDENT);
314        for lifetime in predicate.bounds.iter().delimited() {
315            if lifetime.is_first {
316                self.nbsp();
317            } else {
318                self.space();
319                self.word("+ ");
320            }
321            self.lifetime(&lifetime);
322        }
323        self.end();
324    }
325}
prettyplease/generics.rs

prettyplease/
generics.rs
