1 | // This file is part of ICU4X. For terms of use, please see the file |
2 | // called LICENSE at the top level of the ICU4X source tree |
3 | // (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ). |
4 | |
5 | //! Visitor for determining whether a type has type and non-static lifetime parameters |
6 | //! (duplicated in yoke/derive/src/visitor.rs) |
7 | |
8 | use std::collections::HashMap; |
9 | use syn::visit::{visit_lifetime, visit_type, visit_type_path, Visit}; |
10 | use syn::{Ident, Lifetime, Type, TypePath}; |
11 | |
12 | struct TypeVisitor<'a> { |
13 | /// The type parameters in scope |
14 | typarams: &'a HashMap<Ident, Option<Ident>>, |
15 | /// Whether we found a type parameter |
16 | found_typarams: bool, |
17 | /// Whether we found a non-'static lifetime parameter |
18 | found_lifetimes: bool, |
19 | } |
20 | |
21 | impl<'a, 'ast> Visit<'ast> for TypeVisitor<'a> { |
22 | fn visit_lifetime(&mut self, lt: &'ast Lifetime) { |
23 | if lt.ident != "static" { |
24 | self.found_lifetimes = true; |
25 | } |
26 | visit_lifetime(self, node:lt) |
27 | } |
28 | fn visit_type_path(&mut self, ty: &'ast TypePath) { |
29 | // We only need to check ty.path.get_ident() and not ty.qself or any |
30 | // generics in ty.path because the visitor will eventually visit those |
31 | // types on its own |
32 | if let Some(ident: &Ident) = ty.path.get_ident() { |
33 | if let Some(maybe_borrowed: &Option) = self.typarams.get(ident) { |
34 | self.found_typarams = true; |
35 | if maybe_borrowed.is_some() { |
36 | self.found_lifetimes = true; |
37 | } |
38 | } |
39 | } |
40 | |
41 | visit_type_path(self, node:ty) |
42 | } |
43 | } |
44 | |
45 | /// Checks if a type has type or lifetime parameters, given the local context of |
46 | /// named type parameters. Returns (has_type_params, has_lifetime_params) |
47 | pub fn check_type_for_parameters( |
48 | ty: &Type, |
49 | typarams: &HashMap<Ident, Option<Ident>>, |
50 | ) -> (bool, bool) { |
51 | let mut visit: TypeVisitor<'_> = TypeVisitor { |
52 | typarams, |
53 | found_typarams: false, |
54 | found_lifetimes: false, |
55 | }; |
56 | visit_type(&mut visit, node:ty); |
57 | |
58 | (visit.found_typarams, visit.found_lifetimes) |
59 | } |
60 | |
61 | #[cfg (test)] |
62 | mod tests { |
63 | use proc_macro2::Span; |
64 | use std::collections::HashMap; |
65 | use syn::{parse_quote, Ident}; |
66 | |
67 | use super::check_type_for_parameters; |
68 | fn make_typarams(params: &[&str]) -> HashMap<Ident, Option<Ident>> { |
69 | params |
70 | .iter() |
71 | .map(|x| (Ident::new(x, Span::call_site()), None)) |
72 | .collect() |
73 | } |
74 | |
75 | #[test ] |
76 | fn test_simple_type() { |
77 | let environment = make_typarams(&["T" , "U" , "V" ]); |
78 | |
79 | let ty = parse_quote!(Foo<'a, T>); |
80 | let check = check_type_for_parameters(&ty, &environment); |
81 | assert_eq!(check, (true, true)); |
82 | |
83 | let ty = parse_quote!(Foo<T>); |
84 | let check = check_type_for_parameters(&ty, &environment); |
85 | assert_eq!(check, (true, false)); |
86 | |
87 | let ty = parse_quote!(Foo<'static, T>); |
88 | let check = check_type_for_parameters(&ty, &environment); |
89 | assert_eq!(check, (true, false)); |
90 | |
91 | let ty = parse_quote!(Foo<'a>); |
92 | let check = check_type_for_parameters(&ty, &environment); |
93 | assert_eq!(check, (false, true)); |
94 | |
95 | let ty = parse_quote!(Foo<'a, Bar<U>, Baz<(V, u8)>>); |
96 | let check = check_type_for_parameters(&ty, &environment); |
97 | assert_eq!(check, (true, true)); |
98 | |
99 | let ty = parse_quote!(Foo<'a, W>); |
100 | let check = check_type_for_parameters(&ty, &environment); |
101 | assert_eq!(check, (false, true)); |
102 | } |
103 | |
104 | #[test ] |
105 | fn test_assoc_types() { |
106 | let environment = make_typarams(&["T" ]); |
107 | |
108 | let ty = parse_quote!(<Foo as SomeTrait<'a, T>>::Output); |
109 | let check = check_type_for_parameters(&ty, &environment); |
110 | assert_eq!(check, (true, true)); |
111 | |
112 | let ty = parse_quote!(<Foo as SomeTrait<'static, T>>::Output); |
113 | let check = check_type_for_parameters(&ty, &environment); |
114 | assert_eq!(check, (true, false)); |
115 | |
116 | let ty = parse_quote!(<T as SomeTrait<'static, Foo>>::Output); |
117 | let check = check_type_for_parameters(&ty, &environment); |
118 | assert_eq!(check, (true, false)); |
119 | } |
120 | } |
121 | |