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

/// Quasi-quotation macro that accepts input like the [`quote!`] macro but uses
/// type inference to figure out a return type for those tokens.
///
/// [`quote!`]: https://docs.rs/quote/1.0/quote/index.html
///
/// The return type can be any syntax tree node that implements the [`Parse`]
/// trait.
///
/// [`Parse`]: crate::parse::Parse
///
/// ```
/// use quote::quote;
/// use syn::{parse_quote, Stmt};
///
/// fn main() {
///     let name = quote!(v);
///     let ty = quote!(u8);
///
///     let stmt: Stmt = parse_quote! {
///         let #name: #ty = Default::default();
///     };
///
///     println!("{:#?}", stmt);
/// }
/// ```
///
/// *This macro is available only if Syn is built with the `"parsing"` feature,
/// although interpolation of syntax tree nodes into the quoted tokens is only
/// supported if Syn is built with the `"printing"` feature as well.*
///
/// # Example
///
/// The following helper function adds a bound `T: HeapSize` to every type
/// parameter `T` in the input generics.
///
/// ```
/// use syn::{parse_quote, Generics, GenericParam};
///
/// // Add a bound `T: HeapSize` to every type parameter T.
/// fn add_trait_bounds(mut generics: Generics) -> Generics {
///     for param in &mut generics.params {
///         if let GenericParam::Type(type_param) = param {
///             type_param.bounds.push(parse_quote!(HeapSize));
///         }
///     }
///     generics
/// }
/// ```
///
/// # Special cases
///
/// This macro can parse the following additional types as a special case even
/// though they do not implement the `Parse` trait.
///
/// - [`Attribute`] — parses one attribute, allowing either outer like `#[...]`
///   or inner like `#![...]`
/// - [`Punctuated<T, P>`] — parses zero or more `T` separated by punctuation
///   `P` with optional trailing punctuation
/// - [`Vec<Stmt>`] — parses the same as `Block::parse_within`
///
/// [`Vec<Stmt>`]: Block::parse_within
///
/// # Panics
///
/// Panics if the tokens fail to parse as the expected syntax tree type. The
/// caller is responsible for ensuring that the input tokens are syntactically
/// valid.
#[cfg_attr(doc_cfg, doc(cfg(all(feature = "parsing", feature = "printing"))))]
#[macro_export]
macro_rules! parse_quote {
    ($($tt:tt)*) => {
        $crate::parse_quote::parse($crate::__private::quote::quote!($($tt)*))
    };
}

/// This macro is [`parse_quote!`] + [`quote_spanned!`][quote::quote_spanned].
///
/// Please refer to each of their documentation.
///
/// # Example
///
/// ```
/// use quote::{quote, quote_spanned};
/// use syn::spanned::Spanned;
/// use syn::{parse_quote_spanned, ReturnType, Signature};
///
/// // Changes `fn()` to `fn() -> Pin<Box<dyn Future<Output = ()>>>`,
/// // and `fn() -> T` to `fn() -> Pin<Box<dyn Future<Output = T>>>`,
/// // without introducing any call_site() spans.
/// fn make_ret_pinned_future(sig: &mut Signature) {
///     let ret = match &sig.output {
///         ReturnType::Default => quote_spanned!(sig.paren_token.span=> ()),
///         ReturnType::Type(_, ret) => quote!(#ret),
///     };
///     sig.output = parse_quote_spanned! {ret.span()=>
///         -> ::std::pin::Pin<::std::boxed::Box<dyn ::std::future::Future<Output = #ret>>>
///     };
/// }
/// ```
#[cfg_attr(doc_cfg, doc(cfg(all(feature = "parsing", feature = "printing"))))]
#[macro_export]
macro_rules! parse_quote_spanned {
    ($span:expr=> $($tt:tt)*) => {
        $crate::parse_quote::parse($crate::__private::quote::quote_spanned!($span=> $($tt)*))
    };
}

////////////////////////////////////////////////////////////////////////////////
// Can parse any type that implements Parse.

use crate::parse::{Parse, ParseStream, Parser, Result};
use proc_macro2::TokenStream;

// Not public API.
#[doc(hidden)]
pub fn parse<T: ParseQuote>(token_stream: TokenStream) -> T {
    let parser = T::parse;
    match parser.parse2(token_stream) {
        Ok(t) => t,
        Err(err) => panic!("{}", err),
    }
}

// Not public API.
#[doc(hidden)]
pub trait ParseQuote: Sized {
    fn parse(input: ParseStream) -> Result<Self>;
}

impl<T: Parse> ParseQuote for T {
    fn parse(input: ParseStream) -> Result<Self> {
        <T as Parse>::parse(input)
    }
}

////////////////////////////////////////////////////////////////////////////////
// Any other types that we want `parse_quote!` to be able to parse.

use crate::punctuated::Punctuated;
#[cfg(any(feature = "full", feature = "derive"))]
use crate::{attr, Attribute};
#[cfg(feature = "full")]
use crate::{Block, Stmt};

#[cfg(any(feature = "full", feature = "derive"))]
impl ParseQuote for Attribute {
    fn parse(input: ParseStream) -> Result<Self> {
        if input.peek(Token![#]) && input.peek2(Token![!]) {
            attr::parsing::single_parse_inner(input)
        } else {
            attr::parsing::single_parse_outer(input)
        }
    }
}

impl<T: Parse, P: Parse> ParseQuote for Punctuated<T, P> {
    fn parse(input: ParseStream) -> Result<Self> {
        Self::parse_terminated(input)
    }
}

#[cfg(feature = "full")]
impl ParseQuote for Vec<Stmt> {
    fn parse(input: ParseStream) -> Result<Self> {
        Block::parse_within(input)
    }
}