      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

    /// Parse the input TokenStream of a macro, triggering a compile error if the
    /// tokens fail to parse.
    ///
    /// Refer to the [`parse` module] documentation for more details about parsing
    /// in Syn.
    ///
    /// [`parse` module]: crate::rustdoc_workaround::parse_module
    ///
    /// <br>
    ///
    /// # Intended usage
    ///
    /// This macro must be called from a function that returns
    /// `proc_macro::TokenStream`. Usually this will be your proc macro entry point,
    /// the function that has the #\[proc_macro\] / #\[proc_macro_derive\] /
    /// #\[proc_macro_attribute\] attribute.
    ///
    /// ```
    /// # extern crate proc_macro;
    /// #
    /// use proc_macro::TokenStream;
    /// use syn::{parse_macro_input, Result};
    /// use syn::parse::{Parse, ParseStream};
    ///
    /// struct MyMacroInput {
    ///     /* ... */
    /// }
    ///
    /// impl Parse for MyMacroInput {
    ///     fn parse(input: ParseStream) -> Result<Self> {
    ///         /* ... */
    /// #       Ok(MyMacroInput {})
    ///     }
    /// }
    ///
    /// # const IGNORE: &str = stringify! {
    /// #[proc_macro]
    /// # };
    /// pub fn my_macro(tokens: TokenStream) -> TokenStream {
    ///     let input = parse_macro_input!(tokens as MyMacroInput);
    ///
    ///     /* ... */
    /// #   "".parse().unwrap()
    /// }
    /// ```
    ///
    /// <br>
    ///
    /// # Usage with Parser
    ///
    /// This macro can also be used with the [`Parser` trait] for types that have
    /// multiple ways that they can be parsed.
    ///
    /// [`Parser` trait]: crate::rustdoc_workaround::parse_module::Parser
    ///
    /// ```
    /// # extern crate proc_macro;
    /// #
    /// # use proc_macro::TokenStream;
    /// # use syn::{parse_macro_input, Result};
    /// # use syn::parse::ParseStream;
    /// #
    /// # struct MyMacroInput {}
    /// #
    /// impl MyMacroInput {
    ///     fn parse_alternate(input: ParseStream) -> Result<Self> {
    ///         /* ... */
    /// #       Ok(MyMacroInput {})
    ///     }
    /// }
    ///
    /// # const IGNORE: &str = stringify! {
    /// #[proc_macro]
    /// # };
    /// pub fn my_macro(tokens: TokenStream) -> TokenStream {
    ///     let input = parse_macro_input!(tokens with MyMacroInput::parse_alternate);
    ///
    ///     /* ... */
    /// #   "".parse().unwrap()
    /// }
    /// ```
    ///
    /// <br>
    ///
    /// # Expansion
    ///
    /// `parse_macro_input!($variable as $Type)` expands to something like:
    ///
    /// ```no_run
    /// # extern crate proc_macro;
    /// #
    /// # macro_rules! doc_test {
    /// #     ($variable:ident as $Type:ty) => {
    /// match syn::parse::<$Type>($variable) {
    ///     Ok(syntax_tree) => syntax_tree,
    ///     Err(err) => return proc_macro::TokenStream::from(err.to_compile_error()),
    /// }
    /// #     };
    /// # }
    /// #
    /// # fn test(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    /// #     let _ = doc_test!(input as syn::Ident);
    /// #     proc_macro::TokenStream::new()
    /// # }
    /// ```
    #[macro_export]
    #[cfg_attr(doc_cfg, doc(cfg(all(feature = "parsing", feature = "proc-macro"))))]
    macro_rules! parse_macro_input {
        ($tokenstream:ident as $ty:ty) => {
            match $crate::parse_macro_input::parse::<$ty>($tokenstream) {
                $crate::__private::Ok(data) => data,
                $crate::__private::Err(err) => {
                    return $crate::__private::TokenStream::from(err.to_compile_error());
                }
            }
        };
        ($tokenstream:ident with $parser:path) => {
            match $crate::parse::Parser::parse($parser, $tokenstream) {
                $crate::__private::Ok(data) => data,
                $crate::__private::Err(err) => {
                    return $crate::__private::TokenStream::from(err.to_compile_error());
                }
            }
        };
        ($tokenstream:ident) => {
            $crate::parse_macro_input!($tokenstream as _)
        };
    }

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

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

    // Not public API.
    #[doc(hidden)]
    pub fn parse<T: ParseMacroInput>(token_stream: TokenStream) -> Result<T> {
        T::parse.parse(token_stream)
    }

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

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

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

    #[cfg(any(feature = "full", feature = "derive"))]
    use crate::AttributeArgs;

    #[cfg(any(feature = "full", feature = "derive"))]
    impl ParseMacroInput for AttributeArgs {
        fn parse(input: ParseStream) -> Result<Self> {
            let mut metas = Vec::new();

            loop {
                if input.is_empty() {
                    break;
                }
                let value = input.parse()?;
                metas.push(value);
                if input.is_empty() {
                    break;
                }
                input.parse::<Token![,]>()?;
            }

            Ok(metas)
        }
    }