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Diffstat (limited to 'syn/src/mac.rs')
| -rw-r--r-- | syn/src/mac.rs | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/syn/src/mac.rs b/syn/src/mac.rs new file mode 100644 index 0000000..6c3dcae --- /dev/null +++ b/syn/src/mac.rs @@ -0,0 +1,239 @@ +use super::*; +use crate::token::{Brace, Bracket, Paren}; +use proc_macro2::TokenStream; +#[cfg(feature = "parsing")] +use proc_macro2::{Delimiter, Span, TokenTree}; + +#[cfg(feature = "parsing")] +use crate::parse::{Parse, ParseStream, Parser, Result}; +#[cfg(feature = "extra-traits")] +use crate::tt::TokenStreamHelper; +#[cfg(feature = "extra-traits")] +use std::hash::{Hash, Hasher}; + +ast_struct! { + /// A macro invocation: `println!("{}", mac)`. + /// + /// *This type is available if Syn is built with the `"derive"` or `"full"` + /// feature.* + pub struct Macro #manual_extra_traits { + pub path: Path, + pub bang_token: Token![!], + pub delimiter: MacroDelimiter, + pub tokens: TokenStream, + } +} + +ast_enum! { + /// A grouping token that surrounds a macro body: `m!(...)` or `m!{...}` or `m![...]`. + /// + /// *This type is available if Syn is built with the `"derive"` or `"full"` + /// feature.* + pub enum MacroDelimiter { + Paren(Paren), + Brace(Brace), + Bracket(Bracket), + } +} + +#[cfg(feature = "extra-traits")] +impl Eq for Macro {} + +#[cfg(feature = "extra-traits")] +impl PartialEq for Macro { + fn eq(&self, other: &Self) -> bool { + self.path == other.path + && self.bang_token == other.bang_token + && self.delimiter == other.delimiter + && TokenStreamHelper(&self.tokens) == TokenStreamHelper(&other.tokens) + } +} + +#[cfg(feature = "extra-traits")] +impl Hash for Macro { + fn hash<H>(&self, state: &mut H) + where + H: Hasher, + { + self.path.hash(state); + self.bang_token.hash(state); + self.delimiter.hash(state); + TokenStreamHelper(&self.tokens).hash(state); + } +} + +#[cfg(feature = "parsing")] +fn delimiter_span(delimiter: &MacroDelimiter) -> Span { + match delimiter { + MacroDelimiter::Paren(token) => token.span, + MacroDelimiter::Brace(token) => token.span, + MacroDelimiter::Bracket(token) => token.span, + } +} + +impl Macro { + /// Parse the tokens within the macro invocation's delimiters into a syntax + /// tree. + /// + /// This is equivalent to `syn::parse2::<T>(mac.tokens)` except that it + /// produces a more useful span when `tokens` is empty. + /// + /// # Example + /// + /// ``` + /// use syn::{parse_quote, Expr, ExprLit, Ident, Lit, LitStr, Macro, Token}; + /// use syn::ext::IdentExt; + /// use syn::parse::{Error, Parse, ParseStream, Result}; + /// use syn::punctuated::Punctuated; + /// + /// // The arguments expected by libcore's format_args macro, and as a + /// // result most other formatting and printing macros like println. + /// // + /// // println!("{} is {number:.prec$}", "x", prec=5, number=0.01) + /// struct FormatArgs { + /// format_string: Expr, + /// positional_args: Vec<Expr>, + /// named_args: Vec<(Ident, Expr)>, + /// } + /// + /// impl Parse for FormatArgs { + /// fn parse(input: ParseStream) -> Result<Self> { + /// let format_string: Expr; + /// let mut positional_args = Vec::new(); + /// let mut named_args = Vec::new(); + /// + /// format_string = input.parse()?; + /// while !input.is_empty() { + /// input.parse::<Token![,]>()?; + /// if input.is_empty() { + /// break; + /// } + /// if input.peek(Ident::peek_any) && input.peek2(Token![=]) { + /// while !input.is_empty() { + /// let name: Ident = input.call(Ident::parse_any)?; + /// input.parse::<Token![=]>()?; + /// let value: Expr = input.parse()?; + /// named_args.push((name, value)); + /// if input.is_empty() { + /// break; + /// } + /// input.parse::<Token![,]>()?; + /// } + /// break; + /// } + /// positional_args.push(input.parse()?); + /// } + /// + /// Ok(FormatArgs { + /// format_string, + /// positional_args, + /// named_args, + /// }) + /// } + /// } + /// + /// // Extract the first argument, the format string literal, from an + /// // invocation of a formatting or printing macro. + /// fn get_format_string(m: &Macro) -> Result<LitStr> { + /// let args: FormatArgs = m.parse_body()?; + /// match args.format_string { + /// Expr::Lit(ExprLit { lit: Lit::Str(lit), .. }) => Ok(lit), + /// other => { + /// // First argument was not a string literal expression. + /// // Maybe something like: println!(concat!(...), ...) + /// Err(Error::new_spanned(other, "format string must be a string literal")) + /// } + /// } + /// } + /// + /// fn main() { + /// let invocation = parse_quote! { + /// println!("{:?}", Instant::now()) + /// }; + /// let lit = get_format_string(&invocation).unwrap(); + /// assert_eq!(lit.value(), "{:?}"); + /// } + /// ``` + #[cfg(feature = "parsing")] + pub fn parse_body<T: Parse>(&self) -> Result<T> { + self.parse_body_with(T::parse) + } + + /// Parse the tokens within the macro invocation's delimiters using the + /// given parser. + #[cfg(feature = "parsing")] + pub fn parse_body_with<F: Parser>(&self, parser: F) -> Result<F::Output> { + // TODO: see if we can get a group.span_close() span in here as the + // scope, rather than the span of the whole group. + let scope = delimiter_span(&self.delimiter); + crate::parse::parse_scoped(parser, scope, self.tokens.clone()) + } +} + +#[cfg(feature = "parsing")] +pub fn parse_delimiter(input: ParseStream) -> Result<(MacroDelimiter, TokenStream)> { + input.step(|cursor| { + if let Some((TokenTree::Group(g), rest)) = cursor.token_tree() { + let span = g.span(); + let delimiter = match g.delimiter() { + Delimiter::Parenthesis => MacroDelimiter::Paren(Paren(span)), + Delimiter::Brace => MacroDelimiter::Brace(Brace(span)), + Delimiter::Bracket => MacroDelimiter::Bracket(Bracket(span)), + Delimiter::None => { + return Err(cursor.error("expected delimiter")); + } + }; + Ok(((delimiter, g.stream()), rest)) + } else { + Err(cursor.error("expected delimiter")) + } + }) +} + +#[cfg(feature = "parsing")] +pub mod parsing { + use super::*; + + use crate::parse::{Parse, ParseStream, Result}; + + impl Parse for Macro { + fn parse(input: ParseStream) -> Result<Self> { + let tokens; + Ok(Macro { + path: input.call(Path::parse_mod_style)?, + bang_token: input.parse()?, + delimiter: { + let (delimiter, content) = parse_delimiter(input)?; + tokens = content; + delimiter + }, + tokens, + }) + } + } +} + +#[cfg(feature = "printing")] +mod printing { + use super::*; + use proc_macro2::TokenStream; + use quote::ToTokens; + + impl ToTokens for Macro { + fn to_tokens(&self, tokens: &mut TokenStream) { + self.path.to_tokens(tokens); + self.bang_token.to_tokens(tokens); + match &self.delimiter { + MacroDelimiter::Paren(paren) => { + paren.surround(tokens, |tokens| self.tokens.to_tokens(tokens)); + } + MacroDelimiter::Brace(brace) => { + brace.surround(tokens, |tokens| self.tokens.to_tokens(tokens)); + } + MacroDelimiter::Bracket(bracket) => { + bracket.surround(tokens, |tokens| self.tokens.to_tokens(tokens)); + } + } + } + } +} |