pub struct Macro {
pub path: Path,
pub bang_token: Bang,
pub delimiter: MacroDelimiter,
pub tokens: TokenStream,
}
Expand description
A macro invocation: println!("{}", mac)
.
This type is available only if Syn is built with the "derive"
or "full"
feature.
Fields
path: Path
bang_token: Bang
delimiter: MacroDelimiter
tokens: TokenStream
Implementations
sourceimpl Macro
impl Macro
sourcepub fn parse_body<T: Parse>(&self) -> Result<T>
pub fn parse_body<T: Parse>(&self) -> Result<T>
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(), "{:?}");
}
sourcepub fn parse_body_with<F: Parser>(&self, parser: F) -> Result<F::Output>
pub fn parse_body_with<F: Parser>(&self, parser: F) -> Result<F::Output>
Parse the tokens within the macro invocation’s delimiters using the given parser.
Trait Implementations
sourceimpl ToTokens for Macro
impl ToTokens for Macro
sourcefn to_tokens(&self, tokens: &mut TokenStream)
fn to_tokens(&self, tokens: &mut TokenStream)
Write self
to the given TokenStream
. Read more
sourcefn to_token_stream(&self) -> TokenStream
fn to_token_stream(&self) -> TokenStream
Convert self
directly into a TokenStream
object. Read more
sourcefn into_token_stream(self) -> TokenStream
fn into_token_stream(self) -> TokenStream
Convert self
directly into a TokenStream
object. Read more
impl Eq for Macro
Auto Trait Implementations
impl RefUnwindSafe for Macro
impl !Send for Macro
impl !Sync for Macro
impl Unpin for Macro
impl UnwindSafe for Macro
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<T> Spanned for T where
T: Spanned + ?Sized,
impl<T> Spanned for T where
T: Spanned + ?Sized,
sourcefn span(&self) -> Span
fn span(&self) -> Span
Returns a Span
covering the complete contents of this syntax tree
node, or Span::call_site()
if this node is empty. Read more
sourceimpl<T> ToOwned for T where
T: Clone,
impl<T> ToOwned for T where
T: Clone,
type Owned = T
type Owned = T
The resulting type after obtaining ownership.
sourcefn clone_into(&self, target: &mut T)
fn clone_into(&self, target: &mut T)
toowned_clone_into
)Uses borrowed data to replace owned data, usually by cloning. Read more