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extern crate proc_macro;
use proc_macro::{token_stream::IntoIter, Delimiter, Group, Spacing, TokenStream, TokenTree};
use std::iter::FromIterator;
#[proc_macro]
pub fn tt_equal(item: TokenStream) -> TokenStream {
let (caller, lhs, rhs) = validate(item);
assert!(lhs.len() > 0);
assert!(rhs.len() > 0);
return_to_tt(
caller,
if lhs.len() == rhs.len() {
lhs.into_iter()
.zip(rhs.into_iter())
.all(|(lhs, rhs)| lhs.to_string().trim() == rhs.to_string().trim())
} else {
false
},
)
}
fn validate(item: TokenStream) -> (TokenTree, Vec<TokenTree>, Vec<TokenTree>) {
let mut iter = item.into_iter();
let caller = iter
.next()
.expect("'tt_equal' did not receive caller's tt bundle.");
let key = iter
.next()
.expect("'tt_equal' expects a key-value pair as input, but did not receive a key.");
if key.to_string().trim() != "input".to_string() {
panic!(
"'tt_equal' expects its input's key to be named 'input' but it was '{}'",
key.to_string().trim()
)
}
let separator = iter
.next()
.expect("'tt_equal' expects a key value pair as input but did not receive it.")
.to_string();
if separator != "=".to_string() {
panic!(
"'tt_equal' expects its input key-value pairs to be separated by a '=' \
but instead received '{}'",
separator
);
}
let value_group = iter
.next()
.expect("'tt_equal' expects a key-value pair as input but received no value.");
if iter.next().is_some() {
panic!("'tt_equal' expects only a key-value pair as input but received more.")
}
let mut unbracketed_group = expect_group(value_group, Delimiter::Bracket).into_iter();
let braced_group = unbracketed_group.next().expect(
"'tt_equal' expects its input value to be within '[{..}]' \
but the '{..}' was not given.",
);
if unbracketed_group.next().is_some() {
panic!(
"'tt_equal' expects its input value to be within '[{..}]' \
but it received additional tokens after the braces ('{..}')."
)
}
let mut clean_value = expect_group(braced_group, Delimiter::Brace).into_iter();
let lhs = get_next_joint_token(&mut clean_value)
.expect("'tt_equal' expects two token tree to compare but received none.");
let rhs = get_next_joint_token(&mut clean_value)
.expect("'tt_equal' expects two token tree to compare but received only one");
if let Some(x) = clean_value.next() {
panic!(
"'tt_equal' expects two token tree to compare but received more: '{:?} {:?} {:?}'",
lhs, rhs, x
)
}
(caller, lhs, rhs)
}
fn expect_group(tt: TokenTree, expected_delimiter: Delimiter) -> TokenStream {
if let TokenTree::Group(g) = tt {
if expected_delimiter == g.delimiter() {
g.stream()
} else {
panic!(
"'tt_equal' expects delimiter '{:?}' but got '{:?}'.",
expected_delimiter,
g.delimiter()
);
}
} else {
panic!(
"'tt_equal' expects a group of tokens inside {:?} but got '{:?}'",
expected_delimiter, tt
);
}
}
fn return_to_tt(caller: TokenTree, b: bool) -> TokenStream {
let return_call: TokenStream = "tt_call::tt_return!".parse().expect(
"'tt_equal' internal error 1. Please file a bug with the tt-equal crate maintainers.",
);
let return_value: TokenStream = format!("is_equal = [ {{ {} }} ]", b).parse().expect(
"'tt_equal' internal error 2. Please file a bug with the tt-equal crate maintainers.",
);
let mut return_body: Vec<_> = Vec::new();
return_body.push(caller);
return_body.extend(return_value);
let return_call_argument = TokenTree::from(Group::new(
Delimiter::Brace,
TokenStream::from_iter(return_body.into_iter()),
));
let mut result: Vec<TokenTree> = Vec::new();
result.extend(return_call);
result.push(return_call_argument);
return TokenStream::from_iter(result.into_iter());
}
fn get_next_joint_token(stream: &mut IntoIter) -> Option<Vec<TokenTree>> {
let first = stream.next()?;
if let TokenTree::Punct(last) = first {
let mut tokens = vec![last];
while let Spacing::Joint = tokens.last().unwrap().spacing() {
let next = stream.next().unwrap();
if let TokenTree::Punct(p) = next {
tokens.push(p);
} else {
panic!(
"'tt_equal' encountered a Punct token joint with \
a non-Punct token: '{:?} {:?}'",
tokens, next
);
}
}
Some(tokens.into_iter().map(|p| TokenTree::Punct(p)).collect())
} else {
Some(vec![first])
}
}