Add `tags.scm`

[hkmatsumoto]

Thanks for all the effort on tree-sitter! Excited to see a lot of features are implemented on syntax trees this parser outputs.

This PR has high hopes to help the realization of Code Navigation feature for Rust. The output of tree-sitter tags examples/ast.rs | head -n 30 is as follows:

Lifetime         | class        def (36, 11) - (36, 19) `pub struct Lifetime {`
fmt              | method       def (43, 7) - (43, 10) `fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {`
write            | call         ref (44, 8) - (44, 13) `write!(f, "lifetime({}: {})", self.id, pprust::lifetime_to_string(self))`
LifetimeDef      | class        def (50, 11) - (50, 22) `pub struct LifetimeDef {`
Path             | class        def (63, 11) - (63, 15) `pub struct Path {`
eq               | method       def (71, 7) - (71, 9) `fn eq(&self, string: &&'a str) -> bool {`
len              | call         ref (72, 22) - (72, 25) `self.segments.len() == 1 && self.segments[0].identifier.name == *string`
fmt              | method       def (77, 7) - (77, 10) `fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {`
write            | call         ref (78, 8) - (78, 13) `write!(f, "path({})", pprust::path_to_string(self))`
fmt              | method       def (83, 7) - (83, 10) `fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {`
write            | call         ref (84, 8) - (84, 13) `write!(f, "{}", pprust::path_to_string(self))`
Path             | implementation       ref (88, 5) - (88, 9) `impl Path {`
from_ident       | method       def (91, 11) - (91, 21) `pub fn from_ident(s: Span, identifier: Ident) -> Path {`
vec              | call         ref (94, 22) - (94, 25) `segments: vec![PathSegment::from_ident(identifier, s)],`
default_to_global        | method       def (100, 11) - (100, 28) `pub fn default_to_global(mut self) -> Path {`
is_global        | call         ref (101, 17) - (101, 26) `if !self.is_global() {`
is_path_segment_keyword  | call         ref (103, 45) - (103, 68) `if !::parse::token::Ident(ident).is_path_segment_keyword() ||`
name             | call         ref (104, 45) - (104, 49) `ident.name == keywords::Crate.name() {`
insert           | call         ref (105, 30) - (105, 36) `self.segments.insert(0, PathSegment::crate_root(self.span));`
is_global        | method       def (111, 11) - (111, 20) `pub fn is_global(&self) -> bool {`
is_empty         | call         ref (112, 23) - (112, 31) `!self.segments.is_empty() && self.segments[0].identifier.name == keywords::CrateRoot.name()`
name             | call         ref (112, 93) - (112, 97) `!self.segments.is_empty() && self.segments[0].identifier.name == keywords::CrateRoot.name()`
PathSegment      | class        def (120, 11) - (120, 22) `pub struct PathSegment {`
PathSegment      | implementation       ref (135, 5) - (135, 16) `impl PathSegment {`
from_ident       | method       def (136, 11) - (136, 21) `pub fn from_ident(ident: Ident, span: Span) -> Self {`
crate_root       | method       def (139, 11) - (139, 21) `pub fn crate_root(span: Span) -> Self {`
ctxt             | call         ref (141, 43) - (141, 47) `identifier: Ident { ctxt: span.ctxt(), ..keywords::CrateRoot.ident() },`
ident            | call         ref (141, 73) - (141, 78) `identifier: Ident { ctxt: span.ctxt(), ..keywords::CrateRoot.ident() },`
PathParameters   | class        def (152, 9) - (152, 23) `pub enum PathParameters {`
PathParameters   | implementation       ref (159, 5) - (159, 19) `impl PathParameters {`

[hkmatsumoto]

Thank you! Now that this is merged, what should we do to activate code navigation feature on GitHub for Rust, @patrickt ?

[patrickt]

@hkmatsumoto I’ve added it to our project board. I can’t make guarantees on timing, as we have to be careful adding new languages so as to keep our backend systems happy, but thank you very much for doing this! Also, if you’re amenable, there is now unit testing support for tags queries, if you’re looking for something to do while waiting.