1
- //! Transcraber takes a template, like `fn $ident() {}`, a set of bindings like
1
+ //! Transcriber takes a template, like `fn $ident() {}`, a set of bindings like
2
2
//! `$ident => foo`, interpolates variables in the template, to get `fn foo() {}`
3
3
4
4
use ra_syntax:: SmolStr ;
@@ -53,7 +53,8 @@ impl Bindings {
53
53
pub ( super ) fn transcribe ( template : & tt:: Subtree , bindings : & Bindings ) -> ExpandResult < tt:: Subtree > {
54
54
assert ! ( template. delimiter == None ) ;
55
55
let mut ctx = ExpandCtx { bindings : & bindings, nesting : Vec :: new ( ) } ;
56
- expand_subtree ( & mut ctx, template)
56
+ let mut arena: Vec < tt:: TokenTree > = Vec :: new ( ) ;
57
+ expand_subtree ( & mut ctx, template, & mut arena)
57
58
}
58
59
59
60
#[ derive( Debug ) ]
@@ -73,8 +74,13 @@ struct ExpandCtx<'a> {
73
74
nesting : Vec < NestingState > ,
74
75
}
75
76
76
- fn expand_subtree ( ctx : & mut ExpandCtx , template : & tt:: Subtree ) -> ExpandResult < tt:: Subtree > {
77
- let mut buf: Vec < tt:: TokenTree > = Vec :: new ( ) ;
77
+ fn expand_subtree (
78
+ ctx : & mut ExpandCtx ,
79
+ template : & tt:: Subtree ,
80
+ arena : & mut Vec < tt:: TokenTree > ,
81
+ ) -> ExpandResult < tt:: Subtree > {
82
+ // remember how many elements are in the arena now - when returning, we want to drain exactly how many elements we added. This way, the recursive uses of the arena get their own "view" of the arena, but will reuse the allocation
83
+ let start_elements = arena. len ( ) ;
78
84
let mut err = None ;
79
85
for op in parse_template ( template) {
80
86
let op = match op {
@@ -85,25 +91,27 @@ fn expand_subtree(ctx: &mut ExpandCtx, template: &tt::Subtree) -> ExpandResult<t
85
91
}
86
92
} ;
87
93
match op {
88
- Op :: TokenTree ( tt @ tt:: TokenTree :: Leaf ( ..) ) => buf . push ( tt. clone ( ) ) ,
94
+ Op :: TokenTree ( tt @ tt:: TokenTree :: Leaf ( ..) ) => arena . push ( tt. clone ( ) ) ,
89
95
Op :: TokenTree ( tt:: TokenTree :: Subtree ( tt) ) => {
90
- let ExpandResult ( tt, e) = expand_subtree ( ctx, tt) ;
96
+ let ExpandResult ( tt, e) = expand_subtree ( ctx, tt, arena ) ;
91
97
err = err. or ( e) ;
92
- buf . push ( tt. into ( ) ) ;
98
+ arena . push ( tt. into ( ) ) ;
93
99
}
94
100
Op :: Var { name, kind : _ } => {
95
101
let ExpandResult ( fragment, e) = expand_var ( ctx, name) ;
96
102
err = err. or ( e) ;
97
- push_fragment ( & mut buf , fragment) ;
103
+ push_fragment ( arena , fragment) ;
98
104
}
99
105
Op :: Repeat { subtree, kind, separator } => {
100
- let ExpandResult ( fragment, e) = expand_repeat ( ctx, subtree, kind, separator) ;
106
+ let ExpandResult ( fragment, e) = expand_repeat ( ctx, subtree, kind, separator, arena ) ;
101
107
err = err. or ( e) ;
102
- push_fragment ( & mut buf , fragment)
108
+ push_fragment ( arena , fragment)
103
109
}
104
110
}
105
111
}
106
- ExpandResult ( tt:: Subtree { delimiter : template. delimiter , token_trees : buf } , err)
112
+ // drain the elements added in this instance of expand_subtree
113
+ let tts = arena. drain ( start_elements..arena. len ( ) ) . collect ( ) ;
114
+ ExpandResult ( tt:: Subtree { delimiter : template. delimiter , token_trees : tts } , err)
107
115
}
108
116
109
117
fn expand_var ( ctx : & mut ExpandCtx , v : & SmolStr ) -> ExpandResult < Fragment > {
@@ -155,6 +163,7 @@ fn expand_repeat(
155
163
template : & tt:: Subtree ,
156
164
kind : RepeatKind ,
157
165
separator : Option < Separator > ,
166
+ arena : & mut Vec < tt:: TokenTree > ,
158
167
) -> ExpandResult < Fragment > {
159
168
let mut buf: Vec < tt:: TokenTree > = Vec :: new ( ) ;
160
169
ctx. nesting . push ( NestingState { idx : 0 , at_end : false , hit : false } ) ;
@@ -165,7 +174,7 @@ fn expand_repeat(
165
174
let mut counter = 0 ;
166
175
167
176
loop {
168
- let ExpandResult ( mut t, e) = expand_subtree ( ctx, template) ;
177
+ let ExpandResult ( mut t, e) = expand_subtree ( ctx, template, arena ) ;
169
178
let nesting_state = ctx. nesting . last_mut ( ) . unwrap ( ) ;
170
179
if nesting_state. at_end || !nesting_state. hit {
171
180
break ;
0 commit comments