@@ -44,6 +44,7 @@ extern crate tracing;
4444
4545use crate :: errors:: { AssocTyParentheses , AssocTyParenthesesSub , MisplacedImplTrait } ;
4646
47+ use rustc_arena:: declare_arena;
4748use rustc_ast:: ptr:: P ;
4849use rustc_ast:: visit;
4950use rustc_ast:: { self as ast, * } ;
@@ -95,6 +96,13 @@ struct LoweringContext<'a, 'hir> {
9596 /// Used to allocate HIR nodes.
9697 arena : & ' hir hir:: Arena < ' hir > ,
9798
99+ /// Used to allocate temporary AST nodes for use during lowering.
100+ /// This allows us to create "fake" AST -- these nodes can sometimes
101+ /// be allocated on the stack, but other times we need them to live longer
102+ /// than the current stack frame, so they can be collected into vectors
103+ /// and things like that.
104+ ast_arena : & ' a Arena < ' static > ,
105+
98106 /// Bodies inside the owner being lowered.
99107 bodies : Vec < ( hir:: ItemLocalId , & ' hir hir:: Body < ' hir > ) > ,
100108 /// Attributes inside the owner being lowered.
@@ -140,6 +148,15 @@ struct LoweringContext<'a, 'hir> {
140148 generics_def_id_map : Vec < FxHashMap < LocalDefId , LocalDefId > > ,
141149}
142150
151+ declare_arena ! ( [
152+ [ ] tys: rustc_ast:: Ty ,
153+ [ ] aba: rustc_ast:: AngleBracketedArgs ,
154+ [ ] ptr: rustc_ast:: PolyTraitRef ,
155+ // This _marker field is needed because `declare_arena` creates `Arena<'tcx>` and we need to
156+ // use `'tcx`. If we don't have this we get a compile error.
157+ [ ] _marker: std:: marker:: PhantomData <& ' tcx ( ) >,
158+ ] ) ;
159+
143160trait ResolverAstLoweringExt {
144161 fn legacy_const_generic_args ( & self , expr : & Expr ) -> Option < Vec < usize > > ;
145162 fn get_partial_res ( & self , id : NodeId ) -> Option < PartialRes > ;
@@ -401,10 +418,13 @@ pub fn lower_to_hir<'hir>(tcx: TyCtxt<'hir>, (): ()) -> hir::Crate<'hir> {
401418 tcx. definitions_untracked ( ) . def_index_count ( ) ,
402419 ) ;
403420
421+ let ast_arena = Arena :: default ( ) ;
422+
404423 for def_id in ast_index. indices ( ) {
405424 item:: ItemLowerer {
406425 tcx,
407426 resolver : & mut resolver,
427+ ast_arena : & ast_arena,
408428 ast_index : & ast_index,
409429 owners : & mut owners,
410430 }
@@ -974,12 +994,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
974994 }
975995 GenericArgs :: Parenthesized ( ref data) => {
976996 self . emit_bad_parenthesized_trait_in_assoc_ty ( data) ;
977- self . lower_angle_bracketed_parameter_data (
978- & data. as_angle_bracketed_args ( ) ,
979- ParamMode :: Explicit ,
980- itctx,
981- )
982- . 0
997+ let aba = self . ast_arena . aba . alloc ( data. as_angle_bracketed_args ( ) ) ;
998+ self . lower_angle_bracketed_parameter_data ( aba, ParamMode :: Explicit , itctx) . 0
983999 }
9841000 } ;
9851001 gen_args_ctor. into_generic_args ( self )
@@ -1048,15 +1064,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
10481064
10491065 self . with_dyn_type_scope ( false , |this| {
10501066 let node_id = this. next_node_id ( ) ;
1051- let ty = this. lower_ty (
1052- & Ty {
1053- id : node_id,
1054- kind : TyKind :: ImplTrait ( impl_trait_node_id, bounds. clone ( ) ) ,
1055- span : this. lower_span ( constraint. span ) ,
1056- tokens : None ,
1057- } ,
1058- itctx,
1059- ) ;
1067+ let ty = this. ast_arena . tys . alloc ( Ty {
1068+ id : node_id,
1069+ kind : TyKind :: ImplTrait ( impl_trait_node_id, bounds. clone ( ) ) ,
1070+ span : this. lower_span ( constraint. span ) ,
1071+ tokens : None ,
1072+ } ) ;
1073+ let ty = this. lower_ty ( ty, itctx) ;
10601074
10611075 hir:: TypeBindingKind :: Equality { term : ty. into ( ) }
10621076 } )
@@ -1192,12 +1206,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
11921206 && let Res :: Def ( DefKind :: Trait | DefKind :: TraitAlias , _) = partial_res. base_res ( )
11931207 {
11941208 let ( bounds, lifetime_bound) = self . with_dyn_type_scope ( true , |this| {
1209+ let poly_trait_ref = this. ast_arena . ptr . alloc ( PolyTraitRef {
1210+ bound_generic_params : vec ! [ ] ,
1211+ trait_ref : TraitRef { path : path. clone ( ) , ref_id : t. id } ,
1212+ span : t. span
1213+ } ) ;
11951214 let bound = this. lower_poly_trait_ref (
1196- & PolyTraitRef {
1197- bound_generic_params : vec ! [ ] ,
1198- trait_ref : TraitRef { path : path. clone ( ) , ref_id : t. id } ,
1199- span : t. span
1200- } ,
1215+ poly_trait_ref,
12011216 itctx,
12021217 ) ;
12031218 let bounds = this. arena . alloc_from_iter ( [ bound] ) ;
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