1- use rustc_middle:: ty:: { self , AdtSizedConstraint , Ty , TyCtxt } ;
1+ use rustc_data_structures:: fx:: FxHashSet ;
2+ use rustc_errors:: { pluralize, struct_span_err, Applicability , MultiSpan } ;
3+ use rustc_hir as hir;
4+ use rustc_hir:: def:: DefKind ;
5+ use rustc_middle:: ty:: Representability ;
6+ use rustc_middle:: ty:: { self , AdtSizedConstraint , DefIdTree , Ty , TyCtxt } ;
7+ use rustc_query_system:: query:: QueryInfo ;
28use rustc_query_system:: Value ;
9+ use rustc_span:: def_id:: LocalDefId ;
10+ use rustc_span:: Span ;
11+
12+ use std:: fmt:: Write ;
313
414impl < ' tcx > Value < TyCtxt < ' tcx > > for Ty < ' _ > {
5- fn from_cycle_error ( tcx : TyCtxt < ' tcx > ) -> Self {
15+ fn from_cycle_error ( tcx : TyCtxt < ' tcx > , _ : & [ QueryInfo ] ) -> Self {
616 // SAFETY: This is never called when `Self` is not `Ty<'tcx>`.
717 // FIXME: Represent the above fact in the trait system somehow.
818 unsafe { std:: mem:: transmute :: < Ty < ' tcx > , Ty < ' _ > > ( tcx. ty_error ( ) ) }
919 }
1020}
1121
1222impl < ' tcx > Value < TyCtxt < ' tcx > > for ty:: SymbolName < ' _ > {
13- fn from_cycle_error ( tcx : TyCtxt < ' tcx > ) -> Self {
23+ fn from_cycle_error ( tcx : TyCtxt < ' tcx > , _ : & [ QueryInfo ] ) -> Self {
1424 // SAFETY: This is never called when `Self` is not `SymbolName<'tcx>`.
1525 // FIXME: Represent the above fact in the trait system somehow.
1626 unsafe {
@@ -22,7 +32,7 @@ impl<'tcx> Value<TyCtxt<'tcx>> for ty::SymbolName<'_> {
2232}
2333
2434impl < ' tcx > Value < TyCtxt < ' tcx > > for AdtSizedConstraint < ' _ > {
25- fn from_cycle_error ( tcx : TyCtxt < ' tcx > ) -> Self {
35+ fn from_cycle_error ( tcx : TyCtxt < ' tcx > , _ : & [ QueryInfo ] ) -> Self {
2636 // SAFETY: This is never called when `Self` is not `AdtSizedConstraint<'tcx>`.
2737 // FIXME: Represent the above fact in the trait system somehow.
2838 unsafe {
@@ -34,7 +44,7 @@ impl<'tcx> Value<TyCtxt<'tcx>> for AdtSizedConstraint<'_> {
3444}
3545
3646impl < ' tcx > Value < TyCtxt < ' tcx > > for ty:: Binder < ' _ , ty:: FnSig < ' _ > > {
37- fn from_cycle_error ( tcx : TyCtxt < ' tcx > ) -> Self {
47+ fn from_cycle_error ( tcx : TyCtxt < ' tcx > , _ : & [ QueryInfo ] ) -> Self {
3848 let err = tcx. ty_error ( ) ;
3949 // FIXME(compiler-errors): It would be nice if we could get the
4050 // query key, so we could at least generate a fn signature that
@@ -52,3 +62,153 @@ impl<'tcx> Value<TyCtxt<'tcx>> for ty::Binder<'_, ty::FnSig<'_>> {
5262 unsafe { std:: mem:: transmute :: < ty:: PolyFnSig < ' tcx > , ty:: Binder < ' _ , ty:: FnSig < ' _ > > > ( fn_sig) }
5363 }
5464}
65+
66+ impl < ' tcx > Value < TyCtxt < ' tcx > > for Representability {
67+ fn from_cycle_error ( tcx : TyCtxt < ' tcx > , cycle : & [ QueryInfo ] ) -> Self {
68+ let mut item_and_field_ids = Vec :: new ( ) ;
69+ let mut representable_ids = FxHashSet :: default ( ) ;
70+ for info in cycle {
71+ if info. query . name == "representability"
72+ && let Some ( field_id) = info. query . def_id
73+ && let Some ( field_id) = field_id. as_local ( )
74+ && let Some ( DefKind :: Field ) = info. query . def_kind
75+ {
76+ let parent_id = tcx. parent ( field_id. to_def_id ( ) ) ;
77+ let item_id = match tcx. def_kind ( parent_id) {
78+ DefKind :: Variant => tcx. parent ( parent_id) ,
79+ _ => parent_id,
80+ } ;
81+ item_and_field_ids. push ( ( item_id. expect_local ( ) , field_id) ) ;
82+ }
83+ }
84+ for info in cycle {
85+ if info. query . name == "representability_adt_ty"
86+ && let Some ( def_id) = info. query . ty_adt_id
87+ && let Some ( def_id) = def_id. as_local ( )
88+ && !item_and_field_ids. iter ( ) . any ( |& ( id, _) | id == def_id)
89+ {
90+ representable_ids. insert ( def_id) ;
91+ }
92+ }
93+ recursive_type_error ( tcx, item_and_field_ids, & representable_ids) ;
94+ Representability :: Infinite
95+ }
96+ }
97+
98+ // item_and_field_ids should form a cycle where each field contains the
99+ // type in the next element in the list
100+ pub fn recursive_type_error (
101+ tcx : TyCtxt < ' _ > ,
102+ mut item_and_field_ids : Vec < ( LocalDefId , LocalDefId ) > ,
103+ representable_ids : & FxHashSet < LocalDefId > ,
104+ ) {
105+ const ITEM_LIMIT : usize = 5 ;
106+
107+ // Rotate the cycle so that the item with the lowest span is first
108+ let start_index = item_and_field_ids
109+ . iter ( )
110+ . enumerate ( )
111+ . min_by_key ( |& ( _, & ( id, _) ) | tcx. def_span ( id) )
112+ . unwrap ( )
113+ . 0 ;
114+ item_and_field_ids. rotate_left ( start_index) ;
115+
116+ let cycle_len = item_and_field_ids. len ( ) ;
117+ let show_cycle_len = cycle_len. min ( ITEM_LIMIT ) ;
118+
119+ let mut err_span = MultiSpan :: from_spans (
120+ item_and_field_ids[ ..show_cycle_len]
121+ . iter ( )
122+ . map ( |( id, _) | tcx. def_span ( id. to_def_id ( ) ) )
123+ . collect ( ) ,
124+ ) ;
125+ let mut suggestion = Vec :: with_capacity ( show_cycle_len * 2 ) ;
126+ for i in 0 ..show_cycle_len {
127+ let ( _, field_id) = item_and_field_ids[ i] ;
128+ let ( next_item_id, _) = item_and_field_ids[ ( i + 1 ) % cycle_len] ;
129+ // Find the span(s) that contain the next item in the cycle
130+ let hir_id = tcx. hir ( ) . local_def_id_to_hir_id ( field_id) ;
131+ let hir:: Node :: Field ( field) = tcx. hir ( ) . get ( hir_id) else { bug ! ( "expected field" ) } ;
132+ let mut found = Vec :: new ( ) ;
133+ find_item_ty_spans ( tcx, field. ty , next_item_id, & mut found, representable_ids) ;
134+
135+ // Couldn't find the type. Maybe it's behind a type alias?
136+ // In any case, we'll just suggest boxing the whole field.
137+ if found. is_empty ( ) {
138+ found. push ( field. ty . span ) ;
139+ }
140+
141+ for span in found {
142+ err_span. push_span_label ( span, "recursive without indirection" ) ;
143+ // FIXME(compiler-errors): This suggestion might be erroneous if Box is shadowed
144+ suggestion. push ( ( span. shrink_to_lo ( ) , "Box<" . to_string ( ) ) ) ;
145+ suggestion. push ( ( span. shrink_to_hi ( ) , ">" . to_string ( ) ) ) ;
146+ }
147+ }
148+ let items_list = {
149+ let mut s = String :: new ( ) ;
150+ for ( i, ( item_id, _) ) in item_and_field_ids. iter ( ) . enumerate ( ) {
151+ let path = tcx. def_path_str ( item_id. to_def_id ( ) ) ;
152+ write ! ( & mut s, "`{path}`" ) . unwrap ( ) ;
153+ if i == ( ITEM_LIMIT - 1 ) && cycle_len > ITEM_LIMIT {
154+ write ! ( & mut s, " and {} more" , cycle_len - 5 ) . unwrap ( ) ;
155+ break ;
156+ }
157+ if cycle_len > 1 && i < cycle_len - 2 {
158+ s. push_str ( ", " ) ;
159+ } else if cycle_len > 1 && i == cycle_len - 2 {
160+ s. push_str ( " and " )
161+ }
162+ }
163+ s
164+ } ;
165+ let mut err = struct_span_err ! (
166+ tcx. sess,
167+ err_span,
168+ E0072 ,
169+ "recursive type{} {} {} infinite size" ,
170+ pluralize!( cycle_len) ,
171+ items_list,
172+ pluralize!( "has" , cycle_len) ,
173+ ) ;
174+ err. multipart_suggestion (
175+ "insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle" ,
176+ suggestion,
177+ Applicability :: HasPlaceholders ,
178+ ) ;
179+ err. emit ( ) ;
180+ }
181+
182+ fn find_item_ty_spans (
183+ tcx : TyCtxt < ' _ > ,
184+ ty : & hir:: Ty < ' _ > ,
185+ needle : LocalDefId ,
186+ spans : & mut Vec < Span > ,
187+ seen_representable : & FxHashSet < LocalDefId > ,
188+ ) {
189+ match ty. kind {
190+ hir:: TyKind :: Path ( hir:: QPath :: Resolved ( _, path) ) => {
191+ if let Some ( def_id) = path. res . opt_def_id ( ) {
192+ let check_params = def_id. as_local ( ) . map_or ( true , |def_id| {
193+ if def_id == needle {
194+ spans. push ( ty. span ) ;
195+ }
196+ seen_representable. contains ( & def_id)
197+ } ) ;
198+ if check_params && let Some ( args) = path. segments . last ( ) . unwrap ( ) . args {
199+ let params_in_repr = tcx. params_in_repr ( def_id) ;
200+ for ( i, arg) in args. args . iter ( ) . enumerate ( ) {
201+ if let hir:: GenericArg :: Type ( ty) = arg && params_in_repr. contains ( i as u32 ) {
202+ find_item_ty_spans ( tcx, ty, needle, spans, seen_representable) ;
203+ }
204+ }
205+ }
206+ }
207+ }
208+ hir:: TyKind :: Array ( ty, _) => find_item_ty_spans ( tcx, ty, needle, spans, seen_representable) ,
209+ hir:: TyKind :: Tup ( tys) => {
210+ tys. iter ( ) . for_each ( |ty| find_item_ty_spans ( tcx, ty, needle, spans, seen_representable) )
211+ }
212+ _ => { }
213+ }
214+ }
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