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3dfed10e XL |
1 | use rustc_middle::mir::interpret::InterpResult; |
2 | use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitor}; | |
3 | use std::convert::TryInto; | |
4 | ||
5 | /// Returns `true` if a used generic parameter requires substitution. | |
6 | crate fn ensure_monomorphic_enough<'tcx, T>(tcx: TyCtxt<'tcx>, ty: T) -> InterpResult<'tcx> | |
7 | where | |
8 | T: TypeFoldable<'tcx>, | |
9 | { | |
10 | debug!("ensure_monomorphic_enough: ty={:?}", ty); | |
11 | if !ty.needs_subst() { | |
12 | return Ok(()); | |
13 | } | |
14 | ||
15 | struct UsedParamsNeedSubstVisitor<'tcx> { | |
16 | tcx: TyCtxt<'tcx>, | |
17 | }; | |
18 | ||
19 | impl<'tcx> TypeVisitor<'tcx> for UsedParamsNeedSubstVisitor<'tcx> { | |
20 | fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> bool { | |
21 | if !c.needs_subst() { | |
22 | return false; | |
23 | } | |
24 | ||
25 | match c.val { | |
26 | ty::ConstKind::Param(..) => true, | |
27 | _ => c.super_visit_with(self), | |
28 | } | |
29 | } | |
30 | ||
31 | fn visit_ty(&mut self, ty: Ty<'tcx>) -> bool { | |
32 | if !ty.needs_subst() { | |
33 | return false; | |
34 | } | |
35 | ||
36 | match ty.kind { | |
37 | ty::Param(_) => true, | |
38 | ty::Closure(def_id, substs) | |
39 | | ty::Generator(def_id, substs, ..) | |
40 | | ty::FnDef(def_id, substs) => { | |
41 | let unused_params = self.tcx.unused_generic_params(def_id); | |
42 | for (index, subst) in substs.into_iter().enumerate() { | |
43 | let index = index | |
44 | .try_into() | |
45 | .expect("more generic parameters than can fit into a `u32`"); | |
46 | let is_used = | |
47 | unused_params.contains(index).map(|unused| !unused).unwrap_or(true); | |
48 | // Only recurse when generic parameters in fns, closures and generators | |
49 | // are used and require substitution. | |
50 | match (is_used, subst.needs_subst()) { | |
51 | // Just in case there are closures or generators within this subst, | |
52 | // recurse. | |
53 | (true, true) if subst.super_visit_with(self) => { | |
54 | // Only return when we find a parameter so the remaining substs | |
55 | // are not skipped. | |
56 | return true; | |
57 | } | |
58 | // Confirm that polymorphization replaced the parameter with | |
59 | // `ty::Param`/`ty::ConstKind::Param`. | |
60 | (false, true) if cfg!(debug_assertions) => match subst.unpack() { | |
61 | ty::subst::GenericArgKind::Type(ty) => { | |
62 | assert!(matches!(ty.kind, ty::Param(_))) | |
63 | } | |
64 | ty::subst::GenericArgKind::Const(ct) => { | |
65 | assert!(matches!(ct.val, ty::ConstKind::Param(_))) | |
66 | } | |
67 | ty::subst::GenericArgKind::Lifetime(..) => (), | |
68 | }, | |
69 | _ => {} | |
70 | } | |
71 | } | |
72 | false | |
73 | } | |
74 | _ => ty.super_visit_with(self), | |
75 | } | |
76 | } | |
77 | } | |
78 | ||
79 | let mut vis = UsedParamsNeedSubstVisitor { tcx }; | |
80 | if ty.visit_with(&mut vis) { | |
81 | throw_inval!(TooGeneric); | |
82 | } else { | |
83 | Ok(()) | |
84 | } | |
85 | } |