74 lines
2.8 KiB
Rust
74 lines
2.8 KiB
Rust
use rustc_middle::mir::interpret::InterpResult;
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use rustc_middle::ty::{
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self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
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};
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use std::ops::ControlFlow;
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/// Checks whether a type contains generic parameters which require substitution.
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///
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/// In case it does, returns a `TooGeneric` const eval error. Note that due to polymorphization
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/// types may be "concrete enough" even though they still contain generic parameters in
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/// case these parameters are unused.
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pub(crate) fn ensure_monomorphic_enough<'tcx, T>(tcx: TyCtxt<'tcx>, ty: T) -> InterpResult<'tcx>
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where
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T: TypeVisitable<TyCtxt<'tcx>>,
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{
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debug!("ensure_monomorphic_enough: ty={:?}", ty);
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if !ty.has_param() {
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return Ok(());
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}
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struct FoundParam;
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struct UsedParamsNeedSubstVisitor<'tcx> {
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tcx: TyCtxt<'tcx>,
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}
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impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for UsedParamsNeedSubstVisitor<'tcx> {
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type BreakTy = FoundParam;
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fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
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if !ty.has_param() {
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return ControlFlow::Continue(());
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}
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match *ty.kind() {
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ty::Param(_) => ControlFlow::Break(FoundParam),
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ty::Closure(def_id, substs)
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| ty::Generator(def_id, substs, ..)
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| ty::FnDef(def_id, substs) => {
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let instance = ty::InstanceDef::Item(def_id);
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let unused_params = self.tcx.unused_generic_params(instance);
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for (index, subst) in substs.into_iter().enumerate() {
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let index = index
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.try_into()
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.expect("more generic parameters than can fit into a `u32`");
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// Only recurse when generic parameters in fns, closures and generators
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// are used and require substitution.
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// Just in case there are closures or generators within this subst,
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// recurse.
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if unused_params.is_used(index) && subst.has_param() {
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return subst.visit_with(self);
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}
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}
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ControlFlow::Continue(())
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}
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_ => ty.super_visit_with(self),
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}
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}
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fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
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match c.kind() {
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ty::ConstKind::Param(..) => ControlFlow::Break(FoundParam),
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_ => c.super_visit_with(self),
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}
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}
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}
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let mut vis = UsedParamsNeedSubstVisitor { tcx };
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if matches!(ty.visit_with(&mut vis), ControlFlow::Break(FoundParam)) {
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throw_inval!(TooGeneric);
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} else {
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Ok(())
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}
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}
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