New upstream version 1.57.0+dfsg1

[rustc.git] / compiler / rustc_const_eval / src / interpret / util.rs

diff --git a/compiler/rustc_const_eval/src/interpret/util.rs b/compiler/rustc_const_eval/src/interpret/util.rs
new file mode 100644 (file)
index 0000000..a16388d
--- /dev/null
+++ b/compiler/rustc_const_eval/src/interpret/util.rs
@@ -0,0 +1,85 @@
+use rustc_middle::mir::interpret::InterpResult;
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitor};
+use std::convert::TryInto;
+use std::ops::ControlFlow;
+
+/// Returns `true` if a used generic parameter requires substitution.
+crate fn ensure_monomorphic_enough<'tcx, T>(tcx: TyCtxt<'tcx>, ty: T) -> InterpResult<'tcx>
+where
+    T: TypeFoldable<'tcx>,
+{
+    debug!("ensure_monomorphic_enough: ty={:?}", ty);
+    if !ty.potentially_needs_subst() {
+        return Ok(());
+    }
+
+    struct FoundParam;
+    struct UsedParamsNeedSubstVisitor<'tcx> {
+        tcx: TyCtxt<'tcx>,
+    }
+
+    impl<'tcx> TypeVisitor<'tcx> for UsedParamsNeedSubstVisitor<'tcx> {
+        type BreakTy = FoundParam;
+
+        fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
+            Some(self.tcx)
+        }
+
+        fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
+            if !ty.potentially_needs_subst() {
+                return ControlFlow::CONTINUE;
+            }
+
+            match *ty.kind() {
+                ty::Param(_) => ControlFlow::Break(FoundParam),
+                ty::Closure(def_id, substs)
+                | ty::Generator(def_id, substs, ..)
+                | ty::FnDef(def_id, substs) => {
+                    let instance = ty::InstanceDef::Item(ty::WithOptConstParam::unknown(def_id));
+                    let unused_params = self.tcx.unused_generic_params(instance);
+                    for (index, subst) in substs.into_iter().enumerate() {
+                        let index = index
+                            .try_into()
+                            .expect("more generic parameters than can fit into a `u32`");
+                        let is_used = unused_params.contains(index).map_or(true, |unused| !unused);
+                        // Only recurse when generic parameters in fns, closures and generators
+                        // are used and require substitution.
+                        match (is_used, subst.definitely_needs_subst(self.tcx)) {
+                            // Just in case there are closures or generators within this subst,
+                            // recurse.
+                            (true, true) => return subst.super_visit_with(self),
+                            // Confirm that polymorphization replaced the parameter with
+                            // `ty::Param`/`ty::ConstKind::Param`.
+                            (false, true) if cfg!(debug_assertions) => match subst.unpack() {
+                                ty::subst::GenericArgKind::Type(ty) => {
+                                    assert!(matches!(ty.kind(), ty::Param(_)))
+                                }
+                                ty::subst::GenericArgKind::Const(ct) => {
+                                    assert!(matches!(ct.val, ty::ConstKind::Param(_)))
+                                }
+                                ty::subst::GenericArgKind::Lifetime(..) => (),
+                            },
+                            _ => {}
+                        }
+                    }
+                    ControlFlow::CONTINUE
+                }
+                _ => ty.super_visit_with(self),
+            }
+        }
+
+        fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
+            match c.val {
+                ty::ConstKind::Param(..) => ControlFlow::Break(FoundParam),
+                _ => c.super_visit_with(self),
+            }
+        }
+    }
+
+    let mut vis = UsedParamsNeedSubstVisitor { tcx };
+    if matches!(ty.visit_with(&mut vis), ControlFlow::Break(FoundParam)) {
+        throw_inval!(TooGeneric);
+    } else {
+        Ok(())
+    }
+}