Bail out on overly generic substitutions

[rust.git] / src / librustc_mir / interpret / eval_context.rs

diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs
index 9a76a36ef2293057d08793a0ba91bd69db0af64c..b2db0fea3d09a7afdb7ff1c85edebe080963e65c 100644 (file)
--- a/src/librustc_mir/interpret/eval_context.rs
+++ b/src/librustc_mir/interpret/eval_context.rs
@@ -1,3 +1,4 @@
+use std::cell::Cell;
 use std::fmt::Write;
 use std::mem;
 
@@ -42,7 +43,7 @@ pub struct EvalContext<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'a, 'mir, 'tcx>> {
     pub(crate) stack: Vec<Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>>,
 
     /// A cache for deduplicating vtables
-    pub(super) vtables: FxHashMap<(Ty<'tcx>, ty::PolyExistentialTraitRef<'tcx>), AllocId>,
+    pub(super) vtables: FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), AllocId>,
 }
 
 /// A stack frame.
@@ -76,6 +77,7 @@ pub struct Frame<'mir, 'tcx: 'mir, Tag=(), Extra=()> {
     /// `None` represents a local that is currently dead, while a live local
     /// can either directly contain `Scalar` or refer to some part of an `Allocation`.
     pub locals: IndexVec<mir::Local, LocalValue<Tag>>,
+    pub local_layouts: IndexVec<mir::Local, Cell<Option<TyLayout<'tcx>>>>,
 
     ////////////////////////////////////////////////////////////////////////////////
     // Current position within the function
@@ -214,11 +216,21 @@ pub(super) fn mir(&self) -> &'mir mir::Mir<'tcx> {
         self.frame().mir
     }
 
-    pub fn substs(&self) -> &'tcx Substs<'tcx> {
-        if let Some(frame) = self.stack.last() {
-            frame.instance.substs
-        } else {
-            Substs::empty()
+    pub(super) fn subst_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>(
+        &self,
+        substs: T,
+    ) -> EvalResult<'tcx, T> {
+        match self.stack.last() {
+            Some(frame) => Ok(self.tcx.subst_and_normalize_erasing_regions(
+                frame.instance.substs,
+                self.param_env,
+                &substs,
+            )),
+            None => if substs.needs_subst() {
+                err!(TooGeneric).into()
+            } else {
+                Ok(substs)
+            },
         }
     }
 
@@ -228,13 +240,9 @@ pub(super) fn resolve(
         substs: &'tcx Substs<'tcx>
     ) -> EvalResult<'tcx, ty::Instance<'tcx>> {
         trace!("resolve: {:?}, {:#?}", def_id, substs);
-        trace!("substs: {:#?}", self.substs());
         trace!("param_env: {:#?}", self.param_env);
-        let substs = self.tcx.subst_and_normalize_erasing_regions(
-            self.substs(),
-            self.param_env,
-            &substs,
-        );
+        let substs = self.subst_and_normalize_erasing_regions(substs)?;
+        trace!("substs: {:#?}", substs);
         ty::Instance::resolve(
             *self.tcx,
             self.param_env,
@@ -274,6 +282,20 @@ pub fn load_mir(
         }
     }
 
+    pub fn monomorphize_in_frame<T: TypeFoldable<'tcx> + Subst<'tcx>>(
+        &self,
+        t: T,
+    ) -> EvalResult<'tcx, T> {
+        match self.stack.last() {
+            Some(frame) => Ok(self.monomorphize(t, frame.instance.substs)),
+            None => if t.needs_subst() {
+                err!(TooGeneric).into()
+            } else {
+                Ok(t)
+            },
+        }
+    }
+
     pub fn monomorphize<T: TypeFoldable<'tcx> + Subst<'tcx>>(
         &self,
         t: T,
@@ -290,9 +312,15 @@ pub fn layout_of_local(
         frame: &Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>,
         local: mir::Local
     ) -> EvalResult<'tcx, TyLayout<'tcx>> {
-        let local_ty = frame.mir.local_decls[local].ty;
-        let local_ty = self.monomorphize(local_ty, frame.instance.substs);
-        self.layout_of(local_ty)
+        let cell = &frame.local_layouts[local];
+        if cell.get().is_none() {
+            let local_ty = frame.mir.local_decls[local].ty;
+            let local_ty = self.monomorphize(local_ty, frame.instance.substs);
+            let layout = self.layout_of(local_ty)?;
+            cell.set(Some(layout));
+        }
+
+        Ok(cell.get().unwrap())
     }
 
     pub fn str_to_immediate(&mut self, s: &str) -> EvalResult<'tcx, Immediate<M::PointerTag>> {
@@ -426,6 +454,7 @@ pub fn push_stack_frame(
             // empty local array, we fill it in below, after we are inside the stack frame and
             // all methods actually know about the frame
             locals: IndexVec::new(),
+            local_layouts: IndexVec::from_elem_n(Default::default(), mir.local_decls.len()),
             span,
             instance,
             stmt: 0,
@@ -464,11 +493,11 @@ pub fn push_stack_frame(
                 },
             }
             // Finally, properly initialize all those that still have the dummy value
-            for (local, decl) in locals.iter_mut().zip(mir.local_decls.iter()) {
+            for (idx, local) in locals.iter_enumerated_mut() {
                 match *local {
                     LocalValue::Live(_) => {
                         // This needs to be peoperly initialized.
-                        let layout = self.layout_of(self.monomorphize(decl.ty, instance.substs))?;
+                        let layout = self.layout_of_local(self.frame(), idx)?;
                         *local = LocalValue::Live(self.uninit_operand(layout)?);
                     }
                     LocalValue::Dead => {