From 4fb260bb32a2da7d7ea63b759eef77072a95614b Mon Sep 17 00:00:00 2001
From: Gary Guo <gary@garyguo.net>
Date: Sat, 4 Jul 2020 18:41:30 +0100
Subject: [PATCH] Guard against non-monomorphized type_id intrinsic call

---
 src/librustc_mir/interpret/intrinsics.rs | 12 +++++++++--
 src/test/ui/consts/issue-73976.rs        | 26 ++++++++++++++++++++++++
 src/test/ui/consts/issue-73976.stderr    | 14 +++++++++++++
 3 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 src/test/ui/consts/issue-73976.rs
 create mode 100644 src/test/ui/consts/issue-73976.stderr

diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs
index 5836fc9c95a..29549041d25 100644
--- a/src/librustc_mir/interpret/intrinsics.rs
+++ b/src/librustc_mir/interpret/intrinsics.rs
@@ -12,7 +12,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty;
 use rustc_middle::ty::subst::SubstsRef;
-use rustc_middle::ty::{Ty, TyCtxt};
+use rustc_middle::ty::{Ty, TyCtxt, TypeFoldable};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_target::abi::{Abi, LayoutOf as _, Primitive, Size};
 
@@ -54,6 +54,9 @@ crate fn eval_nullary_intrinsic<'tcx>(
     let name = tcx.item_name(def_id);
     Ok(match name {
         sym::type_name => {
+            if tp_ty.needs_subst() {
+                throw_inval!(TooGeneric);
+            }
             let alloc = type_name::alloc_type_name(tcx, tp_ty);
             ConstValue::Slice { data: alloc, start: 0, end: alloc.len() }
         }
@@ -68,7 +71,12 @@ crate fn eval_nullary_intrinsic<'tcx>(
             };
             ConstValue::from_machine_usize(n, &tcx)
         }
-        sym::type_id => ConstValue::from_u64(tcx.type_id_hash(tp_ty)),
+        sym::type_id => {
+            if tp_ty.needs_subst() {
+                throw_inval!(TooGeneric);
+            }
+            ConstValue::from_u64(tcx.type_id_hash(tp_ty))
+        }
         sym::variant_count => {
             if let ty::Adt(ref adt, _) = tp_ty.kind {
                 ConstValue::from_machine_usize(adt.variants.len() as u64, &tcx)
diff --git a/src/test/ui/consts/issue-73976.rs b/src/test/ui/consts/issue-73976.rs
new file mode 100644
index 00000000000..ef141791c2c
--- /dev/null
+++ b/src/test/ui/consts/issue-73976.rs
@@ -0,0 +1,26 @@
+// This test is from #73976. We previously did not check if a type is monomorphized
+// before calculating its type id, which leads to the bizzare behaviour below that
+// TypeId of a generic type does not match itself.
+//
+// This test case should either run-pass or be rejected at compile time.
+// Currently we just disallow this usage and require pattern is monomorphic.
+
+#![feature(const_type_id)]
+
+use std::any::TypeId;
+
+pub struct GetTypeId<T>(T);
+
+impl<T: 'static> GetTypeId<T> {
+    pub const VALUE: TypeId = TypeId::of::<T>();
+}
+
+const fn check_type_id<T: 'static>() -> bool {
+    matches!(GetTypeId::<T>::VALUE, GetTypeId::<T>::VALUE)
+    //~^ ERROR could not evaluate constant pattern
+    //~| ERROR could not evaluate constant pattern
+}
+
+fn main() {
+    assert!(check_type_id::<usize>());
+}
diff --git a/src/test/ui/consts/issue-73976.stderr b/src/test/ui/consts/issue-73976.stderr
new file mode 100644
index 00000000000..dbb7690b849
--- /dev/null
+++ b/src/test/ui/consts/issue-73976.stderr
@@ -0,0 +1,14 @@
+error: could not evaluate constant pattern
+  --> $DIR/issue-73976.rs:19:37
+   |
+LL |     matches!(GetTypeId::<T>::VALUE, GetTypeId::<T>::VALUE)
+   |                                     ^^^^^^^^^^^^^^^^^^^^^
+
+error: could not evaluate constant pattern
+  --> $DIR/issue-73976.rs:19:37
+   |
+LL |     matches!(GetTypeId::<T>::VALUE, GetTypeId::<T>::VALUE)
+   |                                     ^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+