From 3f31044d908fed9d158cb8d24716447d8bc5f45e Mon Sep 17 00:00:00 2001
From: LeSeulArtichaut <leseulartichaut@gmail.com>
Date: Sat, 22 May 2021 15:40:26 +0200
Subject: [PATCH] Handle typeck errors properly

---
 compiler/rustc_middle/src/query/mod.rs         | 2 +-
 compiler/rustc_mir_build/src/check_unsafety.rs | 5 +++++
 compiler/rustc_mir_build/src/thir/cx/mod.rs    | 3 +++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index f940cb62d9e2..9125be33c93d 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -220,7 +220,7 @@ rustc_queries! {
         desc { "checking if the crate is_panic_runtime" }
     }
 
-    /// Fetch the THIR for a given body.
+    /// Fetch the THIR for a given body. If typeck for that body failed, returns an empty `Thir`.
     query thir_body(key: ty::WithOptConstParam<LocalDefId>) -> (&'tcx Steal<thir::Thir<'tcx>>, thir::ExprId) {
         desc { |tcx| "building THIR for `{}`", tcx.def_path_str(key.did.to_def_id()) }
     }
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index d0d376bd3e3d..66fe5524ef4b 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -331,6 +331,11 @@ impl UnsafeOpKind {
 pub fn check_unsafety<'tcx>(tcx: TyCtxt<'tcx>, def: ty::WithOptConstParam<LocalDefId>) {
     let (thir, expr) = tcx.thir_body(def);
     let thir = &thir.borrow();
+    // If `thir` is empty, a type error occured, skip this body.
+    if thir.exprs.is_empty() {
+        return;
+    }
+
     let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
     let body_unsafety = tcx.hir().fn_sig_by_hir_id(hir_id).map_or(BodyUnsafety::Safe, |fn_sig| {
         if fn_sig.header.unsafety == hir::Unsafety::Unsafe {
diff --git a/compiler/rustc_mir_build/src/thir/cx/mod.rs b/compiler/rustc_mir_build/src/thir/cx/mod.rs
index f7f092b2037a..49ba71e3520d 100644
--- a/compiler/rustc_mir_build/src/thir/cx/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/mod.rs
@@ -23,6 +23,9 @@ crate fn thir_body<'tcx>(
     let hir = tcx.hir();
     let body = hir.body(hir.body_owned_by(hir.local_def_id_to_hir_id(owner_def.did)));
     let mut cx = Cx::new(tcx, owner_def);
+    if cx.typeck_results.tainted_by_errors.is_some() {
+        return (tcx.alloc_steal_thir(Thir::new()), ExprId::from_u32(0));
+    }
     let expr = cx.mirror_expr(&body.value);
     (tcx.alloc_steal_thir(cx.thir), expr)
 }