Skip dead code checks on items that failed typeck

Author: oli-obk

compiler/rustc_passes/src/dead.rs

@@ -423,8 +423,11 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
 
 impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
     fn visit_nested_body(&mut self, body: hir::BodyId) {
-        let old_maybe_typeck_results =
-            self.maybe_typeck_results.replace(self.tcx.typeck_body(body));
+        let typeck_results = self.tcx.typeck_body(body);
+        if typeck_results.tainted_by_errors.is_some() {
+            return;
+        }
+        let old_maybe_typeck_results = self.maybe_typeck_results.replace(typeck_results);
         let body = self.tcx.hir().body(body);
         self.visit_body(body);
         self.maybe_typeck_results = old_maybe_typeck_results;

tests/ui/consts/const-eval/infinite_loop.rs

@@ -1,12 +1,20 @@
+//! This test tests two things at once:
+//! 1. we error if a const evaluation hits the deny-by-default lint limit
+//! 2. we do not ICE on invalid follow-up code
+
+// compile-flags: -Z tiny-const-eval-limit
+
 fn main() {
     // Tests the Collatz conjecture with an incorrect base case (0 instead of 1).
     // The value of `n` will loop indefinitely (4 - 2 - 1 - 4).
-    let _ = [(); {
+    let s = [(); {
         let mut n = 113383; // #20 in https://oeis.org/A006884
         while n != 0 {
             //~^ ERROR is taking a long time
             n = if n % 2 == 0 { n / 2 } else { 3 * n + 1 };
         }
         n
     }];
+
+    s.nonexistent_method();
 }

tests/ui/consts/const-eval/infinite_loop.stderr

@@ -1,5 +1,5 @@
 error: constant evaluation is taking a long time
-  --> $DIR/infinite_loop.rs:6:9
+  --> $DIR/infinite_loop.rs:12:9
    |
 LL | /         while n != 0 {
 LL | |
@@ -10,9 +10,9 @@ LL | |         }
    = note: this lint makes sure the compiler doesn't get stuck due to infinite loops in const eval.
            If your compilation actually takes a long time, you can safely allow the lint.
 help: the constant being evaluated
-  --> $DIR/infinite_loop.rs:4:18
+  --> $DIR/infinite_loop.rs:10:18
    |
-LL |       let _ = [(); {
+LL |       let s = [(); {
    |  __________________^
 LL | |         let mut n = 113383; // #20 in https://oeis.org/A006884
 LL | |         while n != 0 {