Stop hiding const eval limit in external macros

compiler/rustc_lint_defs/src/builtin.rs

@@ -3464,7 +3464,8 @@
     /// out an update in your own time.
     pub LONG_RUNNING_CONST_EVAL,
     Deny,
-    "detects long const eval operations"
+    "detects long const eval operations",
+    report_in_external_macro
 }
 
 declare_lint! {

tests/ui/consts/timeout.rs

@@ -0,0 +1,25 @@
+//! This test checks that external macros don't hide
+//! the const eval timeout lint and then subsequently
+//! ICE.
+
+// compile-flags: --crate-type=lib -Ztiny-const-eval-limit
+// error-pattern: constant evaluation is taking a long time
+
+static ROOK_ATTACKS_TABLE: () = {
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+    0_u64.count_ones();
+};

tests/ui/consts/timeout.stderr

@@ -0,0 +1,15 @@
+error: constant evaluation is taking a long time
+  --> $SRC_DIR/core/src/num/mod.rs:LL:COL
+   |
+   = 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/timeout.rs:8:1
+   |
+LL | static ROOK_ATTACKS_TABLE: () = {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: `#[deny(long_running_const_eval)]` on by default
+   = note: this error originates in the macro `uint_impl` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to previous error
+