show a message when we are showing limited slice of query stack

compiler/rustc_middle/src/ty/query/plumbing.rs

@@ -127,6 +127,9 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn try_print_query_stack(handler: &Handler, num_frames: Option<usize>) {
         eprintln!("query stack during panic:");
 
+        if num_frames != None {
+            eprintln!("we're just showing a limited slice of the query stack");
+        }
         // Be careful reyling on global state here: this code is called from
         // a panic hook, which means that the global `Handler` may be in a weird
         // state if it was responsible for triggering the panic.

src/test/ui/pattern/const-pat-ice.stderr

@@ -12,6 +12,7 @@ note: rustc VERSION running on TARGET
 note: compiler flags: FLAGS
 
 query stack during panic:
+we're just showing a limited slice of the query stack
 #0 [check_match] match-checking `main`
 #1 [analysis] running analysis passes on this crate
 we're just showing a limited slice of the query stack

src/test/ui/proc-macro/invalid-punct-ident-1.stderr

@@ -1,4 +1,5 @@
 query stack during panic:
+we're just showing a limited slice of the query stack
 end of query stack
 error: proc macro panicked
   --> $DIR/invalid-punct-ident-1.rs:19:1

src/test/ui/proc-macro/invalid-punct-ident-2.stderr

@@ -1,4 +1,5 @@
 query stack during panic:
+we're just showing a limited slice of the query stack
 end of query stack
 error: proc macro panicked
   --> $DIR/invalid-punct-ident-2.rs:19:1

src/test/ui/proc-macro/invalid-punct-ident-3.stderr

@@ -1,4 +1,5 @@
 query stack during panic:
+we're just showing a limited slice of the query stack
 end of query stack
 error: proc macro panicked
   --> $DIR/invalid-punct-ident-3.rs:19:1