ICEs should print the top of the query stack

compiler/rustc_driver/src/lib.rs

@@ -1215,9 +1215,9 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str) {
     // If backtraces are enabled, also print the query stack
     let backtrace = env::var_os("RUST_BACKTRACE").map(|x| &x != "0").unwrap_or(false);
 
-    if backtrace {
-        TyCtxt::try_print_query_stack(&handler);
-    }
+    let num_frames = if backtrace { None } else { Some(2) };
+
+    TyCtxt::try_print_query_stack(&handler, num_frames);
 
     #[cfg(windows)]
     unsafe {

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

@@ -124,7 +124,7 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    pub fn try_print_query_stack(handler: &Handler) {
+    pub fn try_print_query_stack(handler: &Handler, num_frames: Option<usize>) {
         eprintln!("query stack during panic:");
 
         // Be careful reyling on global state here: this code is called from
@@ -138,6 +138,9 @@ impl<'tcx> TyCtxt<'tcx> {
                 let mut i = 0;
 
                 while let Some(query) = current_query {
+                    if num_frames == Some(i) {
+                        break;
+                    }
                     let query_info =
                         if let Some(info) = query_map.as_ref().and_then(|map| map.get(&query)) {
                             info
@@ -163,7 +166,11 @@ impl<'tcx> TyCtxt<'tcx> {
             }
         });
 
-        eprintln!("end of query stack");
+        if num_frames != None {
+            eprintln!("we're just showing a limited slice of the query stack");
+        } else {
+            eprintln!("end of query stack");
+        }
     }
 }
 

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

@@ -0,0 +1,17 @@
+thread 'rustc' panicked at 'assertion failed: rows.iter().all(|r| r.len() == v.len())', compiler/rustc_mir_build/src/thir/pattern/_match.rs:LL:CC
+note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+
+error: internal compiler error: unexpected panic
+
+note: the compiler unexpectedly panicked. this is a bug.
+
+note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md
+
+note: rustc VERSION running on TARGET
+
+note: compiler flags: FLAGS
+
+query stack during panic:
+#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.rs

@@ -9,6 +9,9 @@
 // normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
 // normalize-stderr-test "note: compiler flags.*\n\n" -> ""
 // normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
+// normalize-stderr-test "query stack during panic:\n" -> ""
+// normalize-stderr-test "we're just showing a limited slice of the query stack\n" -> ""
+// normalize-stderr-test "end of query stack\n" -> ""
 
 #[macro_use]
 extern crate invalid_punct_ident;

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

@@ -1,5 +1,5 @@
 error: proc macro panicked
-  --> $DIR/invalid-punct-ident-1.rs:16:1
+  --> $DIR/invalid-punct-ident-1.rs:19:1
    |
 LL | invalid_punct!();
    | ^^^^^^^^^^^^^^^^^

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

@@ -9,6 +9,9 @@
 // normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
 // normalize-stderr-test "note: compiler flags.*\n\n" -> ""
 // normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
+// normalize-stderr-test "query stack during panic:\n" -> ""
+// normalize-stderr-test "we're just showing a limited slice of the query stack\n" -> ""
+// normalize-stderr-test "end of query stack\n" -> ""
 
 #[macro_use]
 extern crate invalid_punct_ident;

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

@@ -1,5 +1,5 @@
 error: proc macro panicked
-  --> $DIR/invalid-punct-ident-2.rs:16:1
+  --> $DIR/invalid-punct-ident-2.rs:19:1
    |
 LL | invalid_ident!();
    | ^^^^^^^^^^^^^^^^^

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

@@ -9,6 +9,9 @@
 // normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
 // normalize-stderr-test "note: compiler flags.*\n\n" -> ""
 // normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
+// normalize-stderr-test "query stack during panic:\n" -> ""
+// normalize-stderr-test "we're just showing a limited slice of the query stack\n" -> ""
+// normalize-stderr-test "end of query stack\n" -> ""
 
 #[macro_use]
 extern crate invalid_punct_ident;

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

@@ -1,5 +1,5 @@
 error: proc macro panicked
-  --> $DIR/invalid-punct-ident-3.rs:16:1
+  --> $DIR/invalid-punct-ident-3.rs:19:1
    |
 LL | invalid_raw_ident!();
    | ^^^^^^^^^^^^^^^^^^^^^

src/test/ui/proc-macro/load-panic-backtrace.rs

@@ -10,6 +10,9 @@
 // normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
 // normalize-stderr-test "note: compiler flags.*\n\n" -> ""
 // normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
+// normalize-stderr-test "query stack during panic:\n" -> ""
+// normalize-stderr-test "we're just showing a limited slice of the query stack\n" -> ""
+// normalize-stderr-test "end of query stack\n" -> ""
 
 #[macro_use]
 extern crate test_macros;

src/test/ui/proc-macro/load-panic-backtrace.stderr

@@ -1,6 +1,6 @@
 at 'panic-derive', $DIR/auxiliary/test-macros.rs:43:5
 error: proc-macro derive panicked
-  --> $DIR/load-panic-backtrace.rs:17:10
+  --> $DIR/load-panic-backtrace.rs:20:10
    |
 LL | #[derive(Panic)]
    |          ^^^^^

src/tools/clippy/src/driver.rs

@@ -277,9 +277,9 @@ fn report_clippy_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str) {
     // If backtraces are enabled, also print the query stack
     let backtrace = env::var_os("RUST_BACKTRACE").map_or(false, |x| &x != "0");
 
-    if backtrace {
-        TyCtxt::try_print_query_stack(&handler);
-    }
+    let num_frames = if backtrace { None } else { Some(2) };
+
+    TyCtxt::try_print_query_stack(&handler, num_frames);
 }
 
 fn toolchain_path(home: Option<String>, toolchain: Option<String>) -> Option<PathBuf> {

src/tools/clippy/tests/ui/custom_ice_message.stderr

@@ -9,3 +9,5 @@ note: we would appreciate a bug report: https://github.com/rust-lang/rust-clippy
 
 note: Clippy version: foo
 
+query stack during panic:
+we're just showing a limited slice of the query stack