Add more trace info.

Author: jumbatm

src/librustc_lint/builtin.rs

@@ -47,7 +47,7 @@ use rustc_trait_selection::traits::misc::can_type_implement_copy;
 
 use crate::nonstandard_style::{method_context, MethodLateContext};
 
-use log::debug;
+use log::{debug, trace};
 use std::fmt::Write;
 
 // hardwired lints from librustc
@@ -1181,11 +1181,14 @@ fn check_const(cx: &LateContext<'_, '_>, body_id: hir::BodyId) {
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedBrokenConst {
     fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
+        trace!("UnusedBrokenConst: check_item(_, _, {:?}", it);
         match it.kind {
             hir::ItemKind::Const(_, body_id) => {
+                trace!("UnusedBrokenConst: checking {:?}", body_id);
                 check_const(cx, body_id);
             }
             hir::ItemKind::Static(_, _, body_id) => {
+                trace!("UnusedBrokenConst: checking {:?}", body_id);
                 check_const(cx, body_id);
             }
             _ => {}

src/librustc_mir/const_eval/eval_queries.rs

@@ -181,6 +181,8 @@ fn validate_and_turn_into_const<'tcx>(
     let val = (|| {
         let mplace = ecx.raw_const_to_mplace(constant)?;
 
+        debug!("validate_and_turn_into_const: mplace = {:?}", mplace);
+
         // FIXME do not validate promoteds until a decision on
         // https://github.com/rust-lang/rust/issues/67465 is made
         if cid.promoted.is_none() {
@@ -209,6 +211,7 @@ fn validate_and_turn_into_const<'tcx>(
     })();
 
     val.map_err(|error| {
+        trace!("Validation failed: {:?}", error);
         let err = error_to_const_error(&ecx, error);
         match err.struct_error(ecx.tcx, "it is undefined behavior to use this value", |mut diag| {
             diag.note(note_on_undefined_behavior_error());
@@ -251,7 +254,10 @@ pub fn const_eval_validated_provider<'tcx>(
         });
     }
 
-    tcx.const_eval_raw(key).and_then(|val| validate_and_turn_into_const(tcx, val, key))
+    tcx.const_eval_raw(key).and_then(|val| {
+        trace!("const_eval_raw succeeded. val.alloc_id = {:?}. val.ty = {:?}", val.alloc_id, val.ty);
+        validate_and_turn_into_const(tcx, val, key)
+    })
 }
 
 pub fn const_eval_raw_provider<'tcx>(
@@ -271,7 +277,7 @@ pub fn const_eval_raw_provider<'tcx>(
         key.param_env.reveal = Reveal::UserFacing;
         match tcx.const_eval_raw(key) {
             // try again with reveal all as requested
-            Err(ErrorHandled::TooGeneric) => {}
+            Err(ErrorHandled::TooGeneric) => { trace!("const_eval_raw: retrying with RevealAll"); }
             // deduplicate calls
             other => return other,
         }

src/librustc_mir/interpret/eval_context.rs

@@ -208,7 +208,11 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> LayoutOf for InterpCx<'mir, 'tcx, M> {
     fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyLayout {
         self.tcx
             .layout_of(self.param_env.and(ty))
-            .map_err(|layout| err_inval!(Layout(layout)).into())
+            .map_err(|layout| {
+                let result = err_inval!(Layout(layout)).into();
+                trace!("layout_of: returning error: {:?}", result);
+                result
+            })
     }
 }
 

src/librustc_mir/interpret/place.rs

@@ -1134,6 +1134,7 @@ where
     ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
         // This must be an allocation in `tcx`
         assert!(self.tcx.alloc_map.lock().get(raw.alloc_id).is_some());
+        trace!("raw_const_to_mplace: raw.ty = {:?}", raw.ty);
         let ptr = self.tag_global_base_pointer(Pointer::from(raw.alloc_id));
         let layout = self.layout_of(raw.ty)?;
         Ok(MPlaceTy::from_aligned_ptr(ptr, layout))