add debug logs

src/librustc/hir/lowering.rs

@@ -322,7 +322,7 @@ enum ParenthesizedGenericArgs {
 /// `resolve_lifetime` module. Often we "fallthrough" to that code by generating
 /// an "elided" or "underscore" lifetime name. In the future, we probably want to move
 /// everything into HIR lowering.
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Debug)]
 enum AnonymousLifetimeMode {
     /// For **Modern** cases, create a new anonymous region parameter
     /// and reference that.
@@ -715,10 +715,16 @@ impl<'a> LoweringContext<'a> {
         anonymous_lifetime_mode: AnonymousLifetimeMode,
         op: impl FnOnce(&mut Self) -> R,
     ) -> R {
+        debug!(
+            "with_anonymous_lifetime_mode(anonymous_lifetime_mode={:?})",
+            anonymous_lifetime_mode,
+        );
         let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
         self.anonymous_lifetime_mode = anonymous_lifetime_mode;
         let result = op(self);
         self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
+        debug!("with_anonymous_lifetime_mode: restoring anonymous_lifetime_mode={:?}",
+               old_anonymous_lifetime_mode);
         result
     }
 
@@ -1355,6 +1361,13 @@ impl<'a> LoweringContext<'a> {
         opaque_ty_node_id: NodeId,
         lower_bounds: impl FnOnce(&mut LoweringContext<'_>) -> hir::GenericBounds,
     ) -> hir::TyKind {
+        debug!(
+            "lower_opaque_impl_trait(fn_def_id={:?}, opaque_ty_node_id={:?}, span={:?})",
+            fn_def_id,
+            opaque_ty_node_id,
+            span,
+        );
+
         // Make sure we know that some funky desugaring has been going on here.
         // This is a first: there is code in other places like for loop
         // desugaring that explicitly states that we don't want to track that.
@@ -1382,6 +1395,14 @@ impl<'a> LoweringContext<'a> {
             &hir_bounds,
         );
 
+        debug!(
+            "lower_opaque_impl_trait: lifetimes={:#?}", lifetimes,
+        );
+
+        debug!(
+            "lower_opaque_impl_trait: lifetime_defs={:#?}", lifetime_defs,
+        );
+
         self.with_hir_id_owner(opaque_ty_node_id, |lctx| {
             let opaque_ty_item = hir::OpaqueTy {
                 generics: hir::Generics {
@@ -1397,7 +1418,7 @@ impl<'a> LoweringContext<'a> {
                 origin: hir::OpaqueTyOrigin::FnReturn,
             };
 
-            trace!("exist ty from impl trait def-index: {:#?}", opaque_ty_def_index);
+            trace!("lower_opaque_impl_trait: {:#?}", opaque_ty_def_index);
             let opaque_ty_id = lctx.generate_opaque_type(
                 opaque_ty_node_id,
                 opaque_ty_item,
@@ -1445,6 +1466,13 @@ impl<'a> LoweringContext<'a> {
         parent_index: DefIndex,
         bounds: &hir::GenericBounds,
     ) -> (HirVec<hir::GenericArg>, HirVec<hir::GenericParam>) {
+        debug!(
+            "lifetimes_from_impl_trait_bounds(opaque_ty_id={:?}, \
+             parent_index={:?}, \
+             bounds={:#?})",
+            opaque_ty_id, parent_index, bounds,
+        );
+
         // This visitor walks over `impl Trait` bounds and creates defs for all lifetimes that
         // appear in the bounds, excluding lifetimes that are created within the bounds.
         // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
@@ -2182,6 +2210,14 @@ impl<'a> LoweringContext<'a> {
         fn_def_id: DefId,
         opaque_ty_node_id: NodeId,
     ) -> hir::FunctionRetTy {
+        debug!(
+            "lower_async_fn_ret_ty(\
+             output={:?}, \
+             fn_def_id={:?}, \
+             opaque_ty_node_id={:?})",
+            output, fn_def_id, opaque_ty_node_id,
+        );
+
         let span = output.span();
 
         let opaque_ty_span = self.mark_span_with_reason(
@@ -2264,6 +2300,8 @@ impl<'a> LoweringContext<'a> {
                 ),
             );
 
+            debug!("lower_async_fn_ret_ty: future_bound={:#?}", future_bound);
+
             // Calculate all the lifetimes that should be captured
             // by the opaque type. This should include all in-scope
             // lifetime parameters, including those defined in-band.

src/librustc/infer/opaque_types/mod.rs

@@ -1108,6 +1108,7 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
         // Use the same type variable if the exact same opaque type appears more
         // than once in the return type (e.g., if it's passed to a type alias).
         if let Some(opaque_defn) = self.opaque_types.get(&def_id) {
+            debug!("instantiate_opaque_types: returning concrete ty {:?}", opaque_defn.concrete_ty);
             return opaque_defn.concrete_ty;
         }
         let span = tcx.def_span(def_id);

src/librustc/middle/resolve_lifetime.rs

@@ -585,6 +585,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 self.is_in_fn_syntax = was_in_fn_syntax;
             }
             hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
+                debug!("visit_ty: TraitObject(bounds={:?}, lifetime={:?})", bounds, lifetime);
                 for bound in bounds {
                     self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
                 }
@@ -897,6 +898,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
     }
 
     fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
+        debug!("visit_lifetime(lifetime_ref={:?})", lifetime_ref);
         if lifetime_ref.is_elided() {
             self.resolve_elided_lifetimes(vec![lifetime_ref]);
             return;
@@ -2347,6 +2349,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
     }
 
     fn resolve_elided_lifetimes(&mut self, lifetime_refs: Vec<&'tcx hir::Lifetime>) {
+        debug!("resolve_elided_lifetimes(lifetime_refs={:?})", lifetime_refs);
+
         if lifetime_refs.is_empty() {
             return;
         }
@@ -2539,6 +2543,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
     }
 
     fn resolve_object_lifetime_default(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
+        debug!("resolve_object_lifetime_default(lifetime_ref={:?})", lifetime_ref);
         let mut late_depth = 0;
         let mut scope = self.scope;
         let lifetime = loop {