Add debug logging in hir_typeck::upvar

This aims to make each major part responsible for modifying the
precision be visible in the logs.

Author: meithecatte

compiler/rustc_hir_typeck/src/upvar.rs

@@ -761,6 +761,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ///       ],
     /// }
     /// ```
+    #[instrument(level = "debug", skip(self))]
     fn compute_min_captures(
         &self,
         closure_def_id: LocalDefId,
@@ -2029,6 +2030,7 @@ struct InferBorrowKind<'tcx> {
 }
 
 impl<'tcx> euv::Delegate<'tcx> for InferBorrowKind<'tcx> {
+    #[instrument(skip(self), level = "debug")]
     fn fake_read(
         &mut self,
         place_with_id: &PlaceWithHirId<'tcx>,
@@ -2119,6 +2121,7 @@ impl<'tcx> euv::Delegate<'tcx> for InferBorrowKind<'tcx> {
 }
 
 /// Rust doesn't permit moving fields out of a type that implements drop
+#[instrument(skip(fcx), ret, level = "debug")]
 fn restrict_precision_for_drop_types<'a, 'tcx>(
     fcx: &'a FnCtxt<'a, 'tcx>,
     mut place: Place<'tcx>,
@@ -2179,6 +2182,7 @@ fn restrict_precision_for_unsafe(
 /// - No unsafe block is required to capture `place`.
 ///
 /// Returns the truncated place and updated capture mode.
+#[instrument(ret, level = "debug")]
 fn restrict_capture_precision(
     place: Place<'_>,
     curr_mode: ty::UpvarCapture,
@@ -2208,6 +2212,7 @@ fn restrict_capture_precision(
 }
 
 /// Truncate deref of any reference.
+#[instrument(ret, level = "debug")]
 fn adjust_for_move_closure(
     mut place: Place<'_>,
     mut kind: ty::UpvarCapture,
@@ -2222,6 +2227,7 @@ fn adjust_for_move_closure(
 }
 
 /// Truncate deref of any reference.
+#[instrument(ret, level = "debug")]
 fn adjust_for_use_closure(
     mut place: Place<'_>,
     mut kind: ty::UpvarCapture,
@@ -2237,6 +2243,7 @@ fn adjust_for_use_closure(
 
 /// Adjust closure capture just that if taking ownership of data, only move data
 /// from enclosing stack frame.
+#[instrument(ret, level = "debug")]
 fn adjust_for_non_move_closure(
     mut place: Place<'_>,
     mut kind: ty::UpvarCapture,
@@ -2559,6 +2566,7 @@ fn determine_place_ancestry_relation<'tcx>(
 ///     // it is constrained to `'a`
 /// }
 /// ```
+#[instrument(ret, level = "debug")]
 fn truncate_capture_for_optimization(
     mut place: Place<'_>,
     mut curr_mode: ty::UpvarCapture,