add comments

2 files changed, 7 insertions, 0 deletions

diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
index 4ad5d8443b2..d77fb1cc91e 100644
--- a/compiler/rustc_middle/src/ty/consts.rs
+++ b/compiler/rustc_middle/src/ty/consts.rs
@@ -222,6 +222,8 @@ impl<'tcx> Const<'tcx> {
     }
 
     /// Attempts to convert to a value.
+    ///
+    /// Note that this does not evaluate the constant.
     pub fn try_to_value(self) -> Option<ty::Value<'tcx>> {
         match self.kind() {
             ty::ConstKind::Value(cv) => Some(cv),
@@ -229,6 +231,10 @@ impl<'tcx> Const<'tcx> {
         }
     }
 
+    /// Convenience method to extract the value of a usize constant,
+    /// useful to get the length of an array type.
+    ///
+    /// Note that this does not evaluate the constant.
     #[inline]
     pub fn try_to_target_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> {
         self.try_to_value()?.try_to_target_usize(tcx)
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 19a39b3a29e..018fcc66aee 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1785,6 +1785,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         Ok(())
     }
 
+    // FIXME(valtrees): Accept `ty::Value` instead of `Ty` and `ty::ValTree` separately.
     fn pretty_print_const_valtree(
         &mut self,
         valtree: ty::ValTree<'tcx>,