From 93fcc395fa077f7341133e70e52e3659b4cc780b Mon Sep 17 00:00:00 2001
From: Tony Arcieri <bascule@gmail.com>
Date: Sat, 21 Jun 2025 10:34:13 -0600
Subject: [PATCH] der: remove `Reader::read_value`

This was added in #1877 but the real value of that PR was the automatic
`read_nested` on `DecodeValue` impls. `Reader::read_value` isn't
actually necessary for that at all.

It may be useful in the future if we introduce a BER reader that can
handle decoding constructed e.g. strings from indefinite length
encoding, but since we don't actually have anything like that yet,
removing this avoids some unnecessary duplication and API surface for
the `Reader`.
---
 der/src/asn1/internal_macros.rs |  6 +++---
 der/src/decode.rs               |  2 +-
 der/src/reader.rs               | 14 +-------------
 3 files changed, 5 insertions(+), 17 deletions(-)

diff --git a/der/src/asn1/internal_macros.rs b/der/src/asn1/internal_macros.rs
index ec1a48727..aeea1b2f6 100644
--- a/der/src/asn1/internal_macros.rs
+++ b/der/src/asn1/internal_macros.rs
@@ -151,8 +151,8 @@ macro_rules! impl_custom_class {
                     return Err(header.tag.non_canonical_error().into());
                 }
 
-                // read_value checks if header matches decoded length
-                let value = reader.read_value(header, |reader| {
+                // read_nested checks if header matches decoded length
+                let value = reader.read_nested(header.length, |reader| {
                     // Decode inner IMPLICIT value
                     T::decode_value(reader, header)
                 })?;
@@ -192,7 +192,7 @@ macro_rules! impl_custom_class {
                     Tag::$class_enum_name { number, .. } => Ok(Self {
                         tag_number: number,
                         tag_mode: TagMode::default(),
-                        value: reader.read_value(header, |reader| {
+                        value: reader.read_nested(header.length, |reader| {
                             // Decode inner tag-length-value of EXPLICIT
                             T::decode(reader)
                         })?,
diff --git a/der/src/decode.rs b/der/src/decode.rs
index a44a9687f..4129a0ec4 100644
--- a/der/src/decode.rs
+++ b/der/src/decode.rs
@@ -68,7 +68,7 @@ where
     fn decode<R: Reader<'a>>(reader: &mut R) -> Result<T, <T as DecodeValue<'a>>::Error> {
         let header = Header::decode(reader)?;
         header.tag.assert_eq(T::TAG)?;
-        reader.read_value(header, |r| T::decode_value(r, header))
+        reader.read_nested(header.length, |r| T::decode_value(r, header))
     }
 }
 
diff --git a/der/src/reader.rs b/der/src/reader.rs
index 0bbeeb566..9630d8dcc 100644
--- a/der/src/reader.rs
+++ b/der/src/reader.rs
@@ -32,18 +32,6 @@ pub trait Reader<'r>: Clone {
         E: From<Error>,
         F: FnOnce(&mut Self) -> Result<T, E>;
 
-    /// Read a value (i.e. the "V" part of a "TLV" field) using the provided header.
-    ///
-    /// This calls the provided function `f` with a nested reader created using
-    /// [`Reader::read_nested`].
-    fn read_value<T, F, E>(&mut self, header: Header, f: F) -> Result<T, E>
-    where
-        E: From<Error>,
-        F: FnOnce(&mut Self) -> Result<T, E>,
-    {
-        self.read_nested(header.length, f)
-    }
-
     /// Attempt to read data borrowed directly from the input as a slice,
     /// updating the internal cursor position.
     ///
@@ -204,7 +192,7 @@ pub trait Reader<'r>: Clone {
     {
         let header = Header::decode(self)?;
         header.tag.assert_eq(Tag::Sequence)?;
-        self.read_value(header, f)
+        self.read_nested(header.length, f)
     }
 
     /// Obtain a slice of bytes containing a complete TLV production suitable for parsing later.