Made the varint decode_signed module report the correct errors

src/error.rs

@@ -105,6 +105,23 @@ pub enum DecodeError {
     },
 }
 
+impl DecodeError {
+    /// If the current error is `InvalidIntegerType`, change the `expected` and
+    /// `found` values from `Ux` to `Ix`. This is needed to have correct error
+    /// reporting in src/varint/decode_signed.rs since this calls
+    /// src/varint/decode_unsigned.rs and needs to correct the `expected` and
+    /// `found` types.
+    pub(crate) fn change_integer_type_to_signed(self) -> DecodeError {
+        match self {
+            Self::InvalidIntegerType { expected, found } => Self::InvalidIntegerType {
+                expected: expected.into_signed(),
+                found: found.into_signed(),
+            },
+            other => other,
+        }
+    }
+}
+
 /// Integer types. Used by [DecodeError]. These types have no purpose other than being shown in errors.
 #[non_exhaustive]
 #[derive(Debug)]
@@ -124,3 +141,20 @@ pub enum IntegerType {
     I128,
     Isize,
 }
+
+impl IntegerType {
+    /// Change the `Ux` value to the associated `Ix` value.
+    /// Returns the old value if `self` is already `Ix`.
+    pub(crate) fn into_signed(self) -> Self {
+        match self {
+            Self::U8 => Self::I8,
+            Self::U16 => Self::I16,
+            Self::U32 => Self::I32,
+            Self::U64 => Self::I64,
+            Self::U128 => Self::I128,
+            Self::Usize => Self::Isize,
+
+            other => other,
+        }
+    }
+}

src/varint/decode_signed.rs

@@ -1,7 +1,12 @@
-use crate::{config::Endian, de::read::Reader, error::DecodeError};
+use crate::{
+    config::Endian,
+    de::read::Reader,
+    error::{DecodeError, IntegerType},
+};
 
 pub fn varint_decode_i16<R: Reader>(read: &mut R, endian: Endian) -> Result<i16, DecodeError> {
-    let n = super::varint_decode_u16(read, endian)?;
+    let n = super::varint_decode_u16(read, endian)
+        .map_err(DecodeError::change_integer_type_to_signed)?;
     Ok(if n % 2 == 0 {
         // positive number
         (n / 2) as _
@@ -17,7 +22,8 @@ pub fn varint_decode_i16<R: Reader>(read: &mut R, endian: Endian) -> Result<i16,
 }
 
 pub fn varint_decode_i32<R: Reader>(read: &mut R, endian: Endian) -> Result<i32, DecodeError> {
-    let n = super::varint_decode_u32(read, endian)?;
+    let n = super::varint_decode_u32(read, endian)
+        .map_err(DecodeError::change_integer_type_to_signed)?;
     Ok(if n % 2 == 0 {
         // positive number
         (n / 2) as _
@@ -33,7 +39,8 @@ pub fn varint_decode_i32<R: Reader>(read: &mut R, endian: Endian) -> Result<i32,
 }
 
 pub fn varint_decode_i64<R: Reader>(read: &mut R, endian: Endian) -> Result<i64, DecodeError> {
-    let n = super::varint_decode_u64(read, endian)?;
+    let n = super::varint_decode_u64(read, endian)
+        .map_err(DecodeError::change_integer_type_to_signed)?;
     Ok(if n % 2 == 0 {
         // positive number
         (n / 2) as _
@@ -49,7 +56,8 @@ pub fn varint_decode_i64<R: Reader>(read: &mut R, endian: Endian) -> Result<i64,
 }
 
 pub fn varint_decode_i128<R: Reader>(read: &mut R, endian: Endian) -> Result<i128, DecodeError> {
-    let n = super::varint_decode_u128(read, endian)?;
+    let n = super::varint_decode_u128(read, endian)
+        .map_err(DecodeError::change_integer_type_to_signed)?;
     Ok(if n % 2 == 0 {
         // positive number
         (n / 2) as _
@@ -65,5 +73,14 @@ pub fn varint_decode_i128<R: Reader>(read: &mut R, endian: Endian) -> Result<i12
 }
 
 pub fn varint_decode_isize<R: Reader>(read: &mut R, endian: Endian) -> Result<isize, DecodeError> {
-    varint_decode_i64(read, endian).map(|v| v as isize)
+    match varint_decode_i64(read, endian) {
+        Ok(val) => Ok(val as isize),
+        Err(DecodeError::InvalidIntegerType { found, .. }) => {
+            Err(DecodeError::InvalidIntegerType {
+                expected: IntegerType::Isize,
+                found: found.into_signed(),
+            })
+        }
+        Err(e) => Err(e),
+    }
 }