curve: Expand lints (#530)

Adds a lints section to the top of lib.rs with the following:

    #![warn(
        clippy::unwrap_used,
        missing_docs,
        rust_2018_idioms,
        unused_lifetimes,
        unused_qualifications
    )]

`warn` is used instead of `deny` to prevent the lints from firing during
local development, however we already configure `-D warnings` in CI so
if any lint fails on checked-in code, it will cause a CI failure.

This commit also fixes or explicitly allows any current violations of
these lints. The main ones were:

- `clippy::unwrap_used`: replaces usages of `unwrap` with `expect`
- `rust_2018_idioms`: no implicit lifetimes, which were present on
  usages of `core::fmt::Formatter`

curve25519-dalek/src/backend/serial/curve_models/mod.rs

@@ -527,7 +527,7 @@ impl<'a> Neg for &'a AffineNielsPoint {
 // ------------------------------------------------------------------------
 
 impl Debug for ProjectivePoint {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(
             f,
             "ProjectivePoint{{\n\tX: {:?},\n\tY: {:?},\n\tZ: {:?}\n}}",
@@ -537,7 +537,7 @@ impl Debug for ProjectivePoint {
 }
 
 impl Debug for CompletedPoint {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(
             f,
             "CompletedPoint{{\n\tX: {:?},\n\tY: {:?},\n\tZ: {:?},\n\tT: {:?}\n}}",
@@ -547,7 +547,7 @@ impl Debug for CompletedPoint {
 }
 
 impl Debug for AffineNielsPoint {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(
             f,
             "AffineNielsPoint{{\n\ty_plus_x: {:?},\n\ty_minus_x: {:?},\n\txy2d: {:?}\n}}",
@@ -557,7 +557,7 @@ impl Debug for AffineNielsPoint {
 }
 
 impl Debug for ProjectiveNielsPoint {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "ProjectiveNielsPoint{{\n\tY_plus_X: {:?},\n\tY_minus_X: {:?},\n\tZ: {:?},\n\tT2d: {:?}\n}}",
                &self.Y_plus_X, &self.Y_minus_X, &self.Z, &self.T2d)
     }

curve25519-dalek/src/backend/serial/fiat_u32/field.rs

@@ -58,7 +58,7 @@ use fiat_crypto::curve25519_32::*;
 pub struct FieldElement2625(pub(crate) [u32; 10]);
 
 impl Debug for FieldElement2625 {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "FieldElement2625({:?})", &self.0[..])
     }
 }

curve25519-dalek/src/backend/serial/fiat_u64/field.rs

@@ -47,7 +47,7 @@ use fiat_crypto::curve25519_64::*;
 pub struct FieldElement51(pub(crate) [u64; 5]);
 
 impl Debug for FieldElement51 {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "FieldElement51({:?})", &self.0[..])
     }
 }

curve25519-dalek/src/backend/serial/scalar_mul/pippenger.rs

@@ -154,8 +154,7 @@ impl VartimeMultiscalarMul for Pippenger {
         });
 
         // Take the high column as an initial value to avoid wasting time doubling the identity element in `fold()`.
-        // `unwrap()` always succeeds because we know we have more than zero digits.
-        let hi_column = columns.next().unwrap();
+        let hi_column = columns.next().expect("should have more than zero digits");
 
         Some(columns.fold(hi_column, |total, p| total.mul_by_pow_2(w as u32) + p))
     }

curve25519-dalek/src/backend/serial/u32/field.rs

@@ -54,7 +54,7 @@ use zeroize::Zeroize;
 pub struct FieldElement2625(pub(crate) [u32; 10]);
 
 impl Debug for FieldElement2625 {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "FieldElement2625({:?})", &self.0[..])
     }
 }

curve25519-dalek/src/backend/serial/u32/scalar.rs

@@ -24,7 +24,7 @@ use crate::constants;
 pub struct Scalar29(pub [u32; 9]);
 
 impl Debug for Scalar29 {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "Scalar29: {:?}", &self.0[..])
     }
 }

curve25519-dalek/src/backend/serial/u64/field.rs

@@ -43,7 +43,7 @@ use zeroize::Zeroize;
 pub struct FieldElement51(pub(crate) [u64; 5]);
 
 impl Debug for FieldElement51 {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "FieldElement51({:?})", &self.0[..])
     }
 }

curve25519-dalek/src/backend/serial/u64/scalar.rs

@@ -25,7 +25,7 @@ use crate::constants;
 pub struct Scalar52(pub [u64; 5]);
 
 impl Debug for Scalar52 {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "Scalar52: {:?}", &self.0[..])
     }
 }

curve25519-dalek/src/backend/vector/avx2/edwards.rs

@@ -240,7 +240,7 @@ impl ConditionallySelectable for CachedPoint {
 }
 
 #[unsafe_target_feature("avx2")]
-impl<'a> Neg for &'a CachedPoint {
+impl Neg for &CachedPoint {
     type Output = CachedPoint;
     /// Lazily negate the point.
     ///
@@ -255,11 +255,11 @@ impl<'a> Neg for &'a CachedPoint {
 }
 
 #[unsafe_target_feature("avx2")]
-impl<'a, 'b> Add<&'b CachedPoint> for &'a ExtendedPoint {
+impl Add<&CachedPoint> for &ExtendedPoint {
     type Output = ExtendedPoint;
 
     /// Add an `ExtendedPoint` and a `CachedPoint`.
-    fn add(self, other: &'b CachedPoint) -> ExtendedPoint {
+    fn add(self, other: &CachedPoint) -> ExtendedPoint {
         // The coefficients of an `ExtendedPoint` are reduced after
         // every operation.  If the `CachedPoint` was negated, its
         // coefficients grow by one bit.  So on input, `self` is
@@ -293,22 +293,22 @@ impl<'a, 'b> Add<&'b CachedPoint> for &'a ExtendedPoint {
 }
 
 #[unsafe_target_feature("avx2")]
-impl<'a, 'b> Sub<&'b CachedPoint> for &'a ExtendedPoint {
+impl Sub<&CachedPoint> for &ExtendedPoint {
     type Output = ExtendedPoint;
 
     /// Implement subtraction by negating the point and adding.
     ///
     /// Empirically, this seems about the same cost as a custom
     /// subtraction impl (maybe because the benefit is cancelled by
     /// increased code size?)
-    fn sub(self, other: &'b CachedPoint) -> ExtendedPoint {
+    fn sub(self, other: &CachedPoint) -> ExtendedPoint {
         self + &(-other)
     }
 }
 
 #[unsafe_target_feature("avx2")]
-impl<'a> From<&'a edwards::EdwardsPoint> for LookupTable<CachedPoint> {
-    fn from(point: &'a edwards::EdwardsPoint) -> Self {
+impl From<&edwards::EdwardsPoint> for LookupTable<CachedPoint> {
+    fn from(point: &edwards::EdwardsPoint) -> Self {
         let P = ExtendedPoint::from(*point);
         let mut points = [CachedPoint::from(P); 8];
         for i in 0..7 {
@@ -319,8 +319,8 @@ impl<'a> From<&'a edwards::EdwardsPoint> for LookupTable<CachedPoint> {
 }
 
 #[unsafe_target_feature("avx2")]
-impl<'a> From<&'a edwards::EdwardsPoint> for NafLookupTable5<CachedPoint> {
-    fn from(point: &'a edwards::EdwardsPoint) -> Self {
+impl From<&edwards::EdwardsPoint> for NafLookupTable5<CachedPoint> {
+    fn from(point: &edwards::EdwardsPoint) -> Self {
         let A = ExtendedPoint::from(*point);
         let mut Ai = [CachedPoint::from(A); 8];
         let A2 = A.double();
@@ -334,8 +334,8 @@ impl<'a> From<&'a edwards::EdwardsPoint> for NafLookupTable5<CachedPoint> {
 
 #[cfg(any(feature = "precomputed-tables", feature = "alloc"))]
 #[unsafe_target_feature("avx2")]
-impl<'a> From<&'a edwards::EdwardsPoint> for NafLookupTable8<CachedPoint> {
-    fn from(point: &'a edwards::EdwardsPoint) -> Self {
+impl From<&edwards::EdwardsPoint> for NafLookupTable8<CachedPoint> {
+    fn from(point: &edwards::EdwardsPoint) -> Self {
         let A = ExtendedPoint::from(*point);
         let mut Ai = [CachedPoint::from(A); 64];
         let A2 = A.double();

curve25519-dalek/src/backend/vector/avx2/field.rs

@@ -760,7 +760,7 @@ impl Mul<(u32, u32, u32, u32)> for FieldElement2625x4 {
 }
 
 #[unsafe_target_feature("avx2")]
-impl<'a, 'b> Mul<&'b FieldElement2625x4> for &'a FieldElement2625x4 {
+impl Mul<&FieldElement2625x4> for &FieldElement2625x4 {
     type Output = FieldElement2625x4;
     /// Multiply `self` by `rhs`.
     ///
@@ -776,7 +776,7 @@ impl<'a, 'b> Mul<&'b FieldElement2625x4> for &'a FieldElement2625x4 {
     ///
     #[rustfmt::skip] // keep alignment of z* calculations
     #[inline]
-    fn mul(self, rhs: &'b FieldElement2625x4) -> FieldElement2625x4 {
+    fn mul(self, rhs: &FieldElement2625x4) -> FieldElement2625x4 {
         #[inline(always)]
         fn m(x: u32x8, y: u32x8) -> u64x4 {
             x.mul32(y)

curve25519-dalek/src/backend/vector/scalar_mul/pippenger.rs

@@ -123,8 +123,7 @@ pub mod spec {
             });
 
             // Take the high column as an initial value to avoid wasting time doubling the identity element in `fold()`.
-            // `unwrap()` always succeeds because we know we have more than zero digits.
-            let hi_column = columns.next().unwrap();
+            let hi_column = columns.next().expect("should have more than zero digits");
 
             Some(
                 columns

curve25519-dalek/src/edwards.rs

@@ -170,7 +170,7 @@ impl ConstantTimeEq for CompressedEdwardsY {
 }
 
 impl Debug for CompressedEdwardsY {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "CompressedEdwardsY: {:?}", self.as_bytes())
     }
 }
@@ -301,7 +301,7 @@ impl<'de> Deserialize<'de> for EdwardsPoint {
         impl<'de> Visitor<'de> for EdwardsPointVisitor {
             type Value = EdwardsPoint;
 
-            fn expecting(&self, formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+            fn expecting(&self, formatter: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 formatter.write_str("a valid point in Edwards y + sign format")
             }
 
@@ -337,7 +337,7 @@ impl<'de> Deserialize<'de> for CompressedEdwardsY {
         impl<'de> Visitor<'de> for CompressedEdwardsYVisitor {
             type Value = CompressedEdwardsY;
 
-            fn expecting(&self, formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+            fn expecting(&self, formatter: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 formatter.write_str("32 bytes of data")
             }
 
@@ -1052,7 +1052,7 @@ macro_rules! impl_basepoint_table {
         }
 
         impl Debug for $name {
-            fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 write!(f, "{:?}([\n", stringify!($name))?;
                 for i in 0..32 {
                     write!(f, "\t{:?},\n", &self.0[i])?;
@@ -1263,7 +1263,7 @@ impl EdwardsPoint {
 // ------------------------------------------------------------------------
 
 impl Debug for EdwardsPoint {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(
             f,
             "EdwardsPoint{{\n\tX: {:?},\n\tY: {:?},\n\tZ: {:?},\n\tT: {:?}\n}}",

curve25519-dalek/src/field.rs

@@ -23,6 +23,8 @@
 //! Field operations defined in terms of other field operations, such as
 //! field inversion or square roots, are defined here.
 
+#![allow(unused_qualifications)]
+
 use core::cmp::{Eq, PartialEq};
 
 use cfg_if::cfg_if;

curve25519-dalek/src/lib.rs

@@ -17,15 +17,24 @@
 )]
 #![cfg_attr(docsrs, feature(doc_auto_cfg, doc_cfg, doc_cfg_hide))]
 #![cfg_attr(docsrs, doc(cfg_hide(docsrs)))]
-#![cfg_attr(allow_unused_unsafe, allow(unused_unsafe))]
 //------------------------------------------------------------------------
 // Documentation:
 //------------------------------------------------------------------------
-#![deny(missing_docs)]
 #![doc(
     html_logo_url = "https://cdn.jsdelivr.net/gh/dalek-cryptography/curve25519-dalek/docs/assets/dalek-logo-clear.png"
 )]
 #![doc = include_str!("../README.md")]
+//------------------------------------------------------------------------
+// Linting:
+//------------------------------------------------------------------------
+#![cfg_attr(allow_unused_unsafe, allow(unused_unsafe))]
+#![warn(
+    clippy::unwrap_used,
+    missing_docs,
+    rust_2018_idioms,
+    unused_lifetimes,
+    unused_qualifications
+)]
 
 //------------------------------------------------------------------------
 // External dependencies:
@@ -44,9 +53,6 @@ extern crate std;
 #[cfg(feature = "digest")]
 pub use digest;
 
-#[cfg(feature = "group")]
-extern crate group;
-
 // Internal macros. Must come first!
 #[macro_use]
 pub(crate) mod macros;

curve25519-dalek/src/ristretto.rs

@@ -407,7 +407,7 @@ impl<'de> Deserialize<'de> for RistrettoPoint {
         impl<'de> Visitor<'de> for RistrettoPointVisitor {
             type Value = RistrettoPoint;
 
-            fn expecting(&self, formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+            fn expecting(&self, formatter: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 formatter.write_str("a valid point in Ristretto format")
             }
 
@@ -443,7 +443,7 @@ impl<'de> Deserialize<'de> for CompressedRistretto {
         impl<'de> Visitor<'de> for CompressedRistrettoVisitor {
             type Value = CompressedRistretto;
 
-            fn expecting(&self, formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+            fn expecting(&self, formatter: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 formatter.write_str("32 bytes of data")
             }
 
@@ -1155,13 +1155,13 @@ impl ConditionallySelectable for RistrettoPoint {
 // ------------------------------------------------------------------------
 
 impl Debug for CompressedRistretto {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "CompressedRistretto: {:?}", self.as_bytes())
     }
 }
 
 impl Debug for RistrettoPoint {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         let coset = self.coset4();
         write!(
             f,

curve25519-dalek/src/scalar.rs

@@ -285,7 +285,7 @@ impl Scalar {
 }
 
 impl Debug for Scalar {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "Scalar{{\n\tbytes: {:?},\n}}", &self.bytes)
     }
 }
@@ -430,7 +430,7 @@ impl<'de> Deserialize<'de> for Scalar {
         impl<'de> Visitor<'de> for ScalarVisitor {
             type Value = Scalar;
 
-            fn expecting(&self, formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+            fn expecting(&self, formatter: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 formatter.write_str(
                     "a sequence of 32 bytes whose little-endian interpretation is less than the \
                     basepoint order ℓ",

curve25519-dalek/src/traits.rs

@@ -259,7 +259,7 @@ pub trait VartimeMultiscalarMul {
             scalars,
             points.into_iter().map(|P| Some(P.borrow().clone())),
         )
-        .unwrap()
+        .expect("should return some point")
     }
 }
 
@@ -365,7 +365,7 @@ pub trait VartimePrecomputedMultiscalarMul: Sized {
             dynamic_scalars,
             dynamic_points.into_iter().map(|P| Some(P.borrow().clone())),
         )
-        .unwrap()
+        .expect("should return some point")
     }
 
     /// Given `static_scalars`, an iterator of public scalars

curve25519-dalek/src/window.rs

@@ -83,7 +83,7 @@ macro_rules! impl_lookup_table {
         }
 
         impl<T: Debug> Debug for $name<T> {
-            fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 write!(f, "{:?}(", stringify!($name))?;
 
                 for x in self.0.iter() {
@@ -193,7 +193,7 @@ impl<T: Copy> NafLookupTable5<T> {
 }
 
 impl<T: Debug> Debug for NafLookupTable5<T> {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         write!(f, "NafLookupTable5({:?})", self.0)
     }
 }
@@ -240,7 +240,7 @@ impl<T: Copy> NafLookupTable8<T> {
 
 #[cfg(any(feature = "precomputed-tables", feature = "alloc"))]
 impl<T: Debug> Debug for NafLookupTable8<T> {
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+    fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
         writeln!(f, "NafLookupTable8([")?;
         for i in 0..64 {
             writeln!(f, "\t{:?},", &self.0[i])?;