Remove explicit std::marker from Sized bound

Sized is always part of the prelude, and binding on std causes
compilation issues for no-std crates.

bellman/src/groth16/tests/dummy_engine.rs

@@ -166,7 +166,7 @@ impl Shr<u32> for Fr {
 }
 
 impl Field for Fr {
-    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+    fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self {
         Fr(Wrapping(rng.next_u32()) % MODULUS_R)
     }
 
@@ -358,7 +358,7 @@ impl CurveProjective for Fr {
     type Scalar = Fr;
     type Engine = DummyEngine;
 
-    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+    fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self {
         <Fr as Field>::random(rng)
     }
 

ff/ff_derive/src/lib.rs

@@ -1188,7 +1188,7 @@ fn prime_field_impl(
 
         impl ::ff::Field for #name {
             /// Computes a uniformly random element using rejection sampling.
-            fn random<R: ::rand_core::RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+            fn random<R: ::rand_core::RngCore + ?Sized>(rng: &mut R) -> Self {
                 loop {
                     let mut tmp = {
                         let mut repr = [0u64; #limbs];

ff/src/lib.rs

@@ -50,7 +50,7 @@ pub trait Field:
     + for<'a> SubAssign<&'a Self>
 {
     /// Returns an element chosen uniformly at random using a user-provided RNG.
-    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self;
+    fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self;
 
     /// Returns the zero element of the field, the additive identity.
     fn zero() -> Self;

group/src/lib.rs

@@ -52,7 +52,7 @@ pub trait CurveProjective:
     type Affine: CurveAffine<Projective = Self, Scalar = Self::Scalar>;
 
     /// Returns an element chosen uniformly at random using a user-provided RNG.
-    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self;
+    fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self;
 
     /// Returns the additive identity.
     fn zero() -> Self;

pairing/src/bls12_381/ec.rs

@@ -515,7 +515,7 @@ macro_rules! curve_impl {
             type Base = $basefield;
             type Affine = $affine;
 
-            fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+            fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self {
                 loop {
                     let x = $basefield::random(rng);
                     let greatest = rng.next_u32() % 2 != 0;

pairing/src/bls12_381/fq12.rs

@@ -177,7 +177,7 @@ impl MulAssign for Fq12 {
 }
 
 impl Field for Fq12 {
-    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+    fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self {
         Fq12 {
             c0: Fq6::random(rng),
             c1: Fq6::random(rng),

pairing/src/bls12_381/fq2.rs

@@ -185,7 +185,7 @@ impl MulAssign for Fq2 {
 }
 
 impl Field for Fq2 {
-    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+    fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self {
         Fq2 {
             c0: Fq::random(rng),
             c1: Fq::random(rng),

pairing/src/bls12_381/fq6.rs

@@ -278,7 +278,7 @@ impl MulAssign for Fq6 {
 }
 
 impl Field for Fq6 {
-    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+    fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self {
         Fq6 {
             c0: Fq2::random(rng),
             c1: Fq2::random(rng),

zcash_primitives/src/jubjub/fs.rs

@@ -362,7 +362,7 @@ impl PrimeField for Fs {
 }
 
 impl Field for Fs {
-    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
+    fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self {
         loop {
             let mut tmp = {
                 let mut repr = [0u64; 4];