diff --git a/src/librustc_data_structures/fingerprint.rs b/src/librustc_data_structures/fingerprint.rs
index c4c0db58012..7975c62b90f 100644
--- a/src/librustc_data_structures/fingerprint.rs
+++ b/src/librustc_data_structures/fingerprint.rs
@@ -39,8 +39,8 @@ impl Fingerprint {
     // you want.
     #[inline]
     pub fn combine_commutative(self, other: Fingerprint) -> Fingerprint {
-        let a = (self.1 as u128) << 64 | self.0 as u128;
-        let b = (other.1 as u128) << 64 | other.0 as u128;
+        let a = u128::from(self.1) << 64 | u128::from(self.0);
+        let b = u128::from(other.1) << 64 | u128::from(other.0);
 
         let c = a.wrapping_add(b);
 
diff --git a/src/librustc_data_structures/sip128.rs b/src/librustc_data_structures/sip128.rs
index 06f157f9729..7838a900890 100644
--- a/src/librustc_data_structures/sip128.rs
+++ b/src/librustc_data_structures/sip128.rs
@@ -70,15 +70,15 @@ unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
     let mut i = 0; // current byte index (from LSB) in the output u64
     let mut out = 0;
     if i + 3 < len {
-        out = load_int_le!(buf, start + i, u32) as u64;
+        out = u64::from(load_int_le!(buf, start + i, u32));
         i += 4;
     }
     if i + 1 < len {
-        out |= (load_int_le!(buf, start + i, u16) as u64) << (i * 8);
+        out |= u64::from(load_int_le!(buf, start + i, u16)) << (i * 8);
         i += 2
     }
     if i < len {
-        out |= (*buf.get_unchecked(start + i) as u64) << (i * 8);
+        out |= u64::from(*buf.get_unchecked(start + i)) << (i * 8);
         i += 1;
     }
     debug_assert_eq!(i, len);
diff --git a/src/librustc_data_structures/stable_hasher.rs b/src/librustc_data_structures/stable_hasher.rs
index 0c81c27a96e..47dfc1d1688 100644
--- a/src/librustc_data_structures/stable_hasher.rs
+++ b/src/librustc_data_structures/stable_hasher.rs
@@ -44,7 +44,7 @@ impl<W: StableHasherResult> StableHasher<W> {
 impl StableHasherResult for u128 {
     fn finish(hasher: StableHasher<Self>) -> Self {
         let (_0, _1) = hasher.finalize();
-        (_0 as u128) | ((_1 as u128) << 64)
+        u128::from(_0) | (u128::from(_1) << 64)
     }
 }
 
diff --git a/src/libserialize/json.rs b/src/libserialize/json.rs
index 826954ce216..a7e7c09f9ae 100644
--- a/src/libserialize/json.rs
+++ b/src/libserialize/json.rs
@@ -513,7 +513,7 @@ impl<'a> crate::Encoder for Encoder<'a> {
         emit_enquoted_if_mapkey!(self, fmt_number_or_null(v))
     }
     fn emit_f32(&mut self, v: f32) -> EncodeResult {
-        self.emit_f64(v as f64)
+        self.emit_f64(f64::from(v))
     }
 
     fn emit_char(&mut self, v: char) -> EncodeResult {
@@ -763,7 +763,7 @@ impl<'a> crate::Encoder for PrettyEncoder<'a> {
         emit_enquoted_if_mapkey!(self, fmt_number_or_null(v))
     }
     fn emit_f32(&mut self, v: f32) -> EncodeResult {
-        self.emit_f64(v as f64)
+        self.emit_f64(f64::from(v))
     }
 
     fn emit_char(&mut self, v: char) -> EncodeResult {
@@ -1698,12 +1698,12 @@ impl<T: Iterator<Item=char>> Parser<T> {
                             if n2 < 0xDC00 || n2 > 0xDFFF {
                                 return self.error(LoneLeadingSurrogateInHexEscape)
                             }
-                            let c = (((n1 - 0xD800) as u32) << 10 |
-                                     (n2 - 0xDC00) as u32) + 0x1_0000;
+                            let c = (u32::from(n1 - 0xD800) << 10 |
+                                     u32::from(n2 - 0xDC00)) + 0x1_0000;
                             res.push(char::from_u32(c).unwrap());
                         }
 
-                        n => match char::from_u32(n as u32) {
+                        n => match char::from_u32(u32::from(n)) {
                             Some(c) => res.push(c),
                             None => return self.error(InvalidUnicodeCodePoint),
                         },
@@ -2405,7 +2405,7 @@ impl ToJson for Json {
 }
 
 impl ToJson for f32 {
-    fn to_json(&self) -> Json { (*self as f64).to_json() }
+    fn to_json(&self) -> Json { f64::from(*self).to_json() }
 }
 
 impl ToJson for f64 {
diff --git a/src/libserialize/leb128.rs b/src/libserialize/leb128.rs
index 16ff59489e7..f9d80842d75 100644
--- a/src/libserialize/leb128.rs
+++ b/src/libserialize/leb128.rs
@@ -123,7 +123,7 @@ pub fn read_signed_leb128(data: &[u8], start_position: usize) -> (i128, usize) {
     loop {
         byte = data[position];
         position += 1;
-        result |= ((byte & 0x7F) as i128) << shift;
+        result |= i128::from(byte & 0x7F) << shift;
         shift += 7;
 
         if (byte & 0x80) == 0 {