Resolve legacy_numeric_constants clippy lints

    warning: usage of a legacy numeric method
       --> serde_derive/src/ser.rs:292:51
        |
    292 |     assert!(fields.len() as u64 <= u64::from(u32::max_value()));
        |                                                   ^^^^^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#legacy_numeric_constants
        = note: `#[warn(clippy::legacy_numeric_constants)]` on by default
    help: use the associated constant instead
        |
    292 |     assert!(fields.len() as u64 <= u64::from(u32::MAX));
        |                                                   ~~~

    warning: usage of a legacy numeric method
       --> serde_derive/src/ser.rs:400:53
        |
    400 |     assert!(variants.len() as u64 <= u64::from(u32::max_value()));
        |                                                     ^^^^^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#legacy_numeric_constants
    help: use the associated constant instead
        |
    400 |     assert!(variants.len() as u64 <= u64::from(u32::MAX));
        |                                                     ~~~

    warning: usage of a legacy numeric method
        --> test_suite/tests/test_de_error.rs:1462:29
         |
    1462 |             Token::U64(u64::max_value()),
         |                             ^^^^^^^^^^^
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#legacy_numeric_constants
         = note: `-W clippy::legacy-numeric-constants` implied by `-W clippy::all`
         = help: to override `-W clippy::all` add `#[allow(clippy::legacy_numeric_constants)]`
    help: use the associated constant instead
         |
    1462 |             Token::U64(u64::MAX),
         |                             ~~~

    warning: usage of a legacy numeric method
        --> test_suite/tests/test_de_error.rs:1479:29
         |
    1479 |             Token::U64(u64::max_value()),
         |                             ^^^^^^^^^^^
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#legacy_numeric_constants
    help: use the associated constant instead
         |
    1479 |             Token::U64(u64::MAX),
         |                             ~~~

    warning: usage of a legacy numeric method
        --> test_suite/tests/test_de_error.rs:1493:29
         |
    1493 |             Token::U64(u64::max_value()),
         |                             ^^^^^^^^^^^
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#legacy_numeric_constants
    help: use the associated constant instead
         |
    1493 |             Token::U64(u64::MAX),
         |                             ~~~

    warning: usage of a legacy numeric method
        --> test_suite/tests/test_de_error.rs:1510:29
         |
    1510 |             Token::U64(u64::max_value()),
         |                             ^^^^^^^^^^^
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#legacy_numeric_constants
    help: use the associated constant instead
         |
    1510 |             Token::U64(u64::MAX),
         |                             ~~~

serde_derive/src/ser.rs

@@ -289,7 +289,7 @@ fn serialize_tuple_struct(
 }
 
 fn serialize_struct(params: &Parameters, fields: &[Field], cattrs: &attr::Container) -> Fragment {
-    assert!(fields.len() as u64 <= u64::from(u32::max_value()));
+    assert!(fields.len() as u64 <= u64::from(u32::MAX));
 
     if cattrs.has_flatten() {
         serialize_struct_as_map(params, fields, cattrs)
@@ -397,7 +397,7 @@ fn serialize_struct_as_map(
 }
 
 fn serialize_enum(params: &Parameters, variants: &[Variant], cattrs: &attr::Container) -> Fragment {
-    assert!(variants.len() as u64 <= u64::from(u32::max_value()));
+    assert!(variants.len() as u64 <= u64::from(u32::MAX));
 
     let self_var = &params.self_var;
 

test_suite/tests/test_de_error.rs

@@ -1459,7 +1459,7 @@ fn test_duration_overflow_seq() {
     assert_de_tokens_error::<Duration>(
         &[
             Token::Seq { len: Some(2) },
-            Token::U64(u64::max_value()),
+            Token::U64(u64::MAX),
             Token::U32(1_000_000_000),
             Token::SeqEnd,
         ],
@@ -1476,7 +1476,7 @@ fn test_duration_overflow_struct() {
                 len: 2,
             },
             Token::Str("secs"),
-            Token::U64(u64::max_value()),
+            Token::U64(u64::MAX),
             Token::Str("nanos"),
             Token::U32(1_000_000_000),
             Token::StructEnd,
@@ -1490,7 +1490,7 @@ fn test_systemtime_overflow_seq() {
     assert_de_tokens_error::<SystemTime>(
         &[
             Token::Seq { len: Some(2) },
-            Token::U64(u64::max_value()),
+            Token::U64(u64::MAX),
             Token::U32(1_000_000_000),
             Token::SeqEnd,
         ],
@@ -1507,7 +1507,7 @@ fn test_systemtime_overflow_struct() {
                 len: 2,
             },
             Token::Str("secs_since_epoch"),
-            Token::U64(u64::max_value()),
+            Token::U64(u64::MAX),
             Token::Str("nanos_since_epoch"),
             Token::U32(1_000_000_000),
             Token::StructEnd,
@@ -1522,7 +1522,7 @@ fn test_systemtime_overflow() {
     assert_de_tokens_error::<SystemTime>(
         &[
             Token::Seq { len: Some(2) },
-            Token::U64(u64::max_value()),
+            Token::U64(u64::MAX),
             Token::U32(0),
             Token::SeqEnd,
         ],