Clippy complains about generated code

[robamu]

This is a bit of a luxury problem but maybe something that could be addressed so I don't need to patch a SVD file which is ok in my opinion.

When faced with a register definitions like this:

        <register>
          <name>WDOGLOAD</name>
          <description>Counter Start Value</description>
          <addressOffset>0x0000</addressOffset>
          <access>read-write</access>
          <resetValue>0xFFFFFFFF</resetValue>
          <fields>
            <field>
              <name>CNT</name>
              <description>Count to load</description>
              <bitRange>[31:0]</bitRange>
            </field>
          </fields>	
        </register>		

svd2rust will generate code which clippy does not like:

error: this operation will always return zero. This is likely not the intended outcome
 --> va416xx/src/watch_dog/wdogload.rs:60:23
  |
60 |         self.w.bits = (self.w.bits & !0xffff_ffff) | (value as u32 & 0xffff_ffff);
  |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#erasing_op

warning: the operation is ineffective. Consider reducing it to `value as u32`
 --> va416xx/src/watch_dog/wdogload.rs:60:54
  |
60 |         self.w.bits = (self.w.bits & !0xffff_ffff) | (value as u32 & 0xffff_ffff);
  |                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op

warning: the operation is ineffective. Consider reducing it to `self.bits`
 --> va416xx/src/watch_dog/wdogload.rs:68:20
  |
68 |         CNT_R::new((self.bits & 0xffff_ffff) as u32)
  |                    ^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op

warning: the operation is ineffective. Consider reducing it to `self.bits`
 --> va416xx/src/watch_dog/wdogvalue.rs:35:20
  |
35 |         CNT_R::new((self.bits & 0xffff_ffff) as u32)
  |                    ^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_op

This probably requires svd2rust to check whether

1. Only one fields exists
2. That field has a width of 32 bits.

In that case, the code can be simplified. For example, this code:

impl<'a> CNT_W<'a> {
    #[doc = r"Writes raw bits to the field"]
    #[inline(always)]
    pub unsafe fn bits(self, value: u32) -> &'a mut W {
        self.w.bits = (self.w.bits & !0xffff_ffff) | (value as u32 & 0xffff_ffff);
        self.w
    }
}

would become

impl<'a> CNT_W<'a> {
    #[doc = r"Writes raw bits to the field"]
    #[inline(always)]
    pub unsafe fn bits(self, value: u32) -> &'a mut W {
        self.w.bits = value;
        self.w
    }
}

[burrbull]

@robamu Check #558

[robamu]

Thanks, this fixes the issue and clippy is happy now :)