Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

There should be existing compiler warnings for this (which we obviously have disabled because they are considered false positives or useless or whatever reason was given).

At least clang-tidy and MSVC don't detect this. I have run the new check on a large-ish code base and found more than 30 instances already, no FPs.

double f(double a, double b, float c) {
    return a + (float)b + c;
}

<source>:2:27: warning: implicit conversion increases floating-point precision: 'float' to 'double' [-Wdouble-promotion]
    2 |     return a + (float)b + c;
      |                         ~ ^
<source>:2:16: warning: implicit conversion increases floating-point precision: 'float' to 'double' [-Wdouble-promotion]
    2 |     return a + (float)b + c;
      |              ~ ^~~~~~~~

https://godbolt.org/z/edfMs737P

Also see discussion in #4820 as to way the warning is not enabled in our code base yet.

I see, didn't know about that compiler warning. However, -Wdouble-promotion is warning about the up-conversion (twice in your example), not about the loss of precision due to the cast. So it is more noisy than the proposed check.

See also llvm/llvm-project#93288.