Detect duplicate const literals in match

[medvednikov]

Expected behavior:

a := 0
switch a {
case 0.0:
case 0:
}
./prog.go:12:6: duplicate case 0 in switch

[Delta456]

This now gives an error cannot match float literalwithint condition. I am not sure if 0.0 should implicitly cast to int.

[dumblob]

I am not sure if 0.0 should implicitly cast to int.

It should not (because it's an approximate zero and thus not an integer exact zero).

[serkonda7]

@dumblob if the value that is matched (here a) is an int, 0.0 should be cast to an int.

[dumblob]

@dumblob if the value that is matched (here a) is an int, 0.0 should be cast to an int.

Generally yes, but only for compatible types. In V it must not be possible to do:

mut x := 1.5
x = 0.0
assert x == 0

The correct way would be:

mut x := 1.5
x = 0.0
assert int( x ) == 0

[serkonda7]

Therefore we have rules for automatic type promotions. You can look them up in the docs

[dumblob]

Therefore we have rules for automatic type promotions. You can look them up in the docs

Type promotions are in flux for quite some time already (#7801 (comment) , #8601 , #7692 , #6251 ) and they converge to guarantee no information loss which in this case is not possible (it's possible to silently promote int to f64, but not any float to int).

[medvednikov]

Fixed.