checker: permit int -> f32, int64 -> f64 and similar promotions again

doc/docs.md

@@ -292,15 +292,14 @@ Please note that unlike C and Go, `int` is always a 32 bit integer.
 There is an exceptions to the rule that all operators
 in V must have values of the same type on both sides. A small primitive type
 on one side can be automatically promoted if it fits
-completely into the data range of the type on the other side, i.e. when
+completely into the data range of the type on the other side.
-the promotion does not result in any data loss.
 These are the allowed possibilities:
 
 ```
    i8 → i16 → int → i64
-            ↘     ↘
+                  ↘     ↘
-              f32 → f64
+                    f32 → f64
-            ↗     ↗
+                  ↗     ↗
  byte → u16 → u32 → u64 ⬎
       ↘     ↘     ↘      ptr
    i8 → i16 → int → i64 ⬏

vlib/v/checker/check_types.v

@@ -183,17 +183,13 @@ fn (c &Checker) promote_num(left_type, right_type table.Type) table.Type {
 		}
 	} else if type_hi.is_float() {
 		if idx_hi == table.f32_type_idx {
-			if idx_lo in [table.int_type_idx, table.i64_type_idx, table.u32_type_idx, table.u64_type_idx] {
-				return table.void_type
-			} else {
-				return type_hi
-			}
-		} else { // f64, any_flt
 			if idx_lo in [table.i64_type_idx, table.u64_type_idx] {
 				return table.void_type
 			} else {
 				return type_hi
 			}
+		} else { // f64, any_flt
+			return type_hi
 		}
 	} else if idx_lo >= table.byte_type_idx { // both operands are unsigned
 		return type_hi

vlib/v/tests/type_promotion_test.v

@@ -67,3 +67,16 @@ fn test_struct_init_ref_return() {
 	assert fabs(fabs(x.get()) - 3.890949634755863) < 1.e-6
 }
 
+fn test_f32_int() {
+	x := f32(15.25)
+	y := -3
+	assert x + y == 12.25
+	assert y + x == 12.25
+	a := u32(34)
+	assert a + x == 49.25
+	b := i64(-17)
+	c := 16.75
+	assert c + b == -0.25
+	d := u64(300)
+	assert d + c == 316.75
+}