Why adding to a nested if expression causes a compilation error?

[programandala-net]

i have found out a curious issue about nested if expressions; i have isolated it in this example code:

import rand

fn chance() bool {
	return rand.i8() >= 0
}

fn main() {
	// these nested `if` expressions are compiled fine
	// (note a literal is added to the *outer* `if` expression):

	_ := if chance() {  0  } else { if chance() {  2  } else {  3  } } + 5
	_ := if chance() { 'a' } else { if chance() { 'c' } else { 'd' } } + 'f'

	// but when something is added to the *inner* `if` expression, the compilation
	// fails:

	// XXX compilation error: mismatched types `void` and `int literal`:
	// _ := if chance() {  0  } else { if chance() {  2  } else {  3  } +  4 } + 5

	// XXX compilation error: mismatched types `void` and `string`:
	// _ := if chance() { 'a' } else { if chance() { 'c' } else { 'd' } + 'e'} + 'f'

	// and when the inner `if` expression is added to something, the
	// compilation works:

	_ := if chance() {  0  } else {  1  + if chance() {  2  } else {  3  } +  4 } + 5
	_ := if chance() { 'a' } else { 'b' + if chance() { 'c' } else { 'd' } + 'e'} + 'f'

}

i have searched the documentation, the github issues and the github discussions but found nothing related.

it seems a bug, but perhaps i am neglecting something, so i prefer to ask here first, before opening an issue.

[programandala-net]

issue: #26865