Certain code with if statement leads to an ICE

[cburgdorf]

What is wrong?

The following leads to an ICE

contract Bar {

    something: bool

    pub fn move_field(self) {
        if true {
            if self.something { 
                return 
            }
        }
        if true {
            if self.something { 
                return 
            }
        }
    }
}

ICE:

Error: DeclarationError: Variable not found or variable not lvalue.
  --> input.yul:33:17:
   |
33 |                 $$tmp_5 := and($$sptr_load(add(0, 0), 8), 0xff)
   |                 ^^^^^^^


Error: DeclarationError: Identifier "$$tmp_5" not found.
  --> input.yul:34:24:
   |
34 |                 switch $$tmp_5
   |                        ^^^^^^^

Looking at the relevant YUL we can see that the second $$tmp_5 is used but not declared. Or maybe the initial declaration of $$tmp_5 should have been made one block higher 🤔 I haven't really analyzed it yet.

switch 1
case 1 {
    let $$tmp_3
    $$tmp_3: = and($$sptr_load(add(0, 0), 8), 0xff)
    switch $$tmp_3
    case 1 {
        leave
    }
    case 0 {
        switch 1
        case 1 {
            let $$tmp_5
            $$tmp_5: = and($$sptr_load(add(0, 0), 8), 0xff)
            switch $$tmp_5
            case 1 {
                leave
            }
            case 0 {
                leave
            }
        }
        case 0 {
            leave
        }
    }
}
case 0 {
    switch 1
    case 1 {
        $$tmp_5: = and($$sptr_load(add(0, 0), 8), 0xff)
        switch $$tmp_5
        case 1 {
            leave
        }
        case 0 {
            leave
        }
    }
    case 0 {
        leave
    }
}
}

It's as minimal as I could get it:

The following alternations would make the ICE go away:

• removing the return
• unnesting
• removing the second (duplicated) if block
• using a local condition instead of self.something

How can it be fixed

🔪