Missing type annotation. Our language requires var x: i64 = 5;. executeStatement expects : right after the variable name -- that's how it knows this is a declaration, and it's where we'll read the type when we start emitting WAT. Without the :, the = 5 won't parse as a declaration.

Zig itself allows var x = 5; (type inference). We don't, and we won't. Every declaration stating its type is a minor pain to type and a big win for readability -- when you're scanning a function you can tell what every variable is without chasing the right-hand side.