No backwards compatibility for string concatinations

[alfie-nsugh]

I was wondering if it was intended that this would give an error:
1> x = "h"
2. x =x+ "ello"
3. print(x)
[User] Failed to produce standalone archive: failed to lower module to LLVM IR for archive compilation
[User] Expression [1] wrapper:17:9: note: see current operation: %60 = "pop.string.concat"(%59, %23) : (!kgen.string, !kgen.string) -> !kgen.string

[User] error: Expression [1]:2:5: failed to legalize operation 'pop.string.concat' that was explicitly marked illegal
x =x+ "ello"

When doing

var z: String = "H"
z += "ello"

it does work. However, in python we don't have to declare something to be mutable to be able to change it.
Is this departure from python intended or are you planning to change this in the future?

[rarebreed]

It shouldn't be an issue with mutability. Firstly, mojo got rid of let, so essentially everything on the stack is mutable (sadly) and there are only immutable references. Also, not declaring with var implicitly makes it a var, and inside a def function, gives it python function level scoping. But I think this is an issue with the REPL, not with mutability.

The code you have works fine in a script.

def main():
    z = "h"
    z = z + "ello"
    print(z)

[hogepodge]

Hi @alfie-nsugh this is a known issue with string literals in the REPL. We have an issue, and are working on fixing it.