ctx[_] is not a function error with @const's named func referenced inside lambda expressions

[aspiringLich]

Describe the bug

An error that occurs with (as far as I can tell) lambda functions inside curly braces in the markup, that reference an {@const} named func. This causes a conflict between generating a function for the lambda (internally called func), and the variable func. It then (I assume) incorrectly thinks the lambda function is the same as the @const. It does not apply to regular variables named func, only {@const} variables.

Reproduction

I'll save you the painful process of cutting everything down: here's the simplest scenario I could find that showcases the weird error.

{#if true}
    {@const func = [12, 13, 14]}

    {(() => JSON.stringify(func))()} <!-- Error: ctx[0] is not a function -->
{/if}

It's specifically {@const func = _} that causes the error, every other identifier i tried worked AOK. Which was very fun to figure out. I think this is because when I look at the generated javascript:

// (1:0) {#if true}
function create_if_block(ctx) {
    let t_value = func() + "";
    let t;

    function func() {
        return /*func*/ ctx[0](/*func*/ ctx[0]);
    }
    // ...
}

ctx[0] shows up twice, once for the "const variable", and once for the function being referenced. So yes, ctx[0] is not a function its a variable. That makes sense I guess.

So to recap:

• You need an @const variable named func
• You need to reference it inside a lambda in the markup
• The generated code will confuse the lambda and the @const variable, replacing the lambda with a call to the @const.

Things finally make sense you do not know how weird this error was when I first discovered it.

This error probably shouldn't be terribly high priority but it also should be pretty easy to fix I think.

Logs

No response

System Info

As far as I can tell it's completely platform independent, tested it on my machine and the online REPL, buuuut...


  System:
    OS: Linux 6.3 Fedora Linux 37 (KDE Plasma)
    CPU: (16) x64 12th Gen Intel(R) Core(TM) i7-1260P
    Memory: 4.90 GB / 15.32 GB
    Container: Yes
    Shell: 3.6.1 - /usr/bin/fish
  Binaries:
    Node: 18.16.0 - /usr/bin/node
    npm: 9.5.1 - /usr/local/bin/npm
  Browsers:
    Chromium: 114.0.5735.106
    Firefox: 114.0
  npmPackages:
    svelte: ^3.55.1 => 3.59.1 

### Severity

annoyance