Description

Problem*

Resolves #6990

Summary*

Go to the issue for the initial context. What I did is a little bit hack-y, but it seemed like the simplest way to prevent this panic without making significant changes to how we monomorphize.

Format strings are the only comptime type which we lower into a different type (in this case a string literal). I changed the Value::FormatString case in into_hir_expression to return a HirLiteral::FmtStr in the format that the type is expected to be. This required creating a new placeholder expression. In this case I used a string with a single whitespace character as this required minimal changes and does not change the functionality of fmt strings which are entirely used for logging.

I added some global fmt strings to the debug_logs test:
These prints:

global A: Field = 50;
global B: Field = 100;
global GLOBAL_FMT_STR: fmtstr<14, (Field, Field)> = f"i: {A}, j: {B}";
global GLOBAL_FMT_STR_BIG: fmtstr<22, (Field, Field, Field)> = f"i: {A}, j: {B}, k: {A}";

fn main(..) {
    println(GLOBAL_FMT_STR);
    println(GLOBAL_FMT_STR_BIG);
}

Give this output:

i: 50, j: 100
i: 50, j: 100, k: 50

Additional Context

We do not currently allow nested format strings. Having this extra whitespace may cause some difficulty if we ever activate the ability to have nested format strings.

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.