Incorrect compiler error when returning an array after a code block

[pventuzelo]

Aim

We (@FuzzingLabs) found that the compiler raises incorrectly an error when returning an array after a code block.

Expected Behavior

The error comes from the line 152 of this file: https://github.com/noir-lang/noir/blob/master/compiler/noirc_frontend/src/hir/type_check/errors.rs

No error should be returned.

Bug

The error occurs when attempting to return an array immediately after a code block. It persists under certain conditions, such as when using different array types, returning an array derived from a variable, or creating a code block with constructs other than an if statement, even if there are instructions inside them.

However, there are workarounds to avoid this error. For instance, you can bypass the error by directly assigning the array to a variable before the code block, inserting an instruction between the code block and the return statement, or using an array with a specified size. Additionally, loop blocks do not trigger the error.

The error occurs with the latest compiler version on the master branch. The error message is as follows:

error: Expected type Array, found type ()

To Reproduce

1. Create a Noir project with the following command: nargo new test_issue
2. Paste the code below into the file [main.nr](http://main.nr/)
3. Compile the project using the following command: nargo compile

// The compiler raises an error when attempting to return an array after a code block.
fn case1() -> [Field] {
    if true {
    }
    [1]
}

// The error still occurs in the following scenarios:
// - When using another array type.
// - When returning an array of a variable.
// - When creating a code block with something other than an if statement even with instructions in them.
fn case2() -> [u8] {
    let mut var: u8 = 1;
    {
        var += 1;
    }
    [var]
}

// The error is not raised when the array is directly assigned to a variable.
fn case3() -> [Field] {
    let mut var: [Field] = [1];
    {}
    var
}

// The error is not raised if there is an instruction between the code block and the return.
fn case4() -> [Field] {
    let mut var: Field = 1;
    {}
    var += 1;
    [var]
}

// The error is not raised when using an array with a specified size.
fn case5() -> [Field; 1] {
    let mut var: Field = 1;
    {}
    [var; 1]
}

// The error is not raised with for loop blocks.
fn case6() -> [Field] {
    let mut var: Field = 1;
    for i in 0..1 {

    }
    [var]
}

fn main() {}

Project Impact

None

Impact Context

No response

Workaround

None

Workaround Description

No response

Additional Context

No response

Installation Method

None

Nargo Version

No response

NoirJS Version

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response