Issue with Breakpoints with For Loops & Branches (Generated Debug Information)

[itsdanott]

Context

This is quite a specific one so there's also a video attached that should help understanding it.

Screen.Recording.2025-01-30.115109.mp4

When hitting an if branch with a false conditional expression while stepping through a for loop the breakpoint is shown inside last line of the if-scope.
This makes it hard to understand wether the code is actually executed or not.
Especially in single-line scopes it gets difficult as you won't notice a visual difference.

As suggested by laytan this is most likely related to Odin's generated debug information.

Details

The problem occurs on Windows with MSVC - I have also tested it on a Mac with LLDB where it works as expected.
It seems to only happen inside a foor loop and only for a conditional expression - for a boolean literal it works fine.

Operating System & Odin Version:
Odin: dev-2025-01:2aae4cfd4
OS: Windows 11 Professional (version: 24H2), build 26100.2894
CPU: AMD Ryzen 9 5950X 16-Core Processor
RAM: 65448 MiB
Backend: LLVM 18.1.8

Steps to Reproduce

1. Add a breakpoint to line 5
2. Start a debug session with MSVC (cppvsdbg)
3. Step through the for loop and notice how the breakpoint enters the last line of the if-branch - even though the print is obviously not actually executed.
4. Change line 6 to a bool literal: if false { and notice how the problem does not occur any more

package main
import "core:fmt"

main :: proc() {
    for i in 0..<32 {
        if i > 64 { // <- conditional expression seems to trigger the issue. Compare to false bool literal.
            fmt.printf("This won't be printed!")
            fmt.printf("Neither will this.")
            // ^ Somehow the breakpoint exists the loop here
        }
    }
}