Noted by @maik-kluwe in #4197 (comment).

Given a workspace:

{
	"folders": [
		{
			"path": "proj1"
		},
		{
			"path": "proj2"
		}
	],
}

And a workspace folder has a launch config:

{
	"version": "0.2.0",
	"configurations": [
		{
			"name": "proj1",
			"request": "launch",
			"type": "dart",
			"program": "bin/main.dart"
		}
	]
}

Trying to run results in this:

This is likely caused by #4197 but I do not believe is expected. In this case, the program should be resolved relative to the workspace folder that it lives inside.