When we calculate end positions for errors that originate from go/packages. We do some kind of syntax analysis, but some issues arise when adding new characters to the list in internal/lsp/cache/errors.go#L208

if width := bytes.IndexAny(data[offset:], " \n,():;[]"); width > 0 {
	return ...
}

Take the sample program below:

__ main.go __
package main

import "golang.org/whatever"

func main() {
    if y/2 == 10 { return }
}

We will have two errors: (1) "undeclared name: y" and (2) "could not import golang.org/whatever (no package for import golang.org/whatever)".

In the current state, the diagnostic for error 1 will be on "y+2" and the diagnostic for error 2 will be on "golang.org/whatever".

Now, the diagnostic for error 1 should only underline "y" since that is the undeclared name, to fix this I could add "/" to the character list in internal/lsp/cache/errors.go#L208 but then the diagnostic on error 2 would now underline "golang.org" rather than "golang.org/whatever".

I think gopls needs a better way to compute the end positions for type errors.