Feature

Following the discussion in microsoft/vscode#142810, I propose MyPy to output a range over which a typing error occurs, instead of just the position of it. The current message with --show-column-numbers and --no-pretty looks like this:

test.py:4:5: error: Argument 1 to "foo" has incompatible type "str"; expected "int"

It'd be great if a range would be included for the column numbers, if possible:

test.py:4:5-15: error: Argument 1 to "foo" has incompatible type "str"; expected "int"

Output with --pretty could then use multiple ^ characters to visualize the range. Omitting --show-column-numbers wouldn't display column numbers at all, thus the output would remain unchanged.

Pitch

This change would allow the VSCode Python extension to output diagnostic objects with proper ranges, since the current implementation only underlines one character and makes it hard to work with, and other proposed solutions appear to be non-trivial at the very least.