Erroneous coverage indication in html report when type checking stops due to impossible assert

[axch]

The html report for checking coverage of the situation from Issue #2776 misrepresents the unchecked code lines. Specifically, the example is

class A(object): pass

class C(object): pass

def bar(x):
    # type: (A) -> None
    reveal_type(x)
    assert isinstance(x, C)
    reveal_type(x)

The report generated by --html-report indicates that the whole file is covered, even though the second reveal_type produces no output (which problem itself is #2776). Inspecting the source indicates that the second reveal_type is classified as "line-empty", which visually looks like "line-precise", and in this circumstance is misleading.

[gvanrossum]

Due to the bug in #2776 it is treating that line as dead code. Maybe we should have a different color for dead code (as opposed to empty lines/comments/docstrings and the line).

[axch]

+1 for marking dead code differently.