[issue39537] Change line number table format

[Mark Shannon]

Mark Shannon <mark at hotpy.org> added the comment:

Serhiy,

Although the code generator is syntax directed, not all code has an explicit piece of syntax attached.

For example in the following code:
```
def foo():
    if x:
        print("yes")
    else:
        print("no")
```
the compiler emits code to return from the function (LOAD_CONST None; RETURN_VALUE), but there is no explicit return, and no meaningful line number for the return.

Also consider, the artificial try-except block generated for async for loops and the cleanup code for named exception variables.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39537>
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