Alessandro Arzilli authored Jul 08, 2019 and Derek Parker committed Jul 08, 2019

Backports debug/dwarf commit: 535741a69a1300d1fe2800778b99c8a1b75d7fdd
CL: https://go-review.googlesource.com/18459

The x/debug/dwarf that we used for dwarf/godwarf/type.go was forked
from debug/dwarf long before this commit.

Original description:

    Currently readType simultaneously constructs a type graph and resolves
    the sizes of the types. However, these two operations are
    fundamentally at odds: the order we parse a cyclic structure in may be
    different than the order we need to resolve type sizes in. As a
    result, it's possible that when readType attempts to resolve the size
    of a typedef, it may dereference a nil Type field of another typedef
    retrieved from the type cache that's only partially constructed.

    To fix this, we delay resolving typedef sizes until the end of the
    readType recursion, when the full type graph is constructed.

Fixes #1601