cmd/compile: distinguish bound calls/field access in getInstInfo
Given we have support for field access to type params with a single
structural type, we need to distinguish between methods calls and field
access when we have an OXDOT node on an expression which is a typeparam
(or correspondingly a shape). We were missing checks in getInstInfo,
which figures out the dictionary format, which then caused problems when
we generate the dictionaries. We don't need/want dictionary entries for
field access, only for bound method calls. Added a new function
isBoundMethod() to distinguish OXDOT nodes which are bound calls vs.
field accesses on a shape.
Removed isShapeDeref() - we can't have field access or method call on a
pointer to variable of type param type.
Fixes #50690
Change-Id: Id692f65e6f427f28cd2cfe474dd30e53c71877a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/379674
Trust: Dan Scales <danscales@google.com> Reviewed-by: Keith Randall <khr@golang.org>