[RubenPari]

In v1, unmarshal methods are only called on a value of an unnamed type
if the value is reached through a pointer (see indirect in decode.go),
with the exception of UnmarshalText for map keys.
An unnamed type only has methods through embedded fields, so v1 decodes
the fields of, e.g., an anonymous struct embedding *T instead of calling
the promoted (*T).UnmarshalJSON method, and allocates the embedded pointer.

The v2 implementation used by encoding/json called the promoted method
regardless, which panics with a nil pointer dereference when the
embedded field is a nil pointer, and otherwise produces different
results than v1 for anonymous struct fields, slice/array elements,
and map values.

Under CallMethodsWithLegacySemantics, skip unmarshal methods on values
of unnamed types, except when the value is obtained by dereferencing
a pointer (the top-level argument or a pointer element) or, for
UnmarshalText, when used as a map key. Pure v2 semantics are unchanged.

Fixes #81244

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