panic: runtime error: invalid memory address or nil pointer dereference

[iamrajiv]

Root Cause

The canAssignVMType function in analyze.go does not handle the case where a union contains
a recursive/self-referencing record type. When NestedProperty references itself inside
the union's value type, the analyzer encounters a nil pointer because the type has not
been fully resolved yet during the schema tree walk.

Key Details

• The schema is valid per the Avro specification. Recursive types via named references are
  explicitly allowed.
• The panic occurs during schema parsing (ParseType), not during marshal/unmarshal.
• The panic occurs regardless of the Go target struct — even if the Go struct has no
  corresponding field for the problematic schema field, the full schema tree is still
  analyzed.
• Schemas with simple unions (e.g., ["null", "string"]) or non-recursive records work
  fine. The issue is specifically with recursive named type references inside multi-branch
  unions.

Expected Behavior

avro.ParseType() should either:

1. Successfully parse the schema and handle recursive type references during analysis, OR
2. Return an error describing the unsupported pattern (instead of panicking)