Fixes#1358
The compiler was attempting to compile methods for non-instantiated generic
types (like unique.Handle[T]), which caused the SSA builder to panic with a
nil pointer dereference. This fix adds two checks:
1. In compileType: Skip generic type definitions (types with type parameters
but no type arguments)
2. In compileMethods: Skip types containing type parameters and skip methods
from external packages
The unique.Make demo now compiles without panicking, though it still requires
runtime support for the unique package to link successfully.
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Co-authored-by: cpunion <cpunion@users.noreply.github.com>
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