Tests: Pin augmented assignment on struct fields and the shadowing error

A struct-field test with a non-add operator and a sub-64-bit field (the
narrow-on-store path), and a strict expected failure for counter += 1 without
a global statement, which now fails as loudly as plain assignment does. Ruff
flags that line as F823 (referenced before assignment) -- the same
UnboundLocalError Python itself would raise, which is exactly the semantics
the global statement requirement mirrors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01L1PX8EuP9C3o3veWGA84RF

Author: r41k0u

tests/failing_tests/globals_augassign_shadowing.py

@@ -0,0 +1,28 @@
+# `counter += 1` without `global counter` must be the same loud error as plain
+# assignment. Before direct lowering this slipped past the allocation pass
+# (which only walks Assign) and failed later with a misleading message.
+from pythonbpf import bpf, section, bpfglobal, compile
+from ctypes import c_void_p, c_int64, c_uint64
+
+
+@bpf
+@bpfglobal
+def counter() -> c_uint64:
+    return c_uint64(0)
+
+
+@bpf
+@section("tracepoint/raw_syscalls/sys_enter")
+def prog(ctx: c_void_p) -> c_int64:
+    counter += 1  # noqa: F823, F841 -- missing `global counter` on purpose; this is
+    # the UnboundLocalError shape, and the compiler must reject it just as loudly
+    return c_int64(0)
+
+
+@bpf
+@bpfglobal
+def LICENSE() -> str:
+    return "GPL"
+
+
+compile()

tests/passing_tests/assign/augassign_struct_field.py

@@ -0,0 +1,35 @@
+# Augmented assignment to a struct field: one GEP, load, op, store. Also a
+# non-add operator and a sub-64-bit field, which exercises the narrow-on-store
+# path of the direct lowering.
+from pythonbpf import bpf, section, bpfglobal, compile, struct
+from ctypes import c_void_p, c_int64, c_uint64, c_uint32
+
+
+@bpf
+@struct
+class data_t:
+    pid: c_uint64
+    hits: c_uint32
+
+
+@bpf
+@section("tracepoint/raw_syscalls/sys_enter")
+def prog(ctx: c_void_p) -> c_int64:
+    x = 5
+    x -= 1
+    dat = data_t()
+    dat.pid = 10
+    dat.pid += x
+    dat.hits = 1
+    dat.hits <<= 2
+    print(f"pid {dat.pid} hits {dat.hits} x {x}")
+    return c_int64(0)
+
+
+@bpf
+@bpfglobal
+def LICENSE() -> str:
+    return "GPL"
+
+
+compile()

tests/test_config.toml

@@ -38,3 +38,5 @@
 "failing_tests/globals_undeclared_name.py" = {reason = "`global x` naming something that is not a @bpfglobal is a compile error", level = "ir"}
 
 "failing_tests/globals_bad_type.py" = {reason = "Non-integer-scalar globals are not supported in milestone 1 (NotImplementedError by design)", level = "ir"}
+
+"failing_tests/globals_augassign_shadowing.py" = {reason = "Augmented assignment to a global name without a `global` statement is a deliberate compile error (would shadow the BPF global)", level = "ir"}