[jogibear9988]

Mutating a struct through Unbox can update a temporary instead of the boxed value. Emit an unbox address for writable storage contexts and ref arguments, while preserving value copies for ordinary reads and Convert, plus nullable/null/type-check behavior.

Validation

The focused regression reproduces a failure or crash on master a0950432 and passes with this change. Release solution build passes with zero warnings/errors. Both Standard and LightExpression native suites run.

Runtime	TestX passed	Legacy passed
.NET 10	363	1,756
.NET 8	363	1,755
.NET Framework 4.7.2	344	1,639

Measurements

Compare master a0950432 with this commit 8f66d7ac. Windows ARM64, Release; .NET 8.0.28 and 10.0.9. Compilation uses prebuilt trees; invocation uses precompiled delegates and excludes expression construction/compilation. Standard and LightExpression are measured separately.

Two fresh process rounds reverse version-loading order, pin execution to one logical CPU, disable tiered compilation, warm both versions, and alternate measurement order. Values below are medians across 14 samples per side (seven per round; 30 ms calibration target).

Compilation allocation changes on the listed affected controls: -8 B/op. Other measured compilation allocations match master. Invocation allocations match master on every control. Delegate IL changes on unbox_read; the other control IL matches master.

Identical-master control runs also varied: compilation -15.2% to +23.4%, invocation -21.5% to +8.9%. Timings below are observations, not a speedup or universal performance-neutrality claim. Cases that fail or produce invalid IL on master have no meaningful before/after invocation ratio; the table uses executable controls that return the expected result in both versions. Framework correctness is tested above; its performance is not measured here.

All table pairs are master → this change. B/op is allocated bytes per operation.

.NET / API	Control	Compile ns/op	Compile B/op	Invoke ns/op	Invoke B/op
10 / Light	add_control	2,521 → 2,515	872 → 872	1.94 → 1.99	0 → 0
10 / Light	convert_copy	2,875 → 2,782	936 → 936	2.20 → 2.17	0 → 0
10 / Light	unbox_read	3,048 → 3,585	936 → 928	2.19 → 2.24	0 → 0
10 / Standard	add_control	3,260 → 3,110	872 → 872	1.91 → 1.92	0 → 0
10 / Standard	convert_copy	6,597 → 4,208	936 → 936	2.30 → 2.29	0 → 0
10 / Standard	unbox_read	3,282 → 3,322	936 → 928	2.26 → 2.24	0 → 0
8 / Light	add_control	990 → 990	872 → 872	1.97 → 2.02	0 → 0
8 / Light	convert_copy	1,001 → 1,109	936 → 936	2.39 → 2.21	0 → 0
8 / Light	unbox_read	1,050 → 1,034	936 → 928	2.22 → 2.23	0 → 0
8 / Standard	add_control	1,019 → 1,030	872 → 872	1.93 → 1.94	0 → 0
8 / Standard	convert_copy	1,126 → 1,314	936 → 936	2.20 → 2.26	0 → 0
8 / Standard	unbox_read	1,163 → 1,143	936 → 928	2.26 → 2.31	0 → 0