Phase 11 just introduced compound assign lowering on submain, pulling += , -= , *= , /= , and %%= into the IR backend. All in all, 126 new lines in src/ir/lower.rs and three fresh tests. These operators mark their maiden voyage through the IR backend, and while main keeps its 78/78 green tests, submain stays ahead by 22 commits with a 33-day bridge to cross. Compound Assign Lowering Commit 9015aff on submain is the sentinel. Gone is the CompoundAssign stub that only returned an UnresolvedSemanticArtifact . Now, it has real weight with true lowering logic. For Binding LValues, it mirrors the plain assignment's SSA journey: Fetch the SSA value of the binding. Lower the right-hand argument. Emit a Binary instruction mapping to the op ( Add for += , Sub for -= , etc.). Re-bind via SsaBind and adjust the binding map. For DotAccess LValues, things are different. Instead of silently bypassing, compound assigns for struct fields raise an intentional typed error.…