MIR

• Functions contain basic blocks.
• Blocks contain statements and end in one terminator.
• _0 is the return slot.
• Places identify locals plus field, index, deref, or downcast projections.
• Rvalues describe computations that assign into places.

Lowering to MIR replaces nested syntax with a graph. That graph is where later passes can reason about reachability, liveness, drops, and borrow precision without guessing how source syntax might execute.

• if becomes conditional terminators and join blocks.
• Loops become back-edges.
• break value writes to a loop result place.
• Function calls become call terminators with success continuations.

• Literals and booleans can lower to switch-like tests.
• Ranges become comparison chains.
• Enum variants read discriminants and downcast payloads.
• Guards run after a structural match succeeds.
• Unsupported patterns should bail honestly until implemented.

• Consuming reads become Move operands.
• Borrowing reads remain non-consuming.
• Owned locals get drops at scope exits.
• Moved-out locals are skipped so values are not dropped twice.
• Conditional moves and partial moves need later drop-flag precision.