booleans, comparisons, and if/else

TODO.md

@@ -81,10 +81,14 @@
   - static inline functions (implemented)
 
 - 5. control flow
-  - boolean expressions
+  - boolean expressions (implemented)
+    - `bool` type with `true` / `false` literals
+    - comparison operators: `==`, `!=`, `<`, `<=`, `>`, `>=` (numeric operands widen; `bool` supports only `==` / `!=`)
     - operators: `and`, `or`, `!`
     - lazy evaluation / short-circuit evaluation
-  - if statements. example: `if condition { ... } else if { ... } else { ... }`
+  - if statements (implemented). example: `if condition { ... } else if { ... } else { ... }`
+    - conditions must be `bool`; block-scoped locals with shadowing across blocks
+    - lowered through new `Label` / `Br` / `Cond_Br` IR opcodes (alloca-backed locals, no phi nodes)
   - conditional unwrapping for optionals (`?T`): `if val |v| { ... } else { ... }` - unwrap `val` into `v` if it is not `none`
   - conditional unwrapping with guard clause:  `if val |v : v >= 10| { ... } else { ... }` - unwrap `val` into `v` if it is not `none`
   - multi-unwrap (see section below)