definite assignment: reading a local before it is initialized is a compile error (spec 4.1.5, b.1.9)

track linited per local alongside the ownership state; snapshots, exit records and joins carry it, and a join keeps a local set only when every reaching path set it. x = e, a declaration initializer, &x (out-parameter), a full array initializer, or using an aggregate as an address set a local; field and element writes do not set the aggregate. while/for bodies that may run zero times do not count; do/while does. compiler, runtime, std, actor and lsp sources initialize the locals the rule flagged; zc0 accepts = {} brace lists (zeroed). tests: tests/errors/uninit_*.zc, tests/conformance/4-statements/uninit_*.zc

1 files changed, 1 insertions, 1 deletions

diff --git a/docs/LEARN.md b/docs/LEARN.md
index 081498d..e4fcdc6 100644
--- a/docs/LEARN.md
+++ b/docs/LEARN.md
@@ -63,7 +63,7 @@ hello, world!
 
 ### variables and while
 
-`let` infers a variable's type from its initializer. an integer literal stays a plain word. `int i = 0;` writes the type explicitly. the lifetime analyzer runs by default; the optional typechecker is enabled separately with `typecheck on;`.
+`let` infers a variable's type from its initializer. an integer literal stays a plain word. `int i = 0;` writes the type explicitly. a local must be assigned on every path before it is read (locals are not zeroed); passing `&x` counts as initializing `x`, and an array or struct needs a full `{...}` initializer or `&agg`. the lifetime analyzer runs by default; the optional typechecker is enabled separately with `typecheck on;`.
 
 `while` tests before entering the body. `i++` increments the variable, and `break` leaves the loop.