Statements

Bindings

Type x = expression;          // immutable
@residual Type y = expression; // treated as unknown while compiling
_ = expression;               // evaluate, discard
Point { x, y } = p;           // destructure a record
Some(v) = opt;                // irrefutable only: an error if it can fail

A name is bound once in its scope and never shadowed, including by nested blocks, parameters and pattern bindings.

Control

• if (c) stmt else stmt, if (Pattern = e) { ... } (if-let)
• while (c) { ... }, while (Pattern = e) { ... } (while-let)
• for (Type x in e) { ... } over a range or a list
• break;, continue;, return e;

Every path through a function that returns a value must end in return (or abort through todo / unimplemented); the compiler rejects a function that can fall off its end.

Handles

with (File f = filesystem.open(path)) {
    Str text = filesystem.read_handle(f);
}

with binds one or more handles and closes them at the end of the block.

Assertions and debugging

assert(c, "msg"), rt_assert(c, "msg"), known(x), rt_known(x), comptime_print(e), todo("msg"), unimplemented("msg"). SourceLoc here = #location; captures the current source location.