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Error Flow

Layered Error Model

Nitpick has a three-tier error system:

Tier Mechanism Scope Recovery
Value-level TBB ERR sentinel Arithmetic Check == ERR
Function-level Result pass/fail Function calls ?, ?!, ?|, defaults, catch, drop, raw
Program-level failsafe Fatal errors Must exit(code > 0)

Error Propagation Flow

TBB ERR (value) → Result<T> fail (function) → failsafe (program)
  1. TBB arithmetic — overflow, div-by-zero → ERR sentinel, propagates through pipeline
  2. Function calls — fail errcode → caller must handle Result
  3. Unrecoverable — !!! err → calls failsafe, program exits

The ok Keyword

Allows passing a variable that may have value unknown down the call chain:

ok maybe_unknown_value;

The !!! Operator — Failsafe Shorthand

The !!! operator immediately invokes failsafe with an error code. It is syntactic sugar:

!!! errcode;    →    failsafe(errcode);

Usage

func:validate = int32(int32:input) {
    if (input < 0) {
        !!! 42;     // calls failsafe(42) — program exits
    }
    pass input;
};

func:main = int32() {
    int32:val = raw validate(10);
    exit 0;
};

func:failsafe = int32(tbb32:err) {
    // err == 42 if triggered by !!! above
    exit err => int32;
};

When To Use

Mechanism When Recovery
fail errCode Recoverable error in a function Caller handles Result
?! (emphatic fallback) Result fallback unwrap with emphatic spelling returns value or fallback
catch Error-aware Result fallback handler receives err:int32
!!! errCode Unrecoverable error, bail immediately failsafe receives errCode

Interaction with defer

defer blocks still execute before !!! transfers control to failsafe:

func:cleanup_example = NIL() {
    defer {
        // This runs BEFORE failsafe is called
    };

    !!! 1;   // defer fires, then failsafe(1)
    pass NIL;
};

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