Assert Function
Noir includes a special assert
function which will explicitly constrain the predicate/comparison
expression that follows to be true. If this expression is false at runtime, the program will fail to
be proven. Example:
fn main(x : Field, y : Field) {
assert(x == y);
}
Assertions only work for predicate operations, such as
==
. If there's any ambiguity on the operation, the program will fail to compile. For example, it is unclear ifassert(x + y)
would check forx + y == 0
or simply would returntrue
.
You can optionally provide a message to be logged when the assertion fails:
assert(x == y, "x and y are not equal");
Aside string literals, the optional message can be a format string or any other type supported as input for Noir's print functions. This feature lets you incorporate runtime variables into your failed assertion logs:
assert(x == y, f"Expected x == y, but got {x} == {y}");
Using a variable as an assertion message directly:
struct myStruct {
myField: Field
}
let s = myStruct { myField: y };
assert(s.myField == x, s);