Assertions

assert is a statement that checks a Boolean condition at runtime. If the condition is true, execution continues silently. If it is false, the program panics immediately with a descriptive failure message.

let x = 42
assert x > 0          // passes. Silent
assert x == 42        // passes. Silent

Syntax

assert <expr>

The expression must be of type Bool. The checker rejects any other type at compile time (error E100).

assert true           // ok
assert 1 == 1         // ok
assert "hello"        // E100: type mismatch. Expected Bool, found String

Failure messages

When an assertion fails, Vertex prints a rich message that includes:

The source location (file, line, column).
The rendered source of the condition.
For comparison operators (==, !=, <, >, <=, >=): the actual values of the left-hand and right-hand sides.

Comparison failure example:

assertion failed at examples/jit/lang/assertions.vtx:7:1
  source:   x == 42
  left:     5
  right:    42

Non-comparison failure example:

assertion failed at examples/jit/lang/assertions.vtx:11:1
  source:   list.contains(target)

`assert` vs `let assert`

These are two distinct constructs that share the assert keyword:

	`assert`	`let assert`
Purpose	Check a Bool invariant	Destructure a value that must match a pattern
Form	`assert expr`	`let assert Pat = expr`
Failure message	`assertion failed: …`	`let assert pattern did not match: …`

Both cause a panic on failure and are appropriate during development and in tests.

Apex codegen

assert expr compiles to System.Assert.isTrue(expr, 'assertion failed at …'). The message is a compile-time string. No runtime decomposition occurs on the Apex side. Assertions are never stripped from emitted Apex; there is no release-build mode that removes them.