Definition
Plain language
The automatic check that the pieces of a program fit together according to the language's rules.
As stated in the literature
Static verification that an expression conforms to a type system; in Lean, definitions always type-check, which agents exploit to encode an unproven theorem as a definition and pass the kernel without proving anything.
Also called: type-checks, type-checking
Why it matters: It catches structural mistakes automatically, though in some systems it can be misused to slip an unproven claim past the checker.
For example, this check catches when you try to add a number to a piece of text, flagging that the pieces don't fit the language's rules.
Heard on the show
“The lie dies at the type-check.”Episode 067 — An AI Just Solved a 1996 Erdős Problem—and the Simplest Agent Won