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constrained[cond: Bool, msg: StringLiteral = "param assertion failed"]()

Compile time checks that the condition is true.

The constrained is similar to static_assert in C++ and is used to introduce constraints on the enclosing function. In Mojo, the assert places a constraint on the function. The message is displayed when the assertion fails.


  • cond (Bool): The bool value to assert.
  • msg (StringLiteral): The message to display on failure.