# system/assertions

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This module provides various assertion utilities.

Note: This module is reexported by `system` and thus does not need to be imported directly (with `system/assertions`).

# Imports

miscdollars

# Procs

    proc failedAssertImpl(msg: string) {....raises: [], tags: [].}

  Raises an `AssertionDefect` with `msg`, but this is hidden from the effect system. Called when an assertion failed. Source Edit

    proc raiseAssert(msg: string) {.noinline, noreturn, nosinks, ...raises: [],
                                    tags: [].}

  Raises an `AssertionDefect` with `msg`. Source Edit

# Templates

    template assert(cond: untyped; msg = "")

  Raises `AssertionDefect` with `msg` if `cond` is false. Note that `AssertionDefect` is hidden from the effect system, so it doesn't produce `{.raises: [AssertionDefect].}`. This exception is only supposed to be caught by unit testing frameworks.

  No code will be generated for `assert` when passing `-d:danger` (implied by `--assertions:off`). See command line switches.

  Example:

      assert 1 == 1

  Example: cmd: --assertions:off

      assert 1 == 2 # no code generated, no failure here

  Example: cmd: -d:danger

      assert 1 == 2 # ditto

  Source Edit

    template doAssert(cond: untyped; msg = "")

  Similar to assert but is always turned on regardless of `--assertions`.

  Example:

      doAssert 1 == 1 # generates code even when built with `-d:danger` or `--assertions:off`

  Source Edit

    template doAssertRaises(exception: typedesc; code: untyped)

  Raises `AssertionDefect` if specified `code` does not raise `exception`.

  Example:

      doAssertRaises(ValueError): raise newException(ValueError, "Hello World")
      doAssertRaises(CatchableError): raise newException(ValueError, "Hello World")
      doAssertRaises(AssertionDefect): doAssert false

  Source Edit

    template onFailedAssert(msg, code: untyped): untyped {.dirty.}

  Sets an assertion failure handler that will intercept any assert statements following `onFailedAssert` in the current scope.

  Example:

      type MyError = object of CatchableError
        lineinfo: tuple[filename: string, line: int, column: int]
      # block-wide policy to change the failed assert exception type in order to
      # include a lineinfo
      onFailedAssert(msg):
        raise (ref MyError)(msg: msg, lineinfo: instantiationInfo(-2))
      doAssertRaises(MyError): doAssert false

  Source Edit