== / != are 4-state and can return x; use === / !== for exact X/Z compare.
bit (2-state) collapses X/Z to 0; logic (4-state) preserves them.
>>> is arithmetic only on signed operands; >> always zero-fills.
Any unsigned operand makes the whole expression unsigned before the operator runs.
$cast checks runtime type; a static handle assignment can compile yet be illegal at runtime.
join resumes after all children; join_any after one; join_none immediately.
Pair join_any/join_none with disable fork or explicit sync or you leak threads.
Nonblocking (<=) updates in the NBA region; read-after-NBA in the same step sees the old value.
Clocking block inputs sample on the previous edge (input skew); outputs drive with output skew.
Constraints solve as a system, not top-to-bottom; order does not imply precedence.
dist := gives each listed value that weight; :/ splits the weight across the range.
solve...before only biases distribution; it never changes the legal solution set.
An over-constrained randomize() returns 0 and leaves variables unchanged.
|-> is overlapped (same cycle); |=> is non-overlapped (next cycle).
An assertion whose antecedent never holds is a vacuous pass, not a real pass.
$past/$rose/$fell sample in the preponed region relative to the assertion clock.
Unreached bins, wrong sample event, or ignore/illegal bins are the usual coverage-closure traps.