// RUN: not FileCheck -check-prefix=A! -input-file %s %s 2>&1 | FileCheck -check-prefix=BAD_PREFIX %s
// RUN: FileCheck -check-prefix=A1a-B_c -input-file %s %s

foobar
; A1a-B_c: foobar

; BAD_PREFIX: Supplied check-prefix is invalid! Prefixes must start with a letter and contain only alphanumeric characters, hyphens and underscores
