// RUN: %ProtectFileCheckOutput 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
// RUN: %ProtectFileCheckOutput not FileCheck -check-prefix=REPEAT -check-prefix=REPEAT -input-file %s %s 2>&1 | FileCheck -check-prefix=DUPLICATE_PREFIX %s
// RUN: %ProtectFileCheckOutput not FileCheck -check-prefix=VALID -check-prefix=A! -input-file %s %s 2>&1 | FileCheck -check-prefix=BAD_PREFIX %s
// RUN: %ProtectFileCheckOutput not FileCheck -check-prefix= -input-file %s %s 2>&1 | FileCheck -check-prefix=EMPTY_PREFIX %s
foobar
; A1a-B_c: foobar

; BAD_PREFIX: supplied check prefix must start with a letter and contain only alphanumeric characters, hyphens, and underscores: 'A!'

; DUPLICATE_PREFIX: error: supplied check prefix must be unique among check and comment prefixes: 'REPEAT'

; EMPTY_PREFIX: error: supplied check prefix must not be the empty string