fix compilation on old compilers #204

Job	Run time
Run all tests (dmd-latest, dmd, ubuntu-22.04, make)	2m 21s
Run all tests (dmd-latest, dmd, ubuntu-22.04, dub, current)	1m 35s
Run all tests (dmd-latest, dmd, ubuntu-22.04, dub, min libdparse)	1m 15s
Run all tests (dmd-latest, dmd, macos-latest, make)	10m 23s
Run all tests (dmd-latest, dmd, macos-latest, dub, current)	2m 7s
Run all tests (dmd-latest, dmd, macos-latest, dub, min libdparse)	1m 31s
Run all tests (dmd-latest, dmd, windows-latest, make)	2m 13s
Run all tests (dmd-latest, dmd, windows-latest, dub, current)	2m 28s
Run all tests (dmd-latest, dmd, windows-latest, dub, min libdparse)	2m 46s
Run all tests (ldc-latest, ldmd2, ubuntu-22.04, make)	2m 55s
Run all tests (ldc-latest, ldmd2, ubuntu-22.04, dub, current)	1m 43s
Run all tests (ldc-latest, ldmd2, ubuntu-22.04, dub, min libdparse)	1m 42s
Run all tests (ldc-latest, ldmd2, macos-latest, make)	23m 50s
Run all tests (ldc-latest, ldmd2, macos-latest, dub, current)	2m 17s
Run all tests (ldc-latest, ldmd2, macos-latest, dub, min libdparse)	2m 46s
Run all tests (ldc-latest, ldmd2, windows-latest, make)	6m 7s
Run all tests (ldc-latest, ldmd2, windows-latest, dub, current)	3m 35s
Run all tests (ldc-latest, ldmd2, windows-latest, dub, min libdparse)	3m 32s
Run all tests (dmd-latest, gdc-12, ubuntu-22.04, make)	6m 42s
	1h 21m 48s

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