| ObjectiveC | Distribution.Simple.CCompiler | 
| ObjectiveCPlusPlus | Distribution.Simple.CCompiler | 
| objExtension | Distribution.Simple.BuildPaths | 
| OCaml_LGPL_linking_exception | Distribution.SPDX.LicenseExceptionId, Distribution.SPDX | 
| OCCT_exception_1_0 | Distribution.SPDX.LicenseExceptionId, Distribution.SPDX | 
| OCCT_PL | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OCLC_2_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| octDigit | Distribution.Compat.CharParsing | 
| ODbL_1_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| ODC_By_1_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| odd | Distribution.Compat.Prelude.Internal | 
| OFL_1_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OFL_1_0_no_RFN | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OFL_1_0_RFN | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OFL_1_1 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OFL_1_1_no_RFN | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OFL_1_1_RFN | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OGC_1_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OGL_Canada_2_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OGL_UK_1_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OGL_UK_2_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OGL_UK_3_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OGTSL | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_1_1 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_1_2 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_1_3 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_1_4 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_0_1 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_1 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_2 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_2_1 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_2_2 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_3 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_4 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_5 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_6 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_7 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OLDAP_2_8 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| oldExtensions |  | 
| 1 (Function) | Distribution.Types.BuildInfo, Distribution.PackageDescription | 
| 2 (Function) | Distribution.Types.BuildInfo.Lens, Distribution.Types.Lens | 
| OML | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| on | Distribution.Compat.Prelude.Internal | 
| OneComponentRequestedSpec | Distribution.Types.ComponentRequestedSpec | 
| oneOf | Distribution.Compat.CharParsing | 
| OpenBrace | Distribution.Fields.Lexer | 
| OpenBSD | Distribution.System | 
| OpenJDK_assembly_exception_1_0 | Distribution.SPDX.LicenseExceptionId, Distribution.SPDX | 
| OpenModule |  | 
| 1 (Type/Class) | Distribution.Backpack | 
| 2 (Data Constructor) | Distribution.Backpack | 
| openModuleFreeHoles | Distribution.Backpack | 
| OpenModuleSubst | Distribution.Backpack | 
| openModuleSubstFreeHoles | Distribution.Backpack | 
| OpenModuleVar | Distribution.Backpack | 
| OpenSSL | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OpenUnitId | Distribution.Backpack | 
| openUnitIdFreeHoles | Distribution.Backpack | 
| Openvpn_openssl_exception | Distribution.SPDX.LicenseExceptionId, Distribution.SPDX | 
| OPL_1_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OptArg | Distribution.Simple.Command | 
| optArg | Distribution.Simple.Command | 
| optArg' | Distribution.Simple.Command | 
| OptDescr | Distribution.Simple.Command | 
| OptFlags | Distribution.Simple.Command | 
| OptimisationLevel | Distribution.Simple.Compiler, Distribution.Simple | 
| option |  | 
| 1 (Function) | Distribution.Compat.Parsing, Distribution.Compat.CharParsing | 
| 2 (Function) | Distribution.Simple.Command | 
| Option' |  | 
| 1 (Type/Class) | Distribution.Compat.Semigroup | 
| 2 (Data Constructor) | Distribution.Compat.Semigroup | 
| optional | Distribution.Compat.Parsing, Distribution.Compat.CharParsing | 
| optionalField | Distribution.FieldGrammar.Class, Distribution.FieldGrammar | 
| optionalFieldAla | Distribution.FieldGrammar.Class, Distribution.FieldGrammar | 
| optionalFieldDef | Distribution.FieldGrammar.Class, Distribution.FieldGrammar | 
| optionalFieldDefAla | Distribution.FieldGrammar.Class, Distribution.FieldGrammar | 
| OptionBool | Distribution.TestSuite | 
| optionDefault | Distribution.TestSuite | 
| OptionDescr |  | 
| 1 (Type/Class) | Distribution.TestSuite | 
| 2 (Data Constructor) | Distribution.TestSuite | 
| optionDescr | Distribution.Simple.Command | 
| optionDescription | Distribution.TestSuite | 
| optionDistPref | Distribution.Simple.Setup | 
| OptionEnum | Distribution.TestSuite | 
| OptionField |  | 
| 1 (Type/Class) | Distribution.Simple.Command | 
| 2 (Data Constructor) | Distribution.Simple.Command | 
| OptionFile | Distribution.TestSuite | 
| optionFileExtensions | Distribution.TestSuite | 
| optionFileIsDir | Distribution.TestSuite | 
| optionFileMustExist | Distribution.TestSuite | 
| optionName |  | 
| 1 (Function) | Distribution.TestSuite | 
| 2 (Function) | Distribution.Simple.Command | 
| OptionNumber | Distribution.TestSuite | 
| optionNumberBounds | Distribution.TestSuite | 
| optionNumberIsInt | Distribution.TestSuite | 
| optionNumJobs | Distribution.Simple.Setup | 
| OptionRngSeed | Distribution.TestSuite | 
| Options | Distribution.TestSuite | 
| options |  | 
| 1 (Function) | Distribution.TestSuite | 
| 2 (Function) | Distribution.Types.BuildInfo, Distribution.PackageDescription | 
| 3 (Function) | Distribution.Types.BuildInfo.Lens, Distribution.Types.Lens | 
| OptionSet | Distribution.TestSuite | 
| OptionString | Distribution.TestSuite | 
| optionStringMultiline | Distribution.TestSuite | 
| OptionType | Distribution.TestSuite | 
| optionType | Distribution.TestSuite | 
| optionVerbosity | Distribution.Simple.Setup | 
| optKeepTempFiles | Distribution.Simple.Utils | 
| or | Distribution.Compat.Prelude.Internal | 
| Ord | Distribution.Compat.Prelude.Internal | 
| ord | Distribution.Compat.Prelude.Internal | 
| Ordering | Distribution.Compat.Prelude.Internal | 
| Ordinary | Distribution.Simple.InstallDirs.Internal | 
| ordNub | Distribution.Utils.Generic, Distribution.Simple.Utils | 
| ordNubBy | Distribution.Utils.Generic, Distribution.Simple.Utils | 
| ordNubRight | Distribution.Utils.Generic, Distribution.Simple.Utils | 
| OrEarlierVersion | Distribution.Types.VersionRange.Internal | 
| orEarlierVersion | Distribution.Types.VersionRange.Internal, Distribution.Types.VersionRange, Distribution.Version, Distribution.Simple | 
| OrEarlierVersionF | Distribution.Types.VersionRange.Internal, Distribution.Types.VersionRange, Distribution.Version, Distribution.Simple | 
| OrLaterVersion | Distribution.Types.VersionRange.Internal | 
| orLaterVersion | Distribution.Types.VersionRange.Internal, Distribution.Types.VersionRange, Distribution.Version, Distribution.Simple | 
| OrLaterVersionF | Distribution.Types.VersionRange.Internal, Distribution.Types.VersionRange, Distribution.Version, Distribution.Simple | 
| OS |  | 
| 1 (Type/Class) | Distribution.System | 
| 2 (Data Constructor) | Distribution.Types.ConfVar, Distribution.Types.GenericPackageDescription.Lens, Distribution.Types.Lens, Distribution.PackageDescription | 
| OSET_PL_2_1 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OSL_1_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OSL_1_1 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OSL_2_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OSL_2_1 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OSL_3_0 | Distribution.SPDX.LicenseId, Distribution.SPDX | 
| OSVar | Distribution.Simple.InstallDirs.Internal, Distribution.Simple.InstallDirs, Distribution.Simple.LocalBuildInfo | 
| OSX | Distribution.System | 
| OtherArch | Distribution.System | 
| OtherCompiler | Distribution.Compiler, Distribution.Simple.Compiler, Distribution.Simple | 
| otherExtensions |  | 
| 1 (Function) | Distribution.Types.BuildInfo, Distribution.PackageDescription | 
| 2 (Function) | Distribution.Types.BuildInfo.Lens, Distribution.Types.Lens | 
| otherLanguages |  | 
| 1 (Function) | Distribution.Types.BuildInfo, Distribution.PackageDescription | 
| 2 (Function) | Distribution.Types.BuildInfo.Lens, Distribution.Types.Lens | 
| OtherLicense | Distribution.License, Distribution.Make, Distribution.Simple | 
| otherModules |  | 
| 1 (Function) | Distribution.Types.BuildInfo, Distribution.PackageDescription | 
| 2 (Function) | Distribution.Types.BuildInfo.Lens, Distribution.Types.Lens | 
| OtherOS | Distribution.System | 
| OtherRepoType | Distribution.Types.SourceRepo, Distribution.PackageDescription | 
| otherwise | Distribution.Compat.Prelude.Internal | 
| over | Distribution.Compat.Lens | 
| OverlappingInstances | Language.Haskell.Extension, Distribution.Simple | 
| OverloadedLabels | Language.Haskell.Extension, Distribution.Simple | 
| OverloadedLists | Language.Haskell.Extension, Distribution.Simple | 
| OverloadedStrings | Language.Haskell.Extension, Distribution.Simple | 
| overNubList | Distribution.Utils.NubList | 
| overNubListR | Distribution.Utils.NubList | 
| O_UDA_1_0 | Distribution.SPDX.LicenseId, Distribution.SPDX |