ghc-9.2.1: The GHC API
Safe HaskellSafe-Inferred



Unit manipulation



Reading the package config, and processing cmdline args

data UnitState Source #




  • unitInfoMap :: UnitInfoMap

    A mapping of Unit to UnitInfo. This list is adjusted so that only valid units are here. UnitInfo reflects what was stored *on disk*, except for the trusted flag, which is adjusted at runtime. (In particular, some units in this map may have the exposed flag be False.)

  • preloadClosure :: PreloadUnitClosure

    The set of transitively reachable units according to the explicitly provided command line arguments. A fully instantiated VirtUnit may only be replaced by a RealUnit from this set. See Note [VirtUnit to RealUnit improvement]

  • packageNameMap :: UniqFM PackageName IndefUnitId

    A mapping of PackageName to IndefUnitId. This is used when users refer to packages in Backpack includes.

  • wireMap :: Map UnitId UnitId

    A mapping from database unit keys to wired in unit ids.

  • unwireMap :: Map UnitId UnitId

    A mapping from wired in unit ids to unit keys from the database.

  • preloadUnits :: [UnitId]

    The units we're going to link in eagerly. This list should be in reverse dependency order; that is, a unit is always mentioned before the units it depends on.

  • explicitUnits :: [Unit]

    Units which we explicitly depend on (from a command line flag). We'll use this to generate version macros.

  • moduleNameProvidersMap :: !ModuleNameProvidersMap

    This is a full map from ModuleName to all modules which may possibly be providing it. These providers may be hidden (but we'll still want to report them in error messages), or it may be an ambiguous import.

  • pluginModuleNameProvidersMap :: !ModuleNameProvidersMap

    A map, like moduleNameProvidersMap, but controlling plugin visibility.

  • requirementContext :: Map ModuleName [InstantiatedModule]

    A map saying, for each requirement, what interfaces must be merged together when we use them. For example, if our dependencies are p[A=<A>] and q[A=<A>,B=r[C=<A>]:B], then the interfaces to merge for A are p[A=<A>]:A, q[A=<A>,B=r[C=<A>]:B]:A and r[C=<A>]:C.

    There's an entry in this map for each hole in our home library.

  • allowVirtualUnits :: !Bool

    Indicate if we can instantiate units on-the-fly.

    This should only be true when we are type-checking an indefinite unit. See Note [About units] in GHC.Unit.

data UnitDatabase unit Source #

Unit database

initUnits :: Logger -> DynFlags -> Maybe [UnitDatabase UnitId] -> IO ([UnitDatabase UnitId], UnitState, HomeUnit, Maybe PlatformConstants) Source #

Read the unit database files, and sets up various internal tables of unit information, according to the unit-related flags on the command-line (-package, -hide-package etc.)

initUnits can be called again subsequently after updating the packageFlags field of the DynFlags, and it will update the unitState in DynFlags.

readUnitDatabases :: (Int -> SDoc -> IO ()) -> UnitConfig -> IO [UnitDatabase UnitId] Source #

readUnitDatabase :: (Int -> SDoc -> IO ()) -> UnitConfig -> FilePath -> IO (UnitDatabase UnitId) Source #

getUnitDbRefs :: UnitConfig -> IO [PkgDbRef] Source #

resolveUnitDatabase :: UnitConfig -> PkgDbRef -> IO (Maybe FilePath) Source #

Return the path of a package database from a PkgDbRef. Return Nothing when the user database filepath is expected but the latter doesn't exist.

NB: This logic is reimplemented in Cabal, so if you change it, make sure you update Cabal. (Or, better yet, dump it in the compiler info so Cabal can use the info.)

listUnitInfo :: UnitState -> [UnitInfo] Source #

Get a list of entries from the unit database. NB: be careful with this function, although all units in this map are "visible", this does not imply that the exposed-modules of the unit are available (they may have been thinned or renamed).

Querying the package config

lookupUnit :: UnitState -> Unit -> Maybe UnitInfo Source #

Find the unit we know about with the given unit, if any

lookupUnit' :: Bool -> UnitInfoMap -> PreloadUnitClosure -> Unit -> Maybe UnitInfo Source #

A more specialized interface, which doesn't require a UnitState (so it can be used while we're initializing DynFlags)

Parameters: * a boolean specifying whether or not to look for on-the-fly renamed interfaces * a UnitInfoMap * a PreloadUnitClosure

unsafeLookupUnit :: HasDebugCallStack => UnitState -> Unit -> UnitInfo Source #

Looks up the given unit in the unit state, panicing if it is not found

lookupUnitId :: UnitState -> UnitId -> Maybe UnitInfo Source #

Find the unit we know about with the given unit id, if any

lookupUnitId' :: UnitInfoMap -> UnitId -> Maybe UnitInfo Source #

Find the unit we know about with the given unit id, if any

unsafeLookupUnitId :: HasDebugCallStack => UnitState -> UnitId -> UnitInfo Source #

Looks up the given unit id in the unit state, panicing if it is not found

lookupPackageName :: UnitState -> PackageName -> Maybe IndefUnitId Source #

Find the unit we know about with the given package name (e.g. foo), if any (NB: there might be a locally defined unit name which overrides this)

improveUnit :: UnitState -> Unit -> Unit Source #

Given a fully instantiated InstantiatedUnit, improve it into a RealUnit if we can find it in the package database.

searchPackageId :: UnitState -> PackageId -> [UnitInfo] Source #

Search for units with a given package ID (e.g. "foo-0.1")

lookupModuleInAllUnits :: UnitState -> ModuleName -> [(Module, UnitInfo)] Source #

Takes a ModuleName, and if the module is in any package returns list of modules which take that name.

lookupModulePackage :: UnitState -> ModuleName -> Maybe FastString -> Maybe [UnitInfo] Source #

The package which the module **appears** to come from, this could be the one which reexports the module from it's original package. This function is currently only used for -Wunused-packages

requirementMerges :: UnitState -> ModuleName -> [InstantiatedModule] Source #

Return this list of requirement interfaces that need to be merged to form mod_name, or [] if this is not a requirement.

data LookupResult Source #

The result of performing a lookup


LookupFound Module (UnitInfo, ModuleOrigin)

Found the module uniquely, nothing else to do

LookupMultiple [(Module, ModuleOrigin)]

Multiple modules with the same name in scope

LookupHidden [(Module, ModuleOrigin)] [(Module, ModuleOrigin)]

No modules found, but there were some hidden ones with an exact name match. First is due to package hidden, second is due to module being hidden

LookupUnusable [(Module, ModuleOrigin)]

No modules found, but there were some unusable ones with an exact name match

LookupNotFound [ModuleSuggestion]

Nothing found, here are some suggested different names

data ModuleOrigin Source #

Given a module name, there may be multiple ways it came into scope, possibly simultaneously. This data type tracks all the possible ways it could have come into scope. Warning: don't use the record functions, they're partial!



Module is hidden, and thus never will be available for import. (But maybe the user didn't realize), so we'll still keep track of these modules.)

ModUnusable UnusableUnitReason

Module is unavailable because the package is unusable.


Module is public, and could have come from some places.


  • fromOrigUnit :: Maybe Bool

    Just False means that this module is in someone's exported-modules list, but that package is hidden; Just True means that it is available; Nothing means neither applies.

  • fromExposedReexport :: [UnitInfo]

    Is the module available from a reexport of an exposed package? There could be multiple.

  • fromHiddenReexport :: [UnitInfo]

    Is the module available from a reexport of a hidden package?

  • fromPackageFlag :: Bool

    Did the module export come from a package flag? (ToDo: track more information.

data UnusableUnitReason Source #

The reason why a unit is unusable.



We ignored it explicitly using -ignore-package.

BrokenDependencies [UnitId]

This unit transitively depends on a unit that was never present in any of the provided databases.

CyclicDependencies [UnitId]

This unit transitively depends on a unit involved in a cycle. Note that the list of UnitId reports the direct dependencies of this unit that (transitively) depended on the cycle, and not the actual cycle itself (which we report separately at high verbosity.)

IgnoredDependencies [UnitId]

This unit transitively depends on a unit which was ignored.

ShadowedDependencies [UnitId]

This unit transitively depends on a unit which was shadowed by an ABI-incompatible unit.


Instances details
Outputable UnusableUnitReason Source # 
Instance details

Defined in GHC.Unit.State

closeUnitDeps :: UnitInfoMap -> [(UnitId, Maybe UnitId)] -> MaybeErr UnitErr [UnitId] Source #

Takes a list of UnitIds (and their "parent" dependency, used for error messages), and returns the list with dependencies included, in reverse dependency order (a units appears before those it depends on).

closeUnitDeps' :: UnitInfoMap -> [UnitId] -> [(UnitId, Maybe UnitId)] -> MaybeErr UnitErr [UnitId] Source #

Similar to closeUnitDeps but takes a list of already loaded units as an additional argument.

Module hole substitution

type ShHoleSubst = ModuleNameEnv Module Source #

Substitution on module variables, mapping module names to module identifiers.

renameHoleUnit :: UnitState -> ShHoleSubst -> Unit -> Unit Source #

Substitutes holes in a Unit, suitable for renaming when an include occurs; see Note [Representation of module/name variable].

p[A=<A>] maps to p[A=<B>] with A=<B>.

renameHoleModule :: UnitState -> ShHoleSubst -> Module -> Module Source #

Substitutes holes in a Module. NOT suitable for being called directly on a nameModule, see Note [Representation of module/name variable]. p[A=<A>]:B maps to p[A=q():A]:B with A=q():A; similarly, <A> maps to q():A.

renameHoleUnit' :: UnitInfoMap -> PreloadUnitClosure -> ShHoleSubst -> Unit -> Unit Source #

Like 'renameHoleUnit, but requires only ClosureUnitInfoMap so it can be used by GHC.Unit.State.

renameHoleModule' :: UnitInfoMap -> PreloadUnitClosure -> ShHoleSubst -> Module -> Module Source #

Like renameHoleModule, but requires only ClosureUnitInfoMap so it can be used by GHC.Unit.State.

instUnitToUnit :: UnitState -> InstantiatedUnit -> Unit Source #

Check the database to see if we already have an installed unit that corresponds to the given InstantiatedUnit.

Return a UnitId which either wraps the InstantiatedUnit unchanged or references a matching installed unit.

See Note [VirtUnit to RealUnit improvement]


pprUnits :: UnitState -> SDoc Source #

Show (very verbose) package info

pprUnitsSimple :: UnitState -> SDoc Source #

Show simplified unit info.

The idea is to only print package id, and any information that might be different from the package databases (exposure, trust)

pprUnitIdForUser :: UnitState -> UnitId -> SDoc Source #

Pretty-print a UnitId for the user.

Cabal packages may contain several components (programs, libraries, etc.). As far as GHC is concerned, installed package components ("units") are identified by an opaque IndefUnitId string provided by Cabal. As the string contains a hash, we don't want to display it to users so GHC queries the database to retrieve some infos about the original source package (name, version, component name).

Instead we want to display: packagename-version[:componentname]

Component name is only displayed if it isn't the default library

To do this we need to query a unit database.

pprModuleMap :: ModuleNameProvidersMap -> SDoc Source #

Show the mapping of modules to where they come from.

pprWithUnitState :: UnitState -> SDoc -> SDoc Source #

Print unit-ids with UnitInfo found in the given UnitState


unwireUnit :: UnitState -> Unit -> Unit Source #

Given a wired-in Unit, "unwire" it into the Unit that it was recorded as in the package database.