Agda.Utils.CallStack

Documentation

data CallStack

CallStacks are a lightweight method of obtaining a partial call-stack at any point in the program.

A function can request its call-site with the HasCallStack constraint. For example, we can define

putStrLnWithCallStack :: HasCallStack => String -> IO ()

as a variant of putStrLn that will get its call-site and print it, along with the string given as argument. We can access the call-stack inside putStrLnWithCallStack with callStack.

>>> :{
putStrLnWithCallStack :: HasCallStack => String -> IO ()
putStrLnWithCallStack msg = do
  putStrLn msg
  putStrLn (prettyCallStack callStack)
:}

Thus, if we call putStrLnWithCallStack we will get a formatted call-stack alongside our string.

>>> putStrLnWithCallStack "hello"
hello
CallStack (from HasCallStack):
  putStrLnWithCallStack, called at <interactive>:... in interactive:Ghci...

GHC solves HasCallStack constraints in three steps:

1. If there is a CallStack in scope -- i.e. the enclosing function has a HasCallStack constraint -- GHC will append the new call-site to the existing CallStack.
2. If there is no CallStack in scope -- e.g. in the GHCi session above -- and the enclosing definition does not have an explicit type signature, GHC will infer a HasCallStack constraint for the enclosing definition (subject to the monomorphism restriction).
3. If there is no CallStack in scope and the enclosing definition has an explicit type signature, GHC will solve the HasCallStack constraint for the singleton CallStack containing just the current call-site.

CallStacks do not interact with the RTS and do not require compilation with -prof. On the other hand, as they are built up explicitly via the HasCallStack constraints, they will generally not contain as much information as the simulated call-stacks maintained by the RTS.

A CallStack is a [(String, SrcLoc)]. The String is the name of function that was called, the SrcLoc is the call-site. The list is ordered with the most recently called function at the head.

NOTE: The intrepid user may notice that HasCallStack is just an alias for an implicit parameter ?callStack :: CallStack. This is an implementation detail and should not be considered part of the CallStack API, we may decide to change the implementation in the future.

Since: base-4.8.1.0

Instances

EmbPrj CallStack

Defined in Agda.TypeChecking.Serialise.Instances.Common

Methods

icode :: CallStack -> S Int32

icod_ :: CallStack -> S Int32

value :: Int32 -> R CallStack

Pretty CallStack

Defined in Agda.Utils.CallStack.Pretty

Methods

pretty :: CallStack -> Doc

prettyPrec :: Int -> CallStack -> Doc

prettyList :: [CallStack] -> Doc

IsList CallStack

Be aware that 'fromList . toList = id' only for unfrozen CallStacks, since toList removes frozenness information.

Since: base-4.9.0.0

Defined in GHC.IsList

Associated Types

type Item CallStack

Methods

fromList :: [Item CallStack] -> CallStack

fromListN :: Int -> [Item CallStack] -> CallStack

toList :: CallStack -> [Item CallStack]

Show CallStack

Since: base-4.9.0.0

Defined in GHC.Show

Methods

showsPrec :: Int -> CallStack -> ShowS

show :: CallStack -> String

showList :: [CallStack] -> ShowS

NFData CallStack

Since: deepseq-1.4.2.0

Defined in Control.DeepSeq

Methods

rnf :: CallStack -> ()

type Item CallStack

Defined in GHC.IsList

type Item CallStack = (String, SrcLoc)

data SrcLoc

A single location in the source code.

Since: base-4.8.1.0

Constructors

SrcLoc

Fields

• srcLocPackage :: [Char]
• srcLocModule :: [Char]
• srcLocFile :: [Char]
• srcLocStartLine :: Int
• srcLocStartCol :: Int
• srcLocEndLine :: Int
• srcLocEndCol :: Int

Instances

EmbPrj SrcLoc

Defined in Agda.TypeChecking.Serialise.Instances.Common

Methods

icode :: SrcLoc -> S Int32

icod_ :: SrcLoc -> S Int32

value :: Int32 -> R SrcLoc

Pretty CallSite

Defined in Agda.Utils.CallStack.Pretty

Methods

pretty :: CallSite -> Doc

prettyPrec :: Int -> CallSite -> Doc

prettyList :: [CallSite] -> Doc

Pretty SrcLoc

Defined in Agda.Utils.CallStack.Pretty

Methods

pretty :: SrcLoc -> Doc

prettyPrec :: Int -> SrcLoc -> Doc

prettyList :: [SrcLoc] -> Doc

Generic SrcLoc

Defined in GHC.Generics

Associated Types

type Rep SrcLoc :: Type -> Type

Methods

from :: SrcLoc -> Rep SrcLoc x

to :: Rep SrcLoc x -> SrcLoc

Show SrcLoc

Since: base-4.9.0.0

Defined in GHC.Show

Methods

showsPrec :: Int -> SrcLoc -> ShowS

show :: SrcLoc -> String

showList :: [SrcLoc] -> ShowS

NFData SrcLoc

Since: deepseq-1.4.2.0

Defined in Control.DeepSeq

Methods

rnf :: SrcLoc -> ()

Eq SrcLoc

Since: base-4.9.0.0

Defined in GHC.Stack.Types

Methods

(==) :: SrcLoc -> SrcLoc -> Bool

(/=) :: SrcLoc -> SrcLoc -> Bool

type Rep SrcLoc

Since: base-4.15.0.0

Defined in GHC.Generics

type Rep SrcLoc = D1 ('MetaData "SrcLoc" "GHC.Stack.Types" "base" 'False) (C1 ('MetaCons "SrcLoc" 'PrefixI 'True) ((S1 ('MetaSel ('Just "srcLocPackage") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [Char]) :*: (S1 ('MetaSel ('Just "srcLocModule") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [Char]) :*: S1 ('MetaSel ('Just "srcLocFile") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [Char]))) :*: ((S1 ('MetaSel ('Just "srcLocStartLine") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Int) :*: S1 ('MetaSel ('Just "srcLocStartCol") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Int)) :*: (S1 ('MetaSel ('Just "srcLocEndLine") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Int) :*: S1 ('MetaSel ('Just "srcLocEndCol") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Int)))))

type HasCallStack = ?callStack :: CallStack

Request a CallStack.

NOTE: The implicit parameter ?callStack :: CallStack is an implementation detail and should not be considered part of the CallStack API, we may decide to change the implementation in the future.

Since: base-4.9.0.0

type SrcLocPackage = String

Type of the package name of a SrcLoc | e.g. `Agda-2.…`

type SrcLocModule = String

Type of the module name of a SrcLoc | e.g. Foo

type SrcFun = String

Type of the name of a function in a CallSite | e.g. proveEverything

type SrcLocFile = String

Type of a filename of a SrcLoc | e.g. `srcfullAgdaUtilsFoo.hs`

type SrcLocLine = Int

Type of a line number of a SrcLoc

type SrcLocCol = Int

Type of a column of a SrcLoc

type CallSite = (SrcFun, SrcLoc)

Type of an entry in a CallStack

type CallSiteFilter = CallSite -> Bool

Type of a filter for CallSite

callStack :: HasCallStack => CallStack

Return the current CallStack.

Does *not* include the call-site of callStack.

Since: base-4.9.0.0

getCallStack :: CallStack -> [([Char], SrcLoc)]

Extract a list of call-sites from the CallStack.

The list is ordered by most recent call.

Since: base-4.8.1.0

fromCallSiteList :: [([Char], SrcLoc)] -> CallStack

Convert a list of call-sites to a CallStack.

Since: base-4.9.0.0

prettySrcLoc :: SrcLoc -> String

Pretty print a SrcLoc.

Since: base-4.9.0.0

prettyCallStack :: CallStack -> String

Pretty-print a CallStack. This has a few differences from GHC.Stack.prettyCallStackLines. We omit the "CallStack (from GetCallStack)" header line for brevity. If there is only one entry (which is common, due to the manual nature of the HasCallStack constraint), shows the entry on one line. If there are multiple, then the following lines are indented.

withCallerCallStack :: HasCallStack => (CallStack -> b) -> b

prettyCallSite :: CallSite -> String

The same as the un-exported internal function in GHC.Exceptions (prettyCallStackLines) Prints like: doFoo, called at foo.hs:190:24 in main:Main

headCallSite :: CallStack -> Maybe CallSite

Get the most recent CallSite in a CallStack, if there is one.

withCurrentCallStack :: HasCallStack => (CallStack -> b) -> b

filterCallStack :: CallSiteFilter -> CallStack -> CallStack

Transform a CallStack by filtering each CallSite

overCallSites :: ([CallSite] -> [CallSite]) -> CallStack -> CallStack

Transform a CallStack by transforming its list of CallSite

popnCallStack :: Word -> CallStack -> CallStack

Pops n entries off a CallStack using popCallStack. Note that frozen callstacks are unaffected.

truncatedCallStack :: CallStack -> CallStack

CallStack comprising only the most recent CallSite

withNBackCallStack :: HasCallStack => Word -> (CallStack -> b) -> b