Agda-2.6.2.2: A dependently typed functional programming language and proof assistant
Safe HaskellNone
LanguageHaskell2010

Agda.Utils.CallStack

Synopsis

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>:2:1 in interactive:Ghci1

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

Instances details
IsList CallStack

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

Since: base-4.9.0.0

Instance details

Defined in GHC.Exts

Associated Types

type Item CallStack #

Show CallStack

Since: base-4.9.0.0

Instance details

Defined in GHC.Show

NFData CallStack

Since: deepseq-1.4.2.0

Instance details

Defined in Control.DeepSeq

Methods

rnf :: CallStack -> () #

Pretty CallStack Source # 
Instance details

Defined in Agda.Utils.CallStack.Pretty

EmbPrj CallStack Source # 
Instance details

Defined in Agda.TypeChecking.Serialise.Instances.Common

type Item CallStack 
Instance details

Defined in GHC.Exts

callStack :: HasCallStack => CallStack #

Return the current CallStack.

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

Since: base-4.9.0.0

prettySrcLoc :: SrcLoc -> String #

Pretty print a SrcLoc.

Since: base-4.9.0.0

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

Convert a list of call-sites to a 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

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

data SrcLoc #

A single location in the source code.

Since: base-4.8.1.0

Instances

Instances details
Eq SrcLoc

Since: base-4.9.0.0

Instance details

Defined in GHC.Stack.Types

Methods

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

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

Show SrcLoc

Since: base-4.9.0.0

Instance details

Defined in GHC.Show

NFData SrcLoc

Since: deepseq-1.4.2.0

Instance details

Defined in Control.DeepSeq

Methods

rnf :: SrcLoc -> () #

Pretty SrcLoc Source # 
Instance details

Defined in Agda.Utils.CallStack.Pretty

Pretty CallSite Source # 
Instance details

Defined in Agda.Utils.CallStack.Pretty

EmbPrj SrcLoc Source # 
Instance details

Defined in Agda.TypeChecking.Serialise.Instances.Common

type CallSiteFilter = CallSite -> Bool Source #

Type of a filter for CallSite

type CallSite = (SrcFun, SrcLoc) Source #

Type of an entry in a CallStack

type SrcLocCol = Int Source #

Type of a column of a SrcLoc

type SrcLocLine = Int Source #

Type of a line number of a SrcLoc

type SrcLocFile = String Source #

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

type SrcFun = String Source #

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

type SrcLocModule = String Source #

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

type SrcLocPackage = String Source #

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

prettyCallSite :: CallSite -> String Source #

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

prettyCallStack :: CallStack -> String Source #

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.

headCallSite :: CallStack -> Maybe CallSite Source #

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

truncatedCallStack :: CallStack -> CallStack Source #

CallStack comprising only the most recent CallSite

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

Transform a CallStack by transforming its list of CallSite

filterCallStack :: CallSiteFilter -> CallStack -> CallStack Source #

Transform a CallStack by filtering each CallSite

popnCallStack :: Word -> CallStack -> CallStack Source #

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