| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
Hedgehog.Internal.Source
Contents
Synopsis
- newtype LineNo = LineNo {}
- newtype ColumnNo = ColumnNo {
- unColumnNo :: Int
- data Span = Span {
- spanFile :: !FilePath
- spanStartLine :: !LineNo
- spanStartColumn :: !ColumnNo
- spanEndLine :: !LineNo
- spanEndColumn :: !ColumnNo
- getCaller :: CallStack -> Maybe Span
- data CallStack
- type HasCallStack = ?callStack :: CallStack
- callStack :: HasCallStack => CallStack
- withFrozenCallStack :: HasCallStack => (HasCallStack => a) -> a
Documentation
Instances
Constructors
| ColumnNo | |
Fields
| |
Instances
| Enum ColumnNo Source # | |
Defined in Hedgehog.Internal.Source | |
| Num ColumnNo Source # | |
| Integral ColumnNo Source # | |
Defined in Hedgehog.Internal.Source | |
| Real ColumnNo Source # | |
Defined in Hedgehog.Internal.Source Methods toRational :: ColumnNo -> Rational # | |
| Show ColumnNo Source # | |
| Eq ColumnNo Source # | |
| Ord ColumnNo Source # | |
Defined in Hedgehog.Internal.Source | |
Constructors
| Span | |
Fields
| |
Re-exports from GHC.Stack
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:
- If there is a
CallStackin scope -- i.e. the enclosing function has aHasCallStackconstraint -- GHC will append the new call-site to the existingCallStack. - If there is no
CallStackin scope -- e.g. in the GHCi session above -- and the enclosing definition does not have an explicit type signature, GHC will infer aHasCallStackconstraint for the enclosing definition (subject to the monomorphism restriction). - If there is no
CallStackin scope and the enclosing definition has an explicit type signature, GHC will solve theHasCallStackconstraint for the singletonCallStackcontaining 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
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
callStack :: HasCallStack => CallStack #
withFrozenCallStack :: HasCallStack => (HasCallStack => a) -> a #
Perform some computation without adding new entries to the CallStack.
Since: base-4.9.0.0