2 {-# OPTIONS_GHC -fno-implicit-prelude #-}
3 -----------------------------------------------------------------------------
6 -- Copyright : (c) The University of Glasgow, 1994-2002
7 -- License : see libraries/base/LICENSE
9 -- Maintainer : cvs-ghc@haskell.org
10 -- Stability : internal
11 -- Portability : non-portable (GHC extensions)
13 -- The "GHC.Err" module defines the code for the wired-in error functions,
14 -- which have a special type in the compiler (with \"open tyvars\").
16 -- We cannot define these functions in a module where they might be used
17 -- (e.g., "GHC.Base"), because the magical wired-in type will get confused
18 -- with what the typechecker figures out.
20 -----------------------------------------------------------------------------
25 , noMethodBindingError
26 , nonExhaustiveGuardsError
30 , runtimeError -- :: Addr# -> a -- Addr# points to UTF8 encoded C string
33 , divZeroError -- :: a
35 , error -- :: String -> a
36 , assertError -- :: String -> Bool -> a -> a
43 import GHC.List ( span )
48 %*********************************************************
50 \subsection{Error-ish functions}
52 %*********************************************************
55 -- | 'error' stops execution and displays an error message.
57 error s = throw (ErrorCall s)
59 -- | A special case of 'error'.
60 -- It is expected that compilers will recognize this and insert error
61 -- messages which are more appropriate to the context in which 'undefined'
65 undefined = error "Prelude.undefined"
68 %*********************************************************
70 \subsection{Compiler generated errors + local utils}
72 %*********************************************************
74 Used for compiler-generated error message;
75 encoding saves bytes of string junk.
80 absentErr = error "Oops! The program has entered an `absent' argument!\n"
84 recSelError, recConError, irrefutPatError, runtimeError,
85 nonExhaustiveGuardsError, patError, noMethodBindingError
86 :: Addr# -> a -- All take a UTF8-encoded C string
88 recSelError s = throw (RecSelError (unpackCStringUtf8# s)) -- No location info unfortunately
89 runtimeError s = error (unpackCStringUtf8# s) -- No location info unfortunately
91 nonExhaustiveGuardsError s = throw (PatternMatchFail (untangle s "Non-exhaustive guards in"))
92 irrefutPatError s = throw (PatternMatchFail (untangle s "Irrefutable pattern failed for pattern"))
93 recConError s = throw (RecConError (untangle s "Missing field in record construction"))
94 noMethodBindingError s = throw (NoMethodError (untangle s "No instance nor default method for class operation"))
95 patError s = throw (PatternMatchFail (untangle s "Non-exhaustive patterns in"))
97 assertError :: Addr# -> Bool -> a -> a
98 assertError str pred v
100 | otherwise = throw (AssertionFailed (untangle str "Assertion failed"))
104 (untangle coded message) expects "coded" to be of the form
110 location message details
113 untangle :: Addr# -> String -> String
114 untangle coded message
121 coded_str = unpackCStringUtf8# coded
124 = case (span not_bar coded_str) of { (loc, rest) ->
126 ('|':det) -> (loc, ' ' : det)
132 Divide by zero. We put it here because it is needed relatively early
133 in the libraries before the Exception type has been defined yet.
136 {-# NOINLINE divZeroError #-}
138 divZeroError = throw (ArithException DivideByZero)