Hi,
In some cases, the line number in an error message does not point to the
place in the source code where the error actually comes from.
For example, when you compile the following program in the StdEnv
environment.
module compileErrorList
import StdEnv
test =
[ 10
, 20
, 30 + "foo"
]
Start = Start
You get this error message.
Type error [compileErrorList.icl,3,test]:"argument 1 of +" cannot unify types:
String
Int
The error message points to line 3, while the error comes from line 6.
The rest of the error message identifies the argument of the plus
operator as the culprit. It seems that the compiler in principle has
enough information to pinpoint the origin of the error more precisely.
Another example is the following program, which must be compiled in the
iTasks environment.
module compileErrorMonad
import Control.Monad
import System.IO
test =
putStrLn "hello" >>|
putStrLn "world" >>|
putStrLn 42
Start = Start
The error message is:
Type error [compileErrorMonad.icl,4,test]:"argument 1 of putStrLn" cannot
unify demanded type with offered type:
String
Int
The compiler seems to know that the argument of the third putStrLn is the
problem, but the source location of the error message points to line 4.
Is it possible to let the compiler output source locations that relate
more closely to the origin of errors?
Best regards,
Markus
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