Question

Sometimes I get annoying pattern matching and indent warnings when compiling F#. Is there a way to disable warnings? I’m pretty OCD over warnings.

Answer 1

In case you forget, you can type

let rec x = lazy(x.Value)

and get the warning

This and other recursive references to
the object(s) being defined will be
checked for initialization-soundness
at runtime through the use of a
delayed reference. This is because you
are defining one or more recursive
objects, rather than recursive
functions. This warning may be
suppressed by using ‘#nowarn “40”‘ or
‘–nowarn:40’.

which shows that you can use either the compiler flag --nowarn on the command-line, or use the hash-directive #nowarn in your code. The warning number for each warning will be part of the build output (the Visual Studio error list does not display the numbers, so if in VS, build and then inspect the build output). Also, if inside VS, you can go to the project properties page, “Build” tab, and use the “warning level” selector and “suppress warnings” field (a semicolon-delimited list of numbers) to control which warnings are diplayed via the VS UI.

(BTW, I believe #nowarn only turns off the warning in the current file, whereas --nowarn turns it off for the entire project being compiled.)