Fix #15953 by consistently using dumpIfSet_dyn to print debug output

Summary:
In some modules we directly dump the debugging output to STDOUT
via 'putLogMsg', 'printInfoForUser' etc. However, if `-ddump-to-file`
is enabled, that output should be written to a file. Easily fixed.

Certain tests (T3017, Roles3, T12763 etc.) expect part of the
output generated by `-ddump-types` to be in 'PprUser' style. However,
generally we want all other debugging output to use 'PprDump'
style. `traceTcRn` and `traceTcRnForUser` help us accomplish this.

This patch also documents some missing flags in the users guide.

Reviewers: RyanGlScott, bgamari, hvr

Reviewed By: RyanGlScott

Subscribers: rwbarton, carter

GHC Trac Issues: #15953

Differential Revision: https://phabricator.haskell.org/D5382

1 files changed, 3 insertions, 3 deletions

diff --git a/compiler/main/InteractiveEval.hs b/compiler/main/InteractiveEval.hs
index 3d9dc18970..cceec31fec 100644
--- a/compiler/main/InteractiveEval.hs
+++ b/compiler/main/InteractiveEval.hs
@@ -576,9 +576,9 @@ rttiEnvironment hsc_env@HscEnv{hsc_IC=ic} = do
                                            ++ "improvement for a type")) hsc_env
                Just subst -> do
                  let dflags = hsc_dflags hsc_env
-                 when (dopt Opt_D_dump_rtti dflags) $
-                      printInfoForUser dflags alwaysQualify $
-                      fsep [text "RTTI Improvement for", ppr id, equals, ppr subst]
+                 dumpIfSet_dyn dflags Opt_D_dump_rtti "RTTI"
+                   (fsep [text "RTTI Improvement for", ppr id, equals,
+                          ppr subst])
 
                  let ic' = substInteractiveContext ic subst
                  return hsc_env{hsc_IC=ic'}