diff options
Diffstat (limited to 'compiler/GHC/Rename/Env.hs')
| -rw-r--r-- | compiler/GHC/Rename/Env.hs | 35 |
1 files changed, 31 insertions, 4 deletions
diff --git a/compiler/GHC/Rename/Env.hs b/compiler/GHC/Rename/Env.hs index e9733a8bfc..0c0e944d64 100644 --- a/compiler/GHC/Rename/Env.hs +++ b/compiler/GHC/Rename/Env.hs @@ -1097,6 +1097,9 @@ lookup_demoted rdr_name | otherwise = star_is_type_hints ; unboundNameX looking_for rdr_name suggestion } } + | Just demoted_rdr_name <- demoteRdrNameTv rdr_name, + isQual rdr_name + = report_qualified_term_in_types rdr_name demoted_rdr_name | otherwise = reportUnboundName' (lf_which looking_for) rdr_name @@ -1104,6 +1107,18 @@ lookup_demoted rdr_name where looking_for = LF WL_Constructor WL_Anywhere +-- Report a qualified variable name in a type signature: +-- badSig :: Prelude.head +-- ^^^^^^^^^^^ +report_qualified_term_in_types :: RdrName -> RdrName -> RnM Name +report_qualified_term_in_types rdr_name demoted_rdr_name = + do { mName <- lookupGlobalOccRn_maybe demoted_rdr_name + ; case mName of + (Just _) -> termNameInType looking_for rdr_name demoted_rdr_name [] + Nothing -> unboundTermNameInTypes looking_for rdr_name demoted_rdr_name } + where + looking_for = LF WL_Constructor WL_Global + -- If the given RdrName can be promoted to the type level and its promoted variant is in scope, -- lookup_promoted returns the corresponding type-level Name. -- Otherwise, the function returns Nothing. @@ -1152,14 +1167,26 @@ its namespace to DataName and do a second lookup. The final result (after the renamer) will be: HsTyVar ("Zero", DataName) -Another case of demotion happens when the compiler needs to check +Another case of demotion happens when the user tries to +use a qualified term at the type level: + + f :: Prelude.id -> Int + +This signature passes the parser to be caught by the renamer. +It allows the compiler to create more informative error messages. + +'Prelude.id' in the type signature is parsed as + HsTyVar ("id", TvName) + +To separate the case of a typo from the case of an +intentional attempt to use an imported term's name the compiler demotes +the namespace to VarName (using 'demoteTvNameSpace') and does a lookup. + +The same type of demotion happens when the compiler needs to check if a name of a type variable has already been used for a term that is in scope. We need to do it to check if a user should change the name to make his code compatible with the RequiredTypeArguments extension. -This type of demotion is made via demoteTvNameSpace. - - Note [Promotion] ~~~~~~~~~~~~~~~ When the user mentions a type constructor or a type variable in a |