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parser-typechecker/src/Unison/Syntax/TermPrinter.hs

@@ -2119,8 +2119,9 @@ nameEndsWith ppe suffix r = case PrettyPrintEnv.termName ppe (Referent.Ref r) of
 -- Algorithm is the following:
 --   1. Form the set of all local variables used anywhere in the term
 --   2. When picking a name for a term, see if it is contained in this set.
---      If yes, use the qualified name for the term (which PPE conveniently provides)
---      If no, use the suffixed name for the term
+--      If yes: use a minimally qualified name which is longer than the suffixed name,
+--              but doesn't conflict with any local vars.
+--      If no: use the suffixed name for the term
 --
 -- The algorithm does the same for type references in signatures.
 --
@@ -2150,10 +2151,14 @@ avoidShadowing tm (PrettyPrintEnv terms types) =
               minimallySuffixed :: HQ'.HashQualified Name
               minimallySuffixed =
                 revFQNSegments
+                  -- Get all suffixes (it's inits instead of tails because name segments are in reverse order)
                   & NEL.inits
+                  -- Drop the empty 'init'
                   & NEL.tail
-                  & mapMaybe (fmap Name.fromReverseSegments . NEL.nonEmpty)
+                  & mapMaybe (fmap Name.fromReverseSegments . NEL.nonEmpty) -- Convert back into names
+                  -- Drop the suffixes that we know are shorter than the suffixified name
                   & List.drop (Name.countSegments suffixedName)
+                  -- Drop the suffixes that are equal to local variables
                   & filter ((\n -> n `Set.notMember` used))
                   & listToMaybe
                   & maybe fullName HQ'.NameOnly