WildcardsInPatternAndExprSig.hs:4:18: error:
    Found type wildcard ‘_a’ standing for ‘t’
    Where: ‘t’ is a rigid type variable bound by
               the inferred type of bar :: Maybe [t] -> t -> [t]
               at WildcardsInPatternAndExprSig.hs:4:1
    To use the inferred type, enable PartialTypeSignatures
    Relevant bindings include
      bar :: Maybe [t] -> t -> [t]
        (bound at WildcardsInPatternAndExprSig.hs:4:1)
    In a pattern type signature: _a
    In the pattern: x :: _a
    In the pattern: [x :: _a]

WildcardsInPatternAndExprSig.hs:4:25: error:
    Found type wildcard ‘_’ standing for ‘[t]’
    Where: ‘t’ is a rigid type variable bound by
               the inferred type of bar :: Maybe [t] -> t -> [t]
               at WildcardsInPatternAndExprSig.hs:4:1
    To use the inferred type, enable PartialTypeSignatures
    Relevant bindings include
      bar :: Maybe [t] -> t -> [t]
        (bound at WildcardsInPatternAndExprSig.hs:4:1)
    In a pattern type signature: _
    In the pattern: [x :: _a] :: _
    In the pattern: Just ([x :: _a] :: _)

WildcardsInPatternAndExprSig.hs:4:38: error:
    Found type wildcard ‘_b’ standing for ‘t’
    Where: ‘t’ is a rigid type variable bound by
               the inferred type of bar :: Maybe [t] -> t -> [t]
               at WildcardsInPatternAndExprSig.hs:4:1
    To use the inferred type, enable PartialTypeSignatures
    Relevant bindings include
      bar :: Maybe [t] -> t -> [t]
        (bound at WildcardsInPatternAndExprSig.hs:4:1)
    In a pattern type signature: Maybe [_b]
    In the pattern: Just ([x :: _a] :: _) :: Maybe [_b]
    In an equation for ‘bar’:
        bar (Just ([x :: _a] :: _) :: Maybe [_b]) (z :: _c)
          = [x, z] :: [_d]

WildcardsInPatternAndExprSig.hs:4:49: error:
    Found type wildcard ‘_c’ standing for ‘t’
    Where: ‘t’ is a rigid type variable bound by
               the inferred type of bar :: Maybe [t] -> t -> [t]
               at WildcardsInPatternAndExprSig.hs:4:1
    To use the inferred type, enable PartialTypeSignatures
    Relevant bindings include
      x :: t (bound at WildcardsInPatternAndExprSig.hs:4:13)
      bar :: Maybe [t] -> t -> [t]
        (bound at WildcardsInPatternAndExprSig.hs:4:1)
    In a pattern type signature: _c
    In the pattern: z :: _c
    In an equation for ‘bar’:
        bar (Just ([x :: _a] :: _) :: Maybe [_b]) (z :: _c)
          = [x, z] :: [_d]

WildcardsInPatternAndExprSig.hs:4:66: error:
    Found type wildcard ‘_d’ standing for ‘t’
    Where: ‘t’ is a rigid type variable bound by
               the inferred type of bar :: Maybe [t] -> t -> [t]
               at WildcardsInPatternAndExprSig.hs:4:1
    To use the inferred type, enable PartialTypeSignatures
    Relevant bindings include
      z :: t (bound at WildcardsInPatternAndExprSig.hs:4:44)
      x :: t (bound at WildcardsInPatternAndExprSig.hs:4:13)
      bar :: Maybe [t] -> t -> [t]
        (bound at WildcardsInPatternAndExprSig.hs:4:1)
    In an expression type signature: [_d]
    In the expression: [x, z] :: [_d]
    In an equation for ‘bar’:
        bar (Just ([x :: _a] :: _) :: Maybe [_b]) (z :: _c)
          = [x, z] :: [_d]