c2e4a69 · elk · git.iko.soy

git.iko.soy/elk

Pleasant messages when a pattern is missing

commitc2e4a69a902a2a9cddc7f3a475131f6fcb230a9d authorEvan Czaplicki <info@elm-lang.org> dateTue 18 Aug 2015, 18:36 (11 years ago) parentc61d87f

4 files changed+101−56

compare with master

unifiedsplit

elm-compiler.cabal+1 src/Nitpick/Pattern.hs+61 src/Nitpick/PatternMatches.hs+11−48 src/Reporting/Warning.hs+28−8

elm-compiler.cabal+1

@@ -79,6 +79,7 @@ Library

7979 Generate.JavaScript.Helpers,

8080 Generate.JavaScript.Port,

8181 Generate.JavaScript.Variable,

82+ Nitpick.Pattern,

8283 Nitpick.PatternMatches,

8384 Nitpick.TopLevelTypes,

8485 Optimize,

src/Nitpick/Pattern.hs+61

@@ -1,5 +1,6 @@

11module Nitpick.Pattern where

3+import qualified Data.List as List

34import qualified Data.Set as Set

56import qualified AST.Literal as L

@@ -8,3 +9,63 @@ import qualified AST.Variable as Var

89import qualified Reporting.Annotation as A

910

1011

12+data Pattern

13+ = Data Var.Canonical [Pattern]

14+ | Record [String]

15+ | Alias String Pattern

16+ | Var String

17+ | Anything

18+ | Literal L.Literal

19+ | AnythingBut (Set.Set L.Literal)

20+ deriving (Show, Eq)

21+

22+

23+fromCanonicalPattern :: P.CanonicalPattern -> Pattern

24+fromCanonicalPattern (A.A _ pattern) =

25+ case pattern of

26+ P.Data tag patterns ->

27+ Data tag (map fromCanonicalPattern patterns)

28+

29+ P.Record fields ->

30+ Record fields

31+

32+ P.Alias name pattern ->

33+ Alias name (fromCanonicalPattern pattern)

34+

35+ P.Var name ->

36+ Var name

37+

38+ P.Anything ->

39+ Anything

40+

41+ P.Literal literal ->

42+ Literal literal

43+

44+

45+-- TO STRING

46+

47+toString :: Pattern -> String

48+toString pattern =

49+ case pattern of

50+ Data tag args ->

51+ List.intercalate " " (Var.toString tag : map toString args)

52+

53+ Record fields ->

54+ "{ " ++ List.intercalate ", " fields ++ " }"

55+

56+ Alias alias realPattern ->

57+ toString realPattern ++ " as " ++ alias

58+

59+ Var name ->

60+ name

61+

62+ Anything ->

63+ "_"

64+

65+ Literal literal ->

66+ L.toString literal

67+

68+ AnythingBut literalSet ->

69+ List.intercalate " " ("<values besides:" : map L.toString (Set.toList literalSet))

70+

71+

src/Nitpick/PatternMatches.hs+11−48

@@ -10,11 +10,11 @@ import qualified Data.Set as Set

1010import qualified AST.Expression.General as E

1111import qualified AST.Expression.Canonical as Canonical

1212import qualified AST.Helpers as Help

13−import qualified AST.Literal as L

1413import qualified AST.Module as Module

15−import qualified AST.Pattern as P

14+import qualified AST.Pattern as Pattern

1615import qualified AST.Variable as Var

1716import Elm.Utils ((|>))

17+import Nitpick.Pattern (Pattern(..), fromCanonicalPattern)

1818import qualified Reporting.Annotation as A

1919import qualified Reporting.Region as Region

2020import qualified Reporting.Result as Result

@@ -35,42 +35,6 @@ patternMatches interfaces modul =

3535 (Module.program body)

3636

3737

38−-- PATTERN MATCH DATA STRUCTURE

39−

40−data Pattern

41− = Data Var.Canonical [Pattern]

42− | Record [String]

43− | Alias String Pattern

44− | Var String

45− | Anything

46− | Literal L.Literal

47− | AnythingBut (Set.Set L.Literal)

48− deriving (Show, Eq)

49−

50−

51−fromCanonicalPattern :: P.CanonicalPattern -> Pattern

52−fromCanonicalPattern (A.A _ pattern) =

53− case pattern of

54− P.Data ctor patterns ->

55− Data ctor (map fromCanonicalPattern patterns)

56−

57− P.Record fields ->

58− Record fields

59−

60− P.Alias name pattern ->

61− Alias name (fromCanonicalPattern pattern)

62−

63− P.Var name ->

64− Var name

65−

66− P.Anything ->

67− Anything

68−

69− P.Literal literal ->

70− Literal literal

71−

72−

73−

7438-- TAG DICT

7539

7640type TagDict =

@@ -116,8 +80,8 @@ toTagMapping adts =

11680 |> Map.fromList

11781

11882

119−lookupOtherCtors :: Var.Canonical -> TagDict -> [(Tag, Int)]

120−lookupOtherCtors (Var.Canonical home name) tagDict =

83+lookupOtherTags :: Var.Canonical -> TagDict -> [(Tag, Int)]

84+lookupOtherTags (Var.Canonical home name) tagDict =

12185 case Map.lookup name =<< Map.lookup home tagDict of

12286 Just otherTags ->

12387 otherTags

@@ -144,7 +108,7 @@ checkExpression tagDict (A.A region expression) =

144108 checkExpression tagDict

145109

146110 go2 a b =

147− F.traverse_ go [a,b]

111+ go a <* go b

148112

149113 goPattern =

150114 checkPatterns tagDict region

@@ -157,8 +121,7 @@ checkExpression tagDict (A.A region expression) =

157121 Result.ok ()

158122

159123 E.Range low high ->

160− go low

161− <* go high

124+ go2 low high

162125

163126 E.ExplicitList listExprs ->

164127 F.traverse_ go listExprs

@@ -232,7 +195,7 @@ checkExpression tagDict (A.A region expression) =

232195checkPatterns

233196 :: TagDict

234197 -> Region.Region

235− -> [P.CanonicalPattern]

198+ -> [Pattern.CanonicalPattern]

236199 -> Result.Result Warning.Warning e ()

237200checkPatterns tagDict region patterns =

238201 checkPatternsHelp tagDict region [Anything] patterns

@@ -242,7 +205,7 @@ checkPatternsHelp

242205 :: TagDict

243206 -> Region.Region

244207 -> [Pattern]

245− -> [P.CanonicalPattern]

208+ -> [Pattern.CanonicalPattern]

246209 -> Result.Result Warning.Warning e ()

247210checkPatternsHelp tagDict region unhandled patterns =

248211 case (unhandled, patterns) of

@@ -250,7 +213,7 @@ checkPatternsHelp tagDict region unhandled patterns =

250213 return ()

251214

252215 (_:_, []) ->

253− Result.warn region Warning.InexhaustivePatternMatch

216+ Result.warn region (Warning.InexhaustivePatternMatch unhandled)

254217

255218 (_, pattern@(A.A localRegion _) : remainingPatterns) ->

256219 do newUnhandled <- filterPatterns tagDict localRegion pattern unhandled

@@ -260,7 +223,7 @@ checkPatternsHelp tagDict region unhandled patterns =

260223filterPatterns

261224 :: TagDict

262225 -> Region.Region

263− -> P.CanonicalPattern

226+ -> Pattern.CanonicalPattern

264227 -> [Pattern]

265228 -> Result.Result Warning.Warning e [Pattern]

266229filterPatterns tagDict region pattern unhandled =

@@ -370,7 +333,7 @@ complementData :: TagDict -> Var.Canonical -> [Pattern] -> [Pattern]

370333complementData tagDict tag patterns =

371334 let

372335 otherTags =

373− lookupOtherCtors tag tagDict

336+ lookupOtherTags tag tagDict

374337

375338 tagComplements =

376339 Maybe.mapMaybe (tagToPattern tag) otherTags

src/Reporting/Warning.hs+28−8

@@ -9,6 +9,7 @@ import Text.PrettyPrint ((<+>))

1010import qualified AST.Module as Module

1111import qualified AST.Type as Type

12+import qualified Nitpick.Pattern as Pattern

1213import qualified Reporting.Annotation as A

1314import qualified Reporting.PrettyPrint as P

1415import qualified Reporting.Report as Report

@@ -19,7 +20,7 @@ import qualified Reporting.Report as Report

1920data Warning

2021 = UnusedImport Module.Name

2122 | MissingTypeAnnotation String Type.Canonical

22− | InexhaustivePatternMatch

23+ | InexhaustivePatternMatch [Pattern.Pattern]

2324 | RedundantPatternMatch

2425

2526

@@ -58,18 +59,24 @@ toReport dealiaser warning =

5859 4

5960 (P.pretty dealiaser False inferredType)

6061

61− InexhaustivePatternMatch ->

62+ InexhaustivePatternMatch unhandled ->

6263 Report.simple

6364 "missing pattern"

6465 "The following case expression does not handle all possible inputs."

65− ( "If none of the patterns match the given value, we have no choice but to crash!\n"

66+ ( "The following patterns are not being handled:\n"

67+ ++ viewPatternList unhandled

68+ ++ "\n\n"

69+ ++ "If we get values like this, we have no choice but to crash! Normally this means\n"

70+ ++ "you just added a new tag to a union type, but sometimes it can be because there\n"

71+ ++ "is something very odd about the data you are modeling. In those rare cases, you\n"

72+ ++ "probably want to either:\n"

6673 ++ "\n"

67− ++ "If you somehow know that this pattern can never happen, you want to:\n"

68− ++ "\n"

69− ++ " 1. Rethink the data structures you are using. Is there a way to model the\n"

70− ++ " values more precisely?\n"

74+ ++ " 1. Rethink the model. Maybe some cases are \"impossible\" but it is still\n"

75+ ++ " possible to construct such cases. Is there a way to model the values more\n"

76+ ++ " precisely such that \"impossible\" values truly are impossible?\n"

7177 ++ " 2. End the pattern match with a wildcard match that leads to an expression\n"

72− ++ " like: Debug.crash \"This should never happen, but I guess it can!\""

78+ ++ " like: Debug.crash \"If you are reading this, I have made a mistake!\"\n"

79+ ++ " Generally speaking, you do not want it to have to be this way."

7380 )

7481

7582 RedundantPatternMatch ->

@@ -93,3 +100,16 @@ toJson dealiaser filePath (A.A region warning) =

93100 , "type" .= ("warning" :: String)

94101 ]

95102 ++ additionalFields

103+

104+

105+-- PATTERN WARNINGS

106+

107+viewPatternList :: [Pattern.Pattern] -> String

108+viewPatternList unhandledPatterns =

109+ let

110+ (showPatterns, rest) =

111+ splitAt 4 unhandledPatterns

112+ in

113+ concatMap ((++) "\n ") $

114+ map Pattern.toString showPatterns

115+ ++ if null rest then [] else ["..."]