99a44a0 · elk · git.iko.soy

git.iko.soy/elk

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Turn incomplete pattern matches into a static error

99a44a0Evan Czaplicki11 years ago

elm-compiler.cabal+1

compare with master

unifiedsplit

@@ -103,6 +103,7 @@ Library

103 Reporting.Error.Canonicalize,

104 Reporting.Error.Docs,

105 Reporting.Error.Helpers,

106+ Reporting.Error.Pattern,

106 Reporting.Error.Syntax,

107 Reporting.Error.Syntax,

107 Reporting.Error.Type,

108 Reporting.Error.Type,

108 Reporting.PrettyPrint,

109 Reporting.PrettyPrint,

src/Compile.hs+2−1

@@ -45,7 +45,8 @@ compile packageName isRoot canonicalImports interfaces source =

45 Result.mapError Error.Type $

46 Nitpick.topLevelTypes types (Module.body validModule)

48+ Result.mapError Error.Pattern $

48− Nitpick.patternMatches interfaces canonicalModule

49+ Nitpick.patternMatches interfaces canonicalModule

50 -- Add the real list of types

51 -- Add the real list of types

51 let body = (Module.body canonicalModule) { Module.types = types }

52 let body = (Module.body canonicalModule) { Module.types = types }

src/Nitpick/PatternMatches.hs+9−9

@@ -17,15 +17,15 @@ import qualified AST.Variable as Var

17import Elm.Utils ((|>))

18import Nitpick.Pattern (Pattern(..), fromCanonicalPattern)

19import qualified Reporting.Annotation as A

20+import qualified Reporting.Error.Pattern as Error

20import qualified Reporting.Region as Region

21import qualified Reporting.Region as Region

21import qualified Reporting.Result as Result

22import qualified Reporting.Result as Result

22−import qualified Reporting.Warning as Warning

25patternMatches

26 :: Module.Interfaces

27 -> Module.CanonicalModule

28− -> Result.Result Warning.Warning e ()

28+ -> Result.Result w Error.Error ()

29patternMatches interfaces modul =

30 let

31 name = Module.name modul

@@ -102,7 +102,7 @@ lookupOtherTags (Var.Canonical home name) tagDict =

102checkExpression

103 :: TagDict

104 -> Canonical.Expr

105− -> Result.Result Warning.Warning e ()

105+ -> Result.Result w Error.Error ()

106checkExpression tagDict (A.A region expression) =

107 let

108 go =

@@ -188,7 +188,7 @@ checkPatterns

188 :: TagDict

189 -> Region.Region

190 -> [Pattern.CanonicalPattern]

191− -> Result.Result Warning.Warning e ()

191+ -> Result.Result w Error.Error ()

192checkPatterns tagDict region patterns =

193 checkPatternsHelp tagDict region [Anything] patterns

194

@@ -198,14 +198,14 @@ checkPatternsHelp

198 -> Region.Region

199 -> [Pattern]

200 -> [Pattern.CanonicalPattern]

201− -> Result.Result Warning.Warning e ()

201+ -> Result.Result w Error.Error ()

202checkPatternsHelp tagDict region unhandled patterns =

203 case (unhandled, patterns) of

204 ([], []) ->

205 return ()

206

207 (_:_, []) ->

208− Result.warn region (Warning.InexhaustivePatternMatch unhandled)

208+ Result.throw region (Error.Incomplete unhandled)

209

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

211 do newUnhandled <- filterPatterns tagDict localRegion pattern unhandled

@@ -217,7 +217,7 @@ filterPatterns

217 -> Region.Region

218 -> Pattern.CanonicalPattern

219 -> [Pattern]

220− -> Result.Result Warning.Warning e [Pattern]

220+ -> Result.Result w Error.Error [Pattern]

221filterPatterns tagDict region pattern unhandled =

222 let

223 nitPattern =

@@ -227,8 +227,8 @@ filterPatterns tagDict region pattern unhandled =

227 intersection pat nitPattern == Nothing

228 in

229 if all noIntersection unhandled then

230− do Result.warn region Warning.RedundantPatternMatch

230+ Result.throw region Error.Redundant

231− return unhandled

231+

232 else

233 do let complementPatterns = complement tagDict nitPattern

234 return $

src/Reporting/Error.hs+8

@@ -9,6 +9,7 @@ import Prelude hiding (print)

9import qualified Reporting.Annotation as A

10import qualified Reporting.Error.Canonicalize as Canonicalize

11import qualified Reporting.Error.Docs as Docs

12+import qualified Reporting.Error.Pattern as Pattern

12import qualified Reporting.Error.Syntax as Syntax

13import qualified Reporting.Error.Syntax as Syntax

13import qualified Reporting.Error.Type as Type

14import qualified Reporting.Error.Type as Type

14import qualified Reporting.PrettyPrint as P

15import qualified Reporting.PrettyPrint as P

@@ -21,6 +22,7 @@ data Error

21 = Syntax Syntax.Error

22 = Syntax Syntax.Error

22 | Canonicalize Canonicalize.Error

23 | Canonicalize Canonicalize.Error

23 | Type Type.Error

24 | Type Type.Error

25+ | Pattern Pattern.Error

24 | Docs Docs.Error

26 | Docs Docs.Error

@@ -38,6 +40,9 @@ toReport dealiaser err =

38 Type typeError ->

40 Type typeError ->

39 Type.toReport dealiaser typeError

41 Type.toReport dealiaser typeError

43+ Pattern patternError ->

44+ Pattern.toReport dealiaser patternError

45+

41 Docs docsError ->

46 Docs docsError ->

42 Docs.toReport docsError

47 Docs.toReport docsError

@@ -76,6 +81,9 @@ toJson dealiaser filePath (A.A region err) =

76 Type typeError ->

81 Type typeError ->

77 Report.toJson [] (Type.toReport dealiaser typeError)

82 Report.toJson [] (Type.toReport dealiaser typeError)

84+ Pattern patternError ->

85+ Report.toJson [] (Pattern.toReport dealiaser patternError)

86+

79 Docs docsError ->

87 Docs docsError ->

80 Report.toJson [] (Docs.toReport docsError)

88 Report.toJson [] (Docs.toReport docsError)

81 in

89 in

src/Reporting/Error/Pattern.hsnew file+69

@@ -0,0 +1,69 @@

1+{-# OPTIONS_GHC -Wall #-}

2+module Reporting.Error.Pattern where

4+import qualified Data.Char as Char

5+import Text.PrettyPrint ((<+>))

6+import qualified Text.PrettyPrint as P

8+import qualified AST.Helpers as Help

9+import qualified AST.Type as Type

10+import qualified AST.Variable as Var

11+import qualified Nitpick.Pattern as Pattern

12+import qualified Reporting.PrettyPrint as P

13+import qualified Reporting.Region as Region

14+import qualified Reporting.Report as Report

15+

16+

17+data Error

18+ = Incomplete [Pattern.Pattern]

19+ | Redundant

20+

21+

22+-- TO REPORT

23+

24+toReport :: P.Dealiaser -> Error -> Report.Report

25+toReport dealiaser err =

26+ case err of

27+ Incomplete unhandled ->

28+ Report.simple

29+ "MISSING PATTERN"

30+ "The following `case` does not handle all possible inputs."

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

32+ ++ viewPatternList unhandled

33+ ++ "\n\n"

34+ ++ "Did you add a new tag to a union type? Add how it should be handled here and"

35+ ++ "you will be all set!"

36+ ++ ""

37+ ++ "If you want to go quick and implement this later, you can end the pattern with:"

38+ ++ ""

39+ ++ " _ ->"

40+ ++ " Debug.crash \"TODO\""

41+ ++ ""

42+ ++ "When I see cases that end with this pattern, I augment the runtime error with"

43+ ++ "the module name, the relevant line numbers, and the value led down that branch."

44+ ++ ""

45+ ++ "That said, you almost never want this in production code. If you think there"

46+ ++ "are certain cases that are impossible in practice, consider refining how you"

47+ ++ "model the data. If it can never happen in practice, you can probably define a"

48+ ++ "union type such that the \"impossible\" cannot even be constructed in the"

49+ ++ "first place. That is how you make something \"impossible\" truly impossible."

50+ ++ ""

51+ ++ "I won't say \"I told you so\" in the runtime error, but I'll be thinking it ;)"

52+ )

53+

54+ Redundant ->

55+ Report.simple

56+ "REDUNDANT PATTERN"

57+ "The following pattern is redundant."

58+ "Any value with this shape will be handled by a previous pattern."

59+

60+

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

62+viewPatternList unhandledPatterns =

63+ let

64+ (showPatterns, rest) =

65+ splitAt 4 unhandledPatterns

66+ in

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

68+ map Pattern.toString showPatterns

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

src/Reporting/Warning.hs−42

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

10import qualified AST.Module.Name as ModuleName

11import qualified AST.Type as Type

12−import qualified Nitpick.Pattern as Pattern

13import qualified Reporting.Annotation as A

12import qualified Reporting.Annotation as A

14import qualified Reporting.PrettyPrint as P

13import qualified Reporting.PrettyPrint as P

15import qualified Reporting.Report as Report

14import qualified Reporting.Report as Report

@@ -20,8 +19,6 @@ import qualified Reporting.Report as Report

20data Warning

19data Warning

21 = UnusedImport ModuleName.Raw

20 = UnusedImport ModuleName.Raw

22 | MissingTypeAnnotation String Type.Canonical

21 | MissingTypeAnnotation String Type.Canonical

23− | InexhaustivePatternMatch [Pattern.Pattern]

24− | RedundantPatternMatch

27-- TO STRING

24-- TO STRING

@@ -59,32 +56,6 @@ toReport dealiaser warning =

59 4

56 4

60 (P.pretty dealiaser False inferredType)

57 (P.pretty dealiaser False inferredType)

62− InexhaustivePatternMatch unhandled ->

63− Report.simple

64− "missing pattern"

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

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"

73− ++ "\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"

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

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."

80− )

81−

82− RedundantPatternMatch ->

83− Report.simple

84− "redundant pattern"

85− "The following pattern is redundant."

86− "Any value with this shape will be handled by a previous pattern."

87−

89-- TO JSON

60-- TO JSON

@@ -100,16 +71,3 @@ toJson dealiaser filePath (A.A region warning) =

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

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

101 ]

72 ]

102 ++ additionalFields

73 ++ 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 ["..."]