75ccf81 · elk · git.iko.soy

git.iko.soy/elk

Give nicer errors for bad function defs and for duplicate variables in patterns

Fix #868

commit75ccf81a6d8f5c26103666885900d9d47c6d1dea authorEvan Czaplicki <info@elm-lang.org> dateMon 28 Sep 2015, 16:03 (11 years ago) parent5473c62

3 files changed+67−30

compare with master

unifiedsplit

src/Parse/Expression.hs+6−24 src/Reporting/Error/Syntax.hs+22 src/Validate.hs+39−6

src/Parse/Expression.hs+6−24

@@ -296,7 +296,7 @@ definition :: IParser Source.Def

296296definition =

297297 addLocation $

298298 withPos $

299− do (name:args) <- defStart

299+ do (name, args) <- defStart

300300 padded equals

301301 body <- expr

302302 return . Source.Definition name $ makeFunction args body

@@ -307,27 +307,9 @@ makeFunction args body@(A.A ann _) =

307307 foldr (\arg body' -> A.A ann $ E.Lambda arg body') body args

308308

309309

310−defStart :: IParser [P.RawPattern]

310+defStart :: IParser (P.RawPattern, [P.RawPattern])

311311defStart =

312− choice

313− [ do pattern <- try Pattern.term

314− infics pattern <|> func pattern

315− , do opPattern <- addLocation (P.Var <$> parens symOp)

316− func opPattern

317− ]

318− <?> "the definition of a variable (x = ...)"

319− where

320− func pattern =

321− case pattern of

322− A.A _ (P.Var _) ->

323− (pattern:) <$> spacePrefix Pattern.term

324−

325− _ ->

326− return [pattern]

327−

328− infics p1 =

329− do (start, o:p, end) <- try (whitespace >> located anyOp)

330− p2 <- (whitespace >> Pattern.term)

331− let opName =

332− if o == '`' then takeWhile (/='`') p else o:p

333− return [ A.at start end (P.Var opName), p1, p2 ]

312+ expecting "the definition of a value (x = ...)" $

313+ do starter <- try Pattern.term <|> addLocation (P.Var <$> parens symOp)

314+ args <- spacePrefix Pattern.term

315+ return (starter, args)

src/Reporting/Error/Syntax.hs+22

@@ -15,6 +15,8 @@ import qualified Reporting.Report as Report

1515

1616data Error

1717 = Parse [Parsec.Message]

18+ | BadFunctionName Int

19+ | BadPattern String

1820 | InfixDuplicate String

1921 | TypeWithoutDefinition String

2022 | PortWithoutAnnotation String

@@ -34,6 +36,26 @@ toReport dealiaser err =

3436 Parse messages ->

3537 parseErrorReport messages

3638

39+ BadFunctionName arity ->

40+ Report.simple

41+ "BAD FUNCTION DEFINITION"

42+ "Complex patterns cannot be used as function names."

43+ ( "This function definition has " ++ show arity ++ " arguments, but instead of a normal name like\n"

44+ ++ "`add` or `reverse` it has a pattern. There is no way to \"deconstruct\" a\n"

45+ ++ "function with pattern matching, so this needs to be changed to a normal name."

46+ )

47+

48+ BadPattern name ->

49+ Report.simple

50+ "BAD PATTERN"

51+ ("The free variable `" ++ name ++ "` appears more than once in this pattern.")

52+ ( "Rename the variables so there are no duplicates.\n\n"

53+ ++ "In Elm, pattern matching works by binding these free variables to subsections\n"

54+ ++ "of the matching value. It does not make sense to have the same name for two\n"

55+ ++ "different subsections though! When you say `" ++ name ++ "` in some code, there\n"

56+ ++ "is no way for me to know which subsection you mean!"

57+ )

58+

3759 InfixDuplicate opName ->

3860 Report.simple

3961 "INFIX OVERLAP"

src/Validate.hs+39−6

@@ -7,7 +7,7 @@ import qualified Data.Set as Set

77import qualified Data.Foldable as F

88import qualified Data.Traversable as T

10−import AST.Expression.General

10+import AST.Expression.General as Expr

1111import qualified AST.Expression.Source as Source

1212import qualified AST.Expression.Valid as Valid

1313import qualified AST.Declaration as D

@@ -92,8 +92,9 @@ defHelp comment (A.A region def) decls =

9292 in

9393 case def of

9494 Source.Definition pat expr ->

95− do expr' <- Validate.expression expr

95+ do expr' <- expression expr

9696 let def' = Valid.Definition pat expr' Nothing

97+ checkDefinition def'

9798 addRest def' decls

9899

99100 Source.TypeAnnotation name tipe ->

@@ -101,8 +102,9 @@ defHelp comment (A.A region def) decls =

101102 D.Decl (A.A _ (D.Definition (A.A _

102103 (Source.Definition pat@(A.A _ (Pattern.Var name')) expr)))) : rest

103104 | name == name' ->

104− do expr' <- Validate.expression expr

105+ do expr' <- expression expr

105106 let def' = Valid.Definition pat expr' (Just tipe)

107+ checkDefinition def'

106108 addRest def' rest

107109

108110 _ ->

@@ -130,7 +132,7 @@ portHelp comment region port decls =

130132 case decls of

131133 D.Decl (A.A _ (D.Port (D.PortDefinition name' expr))) : rest

132134 | name == name' ->

133− do expr' <- Validate.expression expr

135+ do expr' <- expression expr

134136 let port' = D.Out name expr' tipe

135137 addRest port' rest

136138

@@ -157,6 +159,7 @@ definitionsHelp sourceDefs =

157159 A.A _ (Source.Definition pat expr) : rest ->

158160 do expr' <- expression expr

159161 let def = Valid.Definition pat expr' Nothing

162+ checkDefinition def

160163 (:) def <$> definitionsHelp rest

161164

162165 A.A region (Source.TypeAnnotation name tipe) : rest ->

@@ -165,12 +168,32 @@ definitionsHelp sourceDefs =

165168 | name == name' ->

166169 do expr' <- expression expr

167170 let def = Valid.Definition pat expr' (Just tipe)

171+ checkDefinition def

168172 (:) def <$> definitionsHelp rest'

169173

170174 _ ->

171175 Result.throw region (Error.TypeWithoutDefinition name)

172176

173177

178+checkDefinition :: Valid.Def -> Result.Result wrn Error.Error ()

179+checkDefinition (Valid.Definition pattern body _) =

180+ case fst (Expr.collectLambdas body) of

181+ [] ->

182+ return ()

183+

184+ args ->

185+ case pattern of

186+ A.A _ (Pattern.Var _) ->

187+ return ()

188+

189+ _ ->

190+ let

191+ (A.A start _) = pattern

192+ (A.A end _) = last args

193+ in

194+ Result.throw (R.merge start end) (Error.BadFunctionName (length args))

195+

196+

174197-- VALIDATE EXPRESSIONS

175198

176199expression :: Source.Expr -> Result.Result wrn Error.Error Valid.Expr

@@ -181,7 +204,9 @@ expression (A.A ann sourceExpression) =

181204 return (Var x)

182205

183206 Lambda pattern body ->

184− Lambda pattern <$> expression body

207+ Lambda

208+ <$> validatePattern pattern

209+ <*> expression body

185210

186211 Binop op leftExpr rightExpr ->

187212 Binop op

@@ -191,7 +216,7 @@ expression (A.A ann sourceExpression) =

191216 Case e branches ->

192217 Case

193218 <$> expression e

194− <*> T.traverse second branches

219+ <*> T.traverse (\(p,b) -> (,) <$> validatePattern p <*> expression b) branches

195220

196221 Data name args ->

197222 Data name <$> T.traverse expression args

@@ -267,6 +292,14 @@ both (expr1, expr2) =

267292 (,) <$> expression expr1 <*> expression expr2

268293

269294

295+-- VALIDATE PATTERNS

296+

297+validatePattern :: Pattern.RawPattern -> Result.Result wrn Error.Error Pattern.RawPattern

298+validatePattern pattern =

299+ do detectDuplicates Error.BadPattern (Pattern.boundVars pattern)

300+ return pattern

301+

302+

270303-- DETECT DUPLICATES

271304

272305detectDuplicates