0769e58 · elk · git.iko.soy

git.iko.soy/elk

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Improve type error messages for case-expressions

0769e58Evan Czaplicki11 years ago

src/Reporting/Error/Type.hs+8−1

compare with master

unifiedsplit

@@ -26,6 +26,7 @@ data Hint

26 = None

27 | Custom String

28 | CaseBranch Int Region.Region

29+ | Case

29 | IfBranches

30 | IfBranches

30 | MultiIfBranch Int Region.Region

31 | MultiIfBranch Int Region.Region

31 | If

32 | If

@@ -93,6 +94,12 @@ hintToString hint =

93 ++ "branch returns the same type of value."

94 ++ "branch returns the same type of value."

94 )

95 )

97+ Case ->

98+ ( Nothing

99+ , "All the branches of this case-expression are consistent, but the overall\n"

100+ ++ "type does not match how it is used elsewhere."

101+ )

102+

96 IfBranches ->

103 IfBranches ->

97 ( Nothing

104 ( Nothing

98 , "The branches of this if-expression return different types of values.\n"

105 , "The branches of this if-expression return different types of values.\n"

@@ -108,6 +115,6 @@ hintToString hint =

108

115

109 If ->

116 If ->

110 ( Nothing

117 ( Nothing

111− , "All the branches of this if-expression are consistent, but the overall return\n"

118+ , "All the branches of this if-expression are consistent, but the overall\n"

112 ++ "type does not match how it is used elsewhere."

119 ++ "type does not match how it is used elsewhere."

113 )

120 )

src/Type/Constrain/Expression.hs+19−11

@@ -254,28 +254,36 @@ constrainCase env region expr branches tipe =

254

255 exprCon <- constrain env expr (varN exprVar)

256

257− (branchVars, regions, branchExprCons) <-

257+ (branchInfo, branchExprCons) <-

258− unzip3 <$> mapM (branch (varN exprVar)) branches

258+ unzip <$> mapM (branch (varN exprVar)) branches

259−

260− let branchCons =

261− zipWith3 branchEqual [1..] branchVars regions

262

259

263 return $

260 return $

264− ex (exprVar:branchVars)

261+ ex (exprVar : map fst branchInfo)

265− (CAnd (exprCon : branchExprCons ++ branchCons))

262+ (CAnd (exprCon : branchExprCons ++ branchCons 2 branchInfo))

266 where

263 where

267 branch patternType (pattern, branchExpr@(A.A branchRegion _)) =

264 branch patternType (pattern, branchExpr@(A.A branchRegion _)) =

268 do branchVar <- variable Flexible

265 do branchVar <- variable Flexible

269 fragment <- Pattern.constrain env pattern patternType

266 fragment <- Pattern.constrain env pattern patternType

270 branchCon <- constrain env branchExpr (varN branchVar)

267 branchCon <- constrain env branchExpr (varN branchVar)

271 return

268 return

272− ( branchVar

273− , branchRegion

269+ ( (branchVar, branchRegion)

274 , CLet [Fragment.toScheme fragment] branchCon

270 , CLet [Fragment.toScheme fragment] branchCon

275 )

271 )

276

272

277− branchEqual n var branchRegion =

273+ branchCons n branchInfo =

274+ case branchInfo of

275+ [] ->

276+ []

277+

278+ (var,_) : [] ->

278− CEqual (Error.CaseBranch n branchRegion) region tipe (varN var)

279+ [ CEqual Error.Case region tipe (varN var) ]

280+

281+ (var,_) : (var',region') : rest ->

282+ let

283+ hint = Error.CaseBranch n region'

284+ con = CEqual hint region (varN var) (varN var')

285+ in

286+ con : branchCons (n+1) ((var', region') : rest)

279

287

280

288

281-- EXPAND PATTERNS

289-- EXPAND PATTERNS