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Merged
merged 4 commits into from
Jan 8, 2017
Merged

Topic/533 parse error #1847

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fa9fed6
Add error message for dangling this in path selections
b-studios Dec 21, 2016
ab91bd5
Replace all occurrences of Id, ident or Ident with id
b-studios Dec 21, 2016
09ace25
Give context for code examples to ease understanding
b-studios Jan 7, 2017
feba6a4
Improve error position and drop second error since it is pruned
b-studios Jan 8, 2017
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74 changes: 37 additions & 37 deletions compiler/src/dotty/tools/dotc/parsing/Parsers.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -504,7 +504,7 @@ object Parsers {
def selector(t: Tree): Tree =
atPos(startOffset(t), in.offset) { Select(t, ident()) }

/** Selectors ::= ident { `.' ident()
/** Selectors ::= id { `.' id }
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Good commit. Possible further idea: mention id in the comment for isIdent, also given they're not consistent? So authors of other comments can also find the right terminal name to use in comments?
(Well, being consistent might be even better but I'm not sure what to pick).
But that shouldn't hold this PR.

*
* Accept `.' separated identifiers acting as a selectors on given tree `t`.
* @param finish An alternative parse in case the next token is not an identifier.
Expand All @@ -515,7 +515,7 @@ object Parsers {
if (t1 ne t) t1 else dotSelectors(selector(t), finish)
}

/** DotSelectors ::= { `.' ident()
/** DotSelectors ::= { `.' id }
*
* Accept `.' separated identifiers acting as a selectors on given tree `t`.
* @param finish An alternative parse in case the token following a `.' is not an identifier.
Expand All @@ -528,9 +528,9 @@ object Parsers {
private val id: Tree => Tree = x => x

/** Path ::= StableId
* | [Ident `.'] this
* | [id `.'] this
*
* @param thisOK If true, [Ident `.'] this is acceptable as the path.
* @param thisOK If true, the path can end with the keyword `this`.
* If false, another selection is required after the `this`.
* @param finish An alternative parse in case the token following a `.' is not an identifier.
* If the alternative does not apply, its tree argument is returned unchanged.
Expand All @@ -540,7 +540,7 @@ object Parsers {
def handleThis(qual: Ident) = {
in.nextToken()
val t = atPos(start) { This(qual) }
if (!thisOK && in.token != DOT) syntaxError("`.' expected")
if (!thisOK && in.token != DOT) syntaxError(DanglingThisInPath(), t.pos)
dotSelectors(t, finish)
}
def handleSuper(qual: Ident) = {
Expand All @@ -565,20 +565,20 @@ object Parsers {
}
}

/** MixinQualifier ::= `[' Id `]'
/** MixinQualifier ::= `[' id `]'
*/
def mixinQualifierOpt(): Ident =
if (in.token == LBRACKET) inBrackets(atPos(in.offset) { typeIdent() })
else EmptyTypeIdent

/** StableId ::= Id
* | Path `.' Id
/** StableId ::= id
* | Path `.' id
* | [id '.'] super [`[' id `]']`.' id
*/
def stableId(): Tree =
path(thisOK = false)

/** QualId ::= Id {`.' Id}
/** QualId ::= id {`.' id}
*/
def qualId(): Tree =
dotSelectors(termIdent())
Expand Down Expand Up @@ -773,7 +773,7 @@ object Parsers {
else t

/** SimpleType ::= SimpleType TypeArgs
* | SimpleType `#' Id
* | SimpleType `#' id
* | StableId
* | Path `.' type
* | `(' ArgTypes `)'
Expand Down Expand Up @@ -959,7 +959,7 @@ object Parsers {
/** Expr ::= [`implicit'] FunParams `=>' Expr
* | Expr1
* FunParams ::= Bindings
* | Id
* | id
* | `_'
* ExprInParens ::= PostfixExpr `:' Type
* | Expr
Expand All @@ -975,12 +975,12 @@ object Parsers {
* | `throw' Expr
* | `return' [Expr]
* | ForExpr
* | [SimpleExpr `.'] Id `=' Expr
* | [SimpleExpr `.'] id `=' Expr
* | SimpleExpr1 ArgumentExprs `=' Expr
* | PostfixExpr [Ascription]
* | PostfixExpr `match' `{' CaseClauses `}'
* Bindings ::= `(' [Binding {`,' Binding}] `)'
* Binding ::= (Id | `_') [`:' Type]
* Binding ::= (id | `_') [`:' Type]
* Ascription ::= `:' CompoundType
* | `:' Annotation {Annotation}
* | `:' `_' `*'
Expand Down Expand Up @@ -1124,7 +1124,7 @@ object Parsers {
}

/** FunParams ::= Bindings
* | Id
* | id
* | `_'
* Bindings ::= `(' [Binding {`,' Binding}] `)'
*/
Expand Down Expand Up @@ -1153,7 +1153,7 @@ object Parsers {
(atPos(start) { makeParameter(name, t, mods) }) :: Nil
}

/** Binding ::= (Id | `_') [`:' Type]
/** Binding ::= (id | `_') [`:' Type]
*/
def binding(mods: Modifiers): Tree =
atPos(in.offset) { makeParameter(bindingName(), typedOpt(), mods) }
Expand All @@ -1165,8 +1165,8 @@ object Parsers {
}
else ident()

/** Expr ::= implicit Id `=>' Expr
* BlockResult ::= implicit Id [`:' InfixType] `=>' Block // Scala2 only
/** Expr ::= implicit id `=>' Expr
* BlockResult ::= implicit id [`:' InfixType] `=>' Block // Scala2 only
*/
def implicitClosure(start: Int, location: Location.Value, implicitMods: Modifiers): Tree =
closureRest(start, location, funParams(implicitMods, location))
Expand All @@ -1177,9 +1177,9 @@ object Parsers {
Function(params, if (location == Location.InBlock) block() else expr())
}

/** PostfixExpr ::= InfixExpr [Id [nl]]
/** PostfixExpr ::= InfixExpr [id [nl]]
* InfixExpr ::= PrefixExpr
* | InfixExpr Id [nl] InfixExpr
* | InfixExpr id [nl] InfixExpr
*/
def postfixExpr(): Tree =
infixOps(prefixExpr(), canStartExpressionTokens, prefixExpr, maybePostfix = true)
Expand All @@ -1204,7 +1204,7 @@ object Parsers {
* | xmlLiteral
* | Path
* | `(' [ExprsInParens] `)'
* | SimpleExpr `.' Id
* | SimpleExpr `.' id
* | SimpleExpr (TypeArgs | NamedTypeArgs)
* | SimpleExpr1 ArgumentExprs
*/
Expand Down Expand Up @@ -1456,7 +1456,7 @@ object Parsers {
p
}

/** InfixPattern ::= SimplePattern {Id [nl] SimplePattern}
/** InfixPattern ::= SimplePattern {id [nl] SimplePattern}
*/
def infixPattern(): Tree =
infixOps(simplePattern(), canStartExpressionTokens, simplePattern, notAnOperator = nme.raw.BAR)
Expand All @@ -1468,8 +1468,8 @@ object Parsers {
* | SimplePattern1 [TypeArgs] [ArgumentPatterns]
* SimplePattern1 ::= Path
* | `{' Block `}'
* | SimplePattern1 `.' Id
* PatVar ::= Id
* | SimplePattern1 `.' id
* PatVar ::= id
* | `_'
*/
val simplePattern = () => in.token match {
Expand Down Expand Up @@ -1586,7 +1586,7 @@ object Parsers {
def addMod(mods: Modifiers, mod: Mod): Modifiers =
addFlag(mods, mod.flags).withAddedMod(mod)

/** AccessQualifier ::= "[" (Id | this) "]"
/** AccessQualifier ::= "[" (id | this) "]"
*/
def accessQualifierOpt(mods: Modifiers): Modifiers =
if (in.token == LBRACKET) {
Expand Down Expand Up @@ -1665,16 +1665,16 @@ object Parsers {

/** ClsTypeParamClause::= `[' ClsTypeParam {`,' ClsTypeParam} `]'
* ClsTypeParam ::= {Annotation} [{Modifier} type] [`+' | `-']
* Id [HkTypeParamClause] TypeParamBounds
* id [HkTypeParamClause] TypeParamBounds
*
* DefTypeParamClause::= `[' DefTypeParam {`,' DefTypeParam} `]'
* DefTypeParam ::= {Annotation} Id [HkTypeParamClause] TypeParamBounds
* DefTypeParam ::= {Annotation} id [HkTypeParamClause] TypeParamBounds
*
* TypTypeParamCaluse::= `[' TypTypeParam {`,' TypTypeParam} `]'
* TypTypeParam ::= {Annotation} Id [HkTypePamClause] TypeBounds
* TypTypeParam ::= {Annotation} id [HkTypePamClause] TypeBounds
*
* HkTypeParamClause ::= `[' HkTypeParam {`,' HkTypeParam} `]'
* HkTypeParam ::= {Annotation} ['+' | `-'] (Id[HkTypePamClause] | _') TypeBounds
* HkTypeParam ::= {Annotation} ['+' | `-'] (id [HkTypePamClause] | _') TypeBounds
*/
def typeParamClause(ownerKind: ParamOwner.Value): List[TypeDef] = inBrackets {
def typeParam(): TypeDef = {
Expand Down Expand Up @@ -1829,7 +1829,7 @@ object Parsers {
}
}

/** ImportExpr ::= StableId `.' (Id | `_' | ImportSelectors)
/** ImportExpr ::= StableId `.' (id | `_' | ImportSelectors)
*/
val importExpr = () => path(thisOK = false, handleImport) match {
case imp: Import =>
Expand Down Expand Up @@ -1863,7 +1863,7 @@ object Parsers {
}
}

/** ImportSelector ::= Id [`=>' Id | `=>' `_']
/** ImportSelector ::= id [`=>' id | `=>' `_']
*/
def importSelector(): Tree = {
val from = termIdentOrWildcard()
Expand Down Expand Up @@ -1908,9 +1908,9 @@ object Parsers {
}

/** PatDef ::= Pattern2 {`,' Pattern2} [`:' Type] `=' Expr
* VarDef ::= PatDef | Id {`,' Id} `:' Type `=' `_'
* ValDcl ::= Id {`,' Id} `:' Type
* VarDcl ::= Id {`,' Id} `:' Type
* VarDef ::= PatDef | id {`,' id} `:' Type `=' `_'
* ValDcl ::= id {`,' id} `:' Type
* VarDcl ::= id {`,' id} `:' Type
*/
def patDefOrDcl(start: Offset, mods: Modifiers, docstring: Option[Comment] = None): Tree = atPos(start, nameStart) {
val lhs = commaSeparated(pattern2)
Expand Down Expand Up @@ -2012,8 +2012,8 @@ object Parsers {
Block(stats, Literal(Constant(())))
}

/** TypeDef ::= type Id [TypeParamClause] `=' Type
* TypeDcl ::= type Id [TypeParamClause] TypeBounds
/** TypeDef ::= type id [TypeParamClause] `=' Type
* TypeDcl ::= type id [TypeParamClause] TypeBounds
*/
def typeDefOrDcl(start: Offset, mods: Modifiers, docstring: Option[Comment] = None): Tree = {
newLinesOpt()
Expand Down Expand Up @@ -2055,7 +2055,7 @@ object Parsers {
}
}

/** ClassDef ::= Id [ClsTypeParamClause]
/** ClassDef ::= id [ClsTypeParamClause]
* [ConstrMods] ClsParamClauses TemplateOpt
*/
def classDef(start: Offset, mods: Modifiers, docstring: Option[Comment]): TypeDef = atPos(start, nameStart) {
Expand Down Expand Up @@ -2083,7 +2083,7 @@ object Parsers {
mods
}

/** ObjectDef ::= Id TemplateOpt
/** ObjectDef ::= id TemplateOpt
*/
def objectDef(start: Offset, mods: Modifiers, docstring: Option[Comment] = None): ModuleDef = atPos(start, nameStart) {
val name = ident()
Expand Down
36 changes: 36 additions & 0 deletions compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
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Expand Up @@ -966,4 +966,40 @@ object messages {
| ${"val foo: Int = 3"}
|"""
}

case class DanglingThisInPath()(implicit ctx: Context) extends Message(36) {
val kind = "Syntax"
val msg = hl"""Expected an additional member selection after the keyword ${"this"}"""

val contextCode =
""" trait Outer {
| val member: Int
| type Member
| trait Inner {
| ...
| }
| }"""

val importCode =
""" import Outer.this.member
| // ^^^^^^^"""

val typeCode =
""" type T = Outer.this.Member
| // ^^^^^^^"""

val explanation =
hl"""|Paths of imports and type selections must not end with the keyword ${"this"}.
|
|Maybe you forgot to select a member of ${"this"}? As an example, in the
|following context:
|${contextCode}
|
|- this is a valid import expression using a path
|${importCode}
|
|- this is a valid type using a path
|${typeCode}
|"""
}
}
2 changes: 1 addition & 1 deletion tests/neg/i1845.scala
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@@ -1,3 +1,3 @@
object Test {
type X = FooBar22.this // error
} // error
}