Syntax Summary

The following descriptions of Scala tokens uses literal characters ‘c’ when referring to the ASCII fragment \u0000 – \u007F.

Informal descriptions are typeset as “some comment”.

Lexical Syntax

The lexical syntax of Scala is given by the following grammar in EBNF form:

whiteSpace ::= ‘\u0020’ | ‘\u0009’ | ‘\u000D’ | ‘\u000A’ upper ::= ‘A’ | ... | ‘Z’ | ‘$’ and any character in Unicode categories Lu, Lt or Nl, and any character in Unicode categories Lo and Lm that doesn't have contributory property Other_Lowercase lower ::= ‘a’ | ... | ‘z’ | ‘_’ and any character in Unicode category Ll, and any character in Unicode categories Lo or Lm that has contributory property Other_Lowercase letter ::= upper | lower digit ::= ‘0’ | ... | ‘9’ paren ::= ‘(’ | ‘)’ | ‘[’ | ‘]’ | ‘{’ | ‘}’ delim ::= ‘`’ | ‘'’ | ‘"’ | ‘.’ | ‘;’ | ‘,’ opchar ::= ‘!’ | ‘#’ | ‘%’ | ‘&’ | ‘*’ | ‘+’ | ‘-’ | ‘/’ | ‘:’ | ‘<’ | ‘=’ | ‘>’ | ‘?’ | ‘@’ | ‘\’ | ‘^’ | ‘|’ | ‘~’ and any character in Unicode categories Sm or So printableChar ::= all characters in [\u0020, \u007E] inclusive UnicodeEscape ::= ‘\’ ‘u’ {‘u’} hexDigit hexDigit hexDigit hexDigit hexDigit ::= ‘0’ | ... | ‘9’ | ‘A’ | ... | ‘F’ | ‘a’ | ... | ‘f’ charEscapeSeq ::= ‘\’ (‘b’ | ‘t’ | ‘n’ | ‘f’ | ‘r’ | ‘"’ | ‘'’ | ‘\’) escapeSeq ::= UnicodeEscape | charEscapeSeq op ::= opchar {opchar} varid ::= lower idrest boundvarid ::= varid | ‘`’ varid ‘`’ alphaid ::= upper idrest | varid plainid ::= alphaid | op id ::= plainid | ‘`’ { charNoBackQuoteOrNewline | escapeSeq } ‘`’ idrest ::= {letter | digit} [‘_’ op] quoteId ::= ‘'’ alphaid spliceId ::= ‘$’ alphaid ; integerLiteral ::= (decimalNumeral | hexNumeral | binaryNumeral) [‘L’ | ‘l’] decimalNumeral ::= ‘0’ | digit [{digit | ‘_’} digit] hexNumeral ::= ‘0’ (‘x’ | ‘X’) hexDigit [{hexDigit | ‘_’} hexDigit] binaryNumeral ::= ‘0’ (‘b’ | ‘B’) binaryDigit [{binaryDigit | ‘_’} binaryDigit] floatingPointLiteral ::= [decimalNumeral] ‘.’ digit [{digit | ‘_’} digit] [exponentPart] [floatType] | decimalNumeral exponentPart [floatType] | decimalNumeral floatType exponentPart ::= (‘E’ | ‘e’) [‘+’ | ‘-’] digit [{digit | ‘_’} digit] floatType ::= ‘F’ | ‘f’ | ‘D’ | ‘d’ booleanLiteral ::= ‘true’ | ‘false’ characterLiteral ::= ‘'’ (charNoQuoteOrNewline | escapeSeq) ‘'’ stringLiteral ::= ‘"’ {stringElement} ‘"’ | ‘"""’ multiLineChars ‘"""’ stringElement ::= charNoDoubleQuoteOrNewline | escapeSeq multiLineChars ::= {[‘"’] [‘"’] charNoDoubleQuote} {‘"’} interpolatedString ::= alphaid ‘"’ {[‘\’] interpolatedStringPart | ‘\\’ | ‘\"’} ‘"’ | alphaid ‘"""’ {[‘"’] [‘"’] char \ (‘"’ | ‘\$’) | escape} {‘"’} ‘"""’ interpolatedStringPart ::= printableChar \ (‘"’ | ‘$’ | ‘\’) | escape escape ::= ‘\$\$’ | ‘\$"’ | ‘\$’ alphaid | ‘\$’ BlockExpr comment ::= ‘/*’ “any sequence of characters; nested comments are allowed” ‘*/’ | ‘//’ “any sequence of characters up to end of line” nl ::= ´\mathit{“new line character”}´ semi ::= ‘;’ | nl {nl}

Optional Braces

colon ::= ':' -- with side conditions explained in 01-literal-syntax.md <<< ts >>> ::= ‘{’ ts ‘}’ | indent ts outdent :<<< ts >>> ::= [nl] ‘{’ ts ‘}’ | colon indent ts outdent

Context-free Syntax

´\color{red}{\text{TODO SCALA3: Once we're done porting the spec, make sure that the references to grammar productions in the rest of the spec match this.}}´

The context-free syntax of Scala is given by the following EBNF grammar:

RefineDcl ::= ‘val’ ValDcl | ‘def’ DefDcl | ‘type’ {nl} TypeDcl Dcl ::= RefineDcl | ‘var’ VarDcl ValDcl ::= ids ‘:’ Type VarDcl ::= ids ‘:’ Type DefDcl ::= DefSig ‘:’ Type DefSig ::= id [DefTypeParamClause] [TypelessClauses] [DefImplicitClause] TypeDcl ::= id [TypeParamClause] {FunParamClause} TypeBounds Def ::= ‘val’ PatDef | ‘var’ PatDef | ‘def’ DefDef | ‘type’ {nl} TypeDcl | TmplDef PatDef ::= ids [‘:’ Type] ‘=’ Expr | Pattern2 [‘:’ Type] ‘=’ Expr DefDef ::= DefSig [‘:’ Type] ‘=’ Expr | ‘this’ TypelessClauses [DefImplicitClause] ‘=’ ConstrExpr TmplDef ::= ([‘case’] ‘class’ | ‘trait’) ClassDef | [‘case’] ‘object’ ObjectDef | ‘enum’ EnumDef | ‘given’ GivenDef ClassDef ::= id ClassConstr [Template] ClassConstr ::= [ClsTypeParamClause] [ConstrMods] ClsParamClauses ConstrMods ::= {Annotation} [AccessModifier] ObjectDef ::= id [Template] EnumDef ::= id ClassConstr InheritClauses EnumBody GivenDef ::= [GivenSig] (AnnotType [‘=’ Expr] | StructuralInstance) GivenSig ::= [id] [DefTypeParamClause] {UsingParamClause} ‘:’ -- one of `id`, `DefTypeParamClause`, `UsingParamClause` must be present StructuralInstance ::= ConstrApp {‘with’ ConstrApp} [‘with’ WithTemplateBody] Extension ::= ‘extension’ [DefTypeParamClause] {UsingParamClause} ‘(’ DefTermParam ‘)’ {UsingParamClause} ExtMethods ExtMethods ::= ExtMethod | [nl] <<< ExtMethod {semi ExtMethod} >>> ExtMethod ::= {Annotation [nl]} {Modifier} ‘def’ DefDef | Export Template ::= InheritClauses [TemplateBody] InheritClauses ::= [‘extends’ ConstrApps] [‘derives’ QualId {‘,’ QualId}] ConstrApps ::= ConstrApp ({‘,’ ConstrApp} | {‘with’ ConstrApp}) ConstrApp ::= SimpleType1 {Annotation} {ParArgumentExprs} ConstrExpr ::= SelfInvocation | <<< SelfInvocation {semi BlockStat} >>> SelfInvocation ::= ‘this’ ArgumentExprs {ArgumentExprs} WithTemplateBody ::= <<< [SelfType] TemplateStat {semi TemplateStat} >>> TemplateBody ::= :<<< [SelfType] TemplateStat {semi TemplateStat} >>> TemplateStat ::= Import | Export | {Annotation [nl]} {Modifier} Def | {Annotation [nl]} {Modifier} Dcl | Extension | Expr1 | EndMarker | SelfType ::= id [‘:’ InfixType] ‘=>’ | ‘this’ ‘:’ InfixType ‘=>’ EnumBody ::= :<<< [SelfType] EnumStat {semi EnumStat} >>> EnumStat ::= TemplateStat | {Annotation [nl]} {Modifier} EnumCase EnumCase ::= ‘case’ (id ClassConstr [‘extends’ ConstrApps]] | ids) TopStats ::= TopStat {semi TopStat} TopStat ::= Import | Export | {Annotation [nl]} {Modifier} Def | Extension | Packaging | PackageObject | EndMarker | Packaging ::= ‘package’ QualId :<<< TopStats >>> PackageObject ::= ‘package’ ‘object’ ObjectDef CompilationUnit ::= {‘package’ QualId semi} TopStats
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