Scala 3 語法摘要
下列 Scala 權杖描述在參照 ASCII 片段 \u0000 – \u007F 時使用字面字元 ‘c’。
非正式描述排版為 “一些註解”。
字彙語法
Scala 的字彙語法由 EBNF 形式中的下列語法提供
whiteSpace ::= ‘\u0020’ | ‘\u0009’ | ‘\u000D’ | ‘\u000A’
upper ::= ‘A’ | ... | ‘Z’ | ‘$’ and any character in Unicode categories Lu, Lt or Nl,
and any character in Unicode categories Lo and Lm that doesn't have
contributory property Other_Lowercase
lower ::= ‘a’ | ... | ‘z’ | ‘_’ and any character in Unicode category Ll,
and any character in Unicode categories Lo or Lm that has contributory
property Other_Lowercase
letter ::= upper | lower
digit ::= ‘0’ | ... | ‘9’
paren ::= ‘(’ | ‘)’ | ‘[’ | ‘]’ | ‘{’ | ‘}’
delim ::= ‘`’ | ‘'’ | ‘"’ | ‘.’ | ‘;’ | ‘,’
opchar ::= ‘!’ | ‘#’ | ‘%’ | ‘&’ | ‘*’ | ‘+’ | ‘-’ | ‘/’ | ‘:’ |
‘<’ | ‘=’ | ‘>’ | ‘?’ | ‘@’ | ‘\’ | ‘^’ | ‘|’ | ‘~’
and any character in Unicode categories Sm or So
printableChar ::= all characters in [\u0020, \u007E] inclusive
UnicodeEscape ::= ‘\’ ‘u’ {‘u’} hexDigit hexDigit hexDigit hexDigit
hexDigit ::= ‘0’ | ... | ‘9’ | ‘A’ | ... | ‘F’ | ‘a’ | ... | ‘f’
charEscapeSeq ::= ‘\’ (‘b’ | ‘t’ | ‘n’ | ‘f’ | ‘r’ | ‘"’ | ‘'’ | ‘\’)
escapeSeq ::= UnicodeEscape | charEscapeSeq
op ::= opchar {opchar}
varid ::= lower idrest
boundvarid ::= varid
| ‘`’ varid ‘`’
plainid ::= alphaid
| op
id ::= plainid
| ‘`’ { charNoBackQuoteOrNewline | escapeSeq } ‘`’
idrest ::= {letter | digit} [‘_’ op]
quoteId ::= ‘'’ alphaid
spliceId ::= ‘$’ alphaid ;
integerLiteral ::= (decimalNumeral | hexNumeral) [‘L’ | ‘l’]
decimalNumeral ::= ‘0’ | digit [{digit | ‘_’} digit]
hexNumeral ::= ‘0’ (‘x’ | ‘X’) hexDigit [{hexDigit | ‘_’} hexDigit]
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
alphaid ::= upper idrest
| varid
comment ::= ‘/*’ “any sequence of characters; nested comments are allowed” ‘*/’
| ‘//’ “any sequence of characters up to end of line”
nl ::= “new line character”
semi ::= ‘;’ | nl {nl}
可選大括號
可選大括號的原則是任何可以接續 { 的關鍵字也可以接續縮排區塊，而不需要插入 :。（允許可選 : 會適得其反，因為它會引進多種執行相同動作的方法。）
字彙分析器會插入表示縮排程式碼區塊的 indent 和 outdent 權杖 在特定點。
在下列上下文無關產生式中，我們使用符號 <<< ts >>> 來表示權杖序列 ts，它會封裝在大括號 { ts } 中或構成縮排區塊 indent ts outdent。類似的，符號 :<<< ts >>> 表示權杖序列 ts，它會封裝在大括號 { ts } 中或構成縮排區塊 indent ts outdent，並接續 colon 權杖。
colon 權杖讀取為標準冒號 ":"，但會在 colon 根據上下文無關語法合法時產生，但僅限於前一個權杖是字母數字識別碼、反引號識別碼或下列權杖之一：this、super、new、")" 和 "]"。
colon ::= ':' -- with side conditions explained above
<<< ts >>> ::= ‘{’ ts ‘}’
| indent ts outdent
:<<< ts >>> ::= [nl] ‘{’ ts ‘}’
| colon indent ts outdent
關鍵字
常規關鍵字
abstract case catch class def do else
enum export extends false final finally for
given if implicit import lazy match new
null object override package private protected return
sealed super then throw trait true try
type val var while with yield
: = <- => <: >: #
@ =>> ?=>
軟關鍵字
as derives end extension infix inline opaque open transparent using | * + -
請參閱軟關鍵字的單獨部分，以取得有關在何處識別軟關鍵字的其他詳細資訊。
無關脈絡語法
Scala 的無關脈絡語法由下列 EBNF 語法提供
文字和路徑
SimpleLiteral ::= [‘-’] integerLiteral
| [‘-’] floatingPointLiteral
| booleanLiteral
| characterLiteral
| stringLiteral
Literal ::= SimpleLiteral
| interpolatedStringLiteral
| symbolLiteral
| ‘null’
QualId ::= id {‘.’ id}
ids ::= id {‘,’ id}
SimpleRef ::= id
| [id ‘.’] ‘this’
| [id ‘.’] ‘super’ [ClassQualifier] ‘.’ id
ClassQualifier ::= ‘[’ id ‘]’
類型
Type ::= FunType
| HkTypeParamClause ‘=>>’ Type
| FunParamClause ‘=>>’ Type
| MatchType
| InfixType
FunType ::= FunTypeArgs (‘=>’ | ‘?=>’) Type
| HKTypeParamClause '=>' Type
FunTypeArgs ::= InfixType
| ‘(’ [ FunArgTypes ] ‘)’
| FunParamClause
FunParamClause ::= ‘(’ TypedFunParam {‘,’ TypedFunParam } ‘)’
TypedFunParam ::= id ‘:’ Type
MatchType ::= InfixType `match` <<< TypeCaseClauses >>>
InfixType ::= RefinedType {id [nl] RefinedType}
RefinedType ::= AnnotType {[nl] Refinement}
AnnotType ::= SimpleType {Annotation}
SimpleType ::= SimpleLiteral
| ‘?’ TypeBounds
| id
| Singleton ‘.’ id
| Singleton ‘.’ ‘type’
| ‘(’ Types ‘)’
| Refinement
| SimpleType1 TypeArgs
| SimpleType1 ‘#’ id
Singleton ::= SimpleRef
| SimpleLiteral
| Singleton ‘.’ id
FunArgType ::= Type
| ‘=>’ Type
FunArgTypes ::= FunArgType { ‘,’ FunArgType }
ParamType ::= [‘=>’] ParamValueType
ParamValueType ::= Type [‘*’]
TypeArgs ::= ‘[’ Types ‘]’
Refinement ::= :<<< [RefineDcl] {semi [RefineDcl]} >>>
TypeBounds ::= [‘>:’ Type] [‘<:’ Type]
TypeParamBounds ::= TypeBounds {‘:’ Type}
Types ::= Type {‘,’ Type}
運算式
Expr ::= FunParams (‘=>’ | ‘?=>’) Expr
| HkTypeParamClause ‘=>’ Expr
| Expr1
BlockResult ::= FunParams (‘=>’ | ‘?=>’) Block
| HkTypeParamClause ‘=>’ Block
| Expr1
FunParams ::= Bindings
| id
| ‘_’
Expr1 ::= [‘inline’] ‘if’ ‘(’ Expr ‘)’ {nl} Expr [[semi] ‘else’ Expr]
| [‘inline’] ‘if’ Expr ‘then’ Expr [[semi] ‘else’ Expr]
| ‘while’ ‘(’ Expr ‘)’ {nl} Expr
| ‘while’ Expr ‘do’ Expr
| ‘try’ Expr Catches [‘finally’ Expr]
| ‘try’ Expr [‘finally’ Expr]
| ‘throw’ Expr
| ‘return’ [Expr]
| ForExpr
| [SimpleExpr ‘.’] id ‘=’ Expr
| PrefixOperator SimpleExpr ‘=’ Expr
| SimpleExpr ArgumentExprs ‘=’ Expr
| PostfixExpr [Ascription]
| ‘inline’ InfixExpr MatchClause
Ascription ::= ‘:’ InfixType
| ‘:’ Annotation {Annotation}
Catches ::= ‘catch’ (Expr | ExprCaseClause)
PostfixExpr ::= InfixExpr [id] -- only if language.postfixOperators is enabled
InfixExpr ::= PrefixExpr
| InfixExpr id [nl] InfixExpr
| InfixExpr id ColonArgument
| InfixExpr MatchClause
MatchClause ::= ‘match’ <<< CaseClauses >>>
PrefixExpr ::= [PrefixOperator] SimpleExpr
PrefixOperator ::= ‘-’ | ‘+’ | ‘~’ | ‘!’ -- unless backquoted
SimpleExpr ::= SimpleRef
| Literal
| ‘_’
| BlockExpr
| ExprSplice
| Quoted
| quoteId -- only inside splices
| ‘new’ ConstrApp {‘with’ ConstrApp} [TemplateBody]
| ‘new’ TemplateBody
| ‘(’ ExprsInParens ‘)’
| SimpleExpr ‘.’ id
| SimpleExpr ‘.’ MatchClause
| SimpleExpr TypeArgs
| SimpleExpr ArgumentExprs
| SimpleExpr ColonArgument
ColonArgument ::= colon [LambdaStart]
indent (CaseClauses | Block) outdent
LambdaStart ::= FunParams (‘=>’ | ‘?=>’)
| HkTypeParamClause ‘=>’
Quoted ::= ‘'’ ‘{’ Block ‘}’
| ‘'’ ‘[’ TypeBlock ‘]’
ExprSplice ::= spliceId -- if inside quoted block
| ‘$’ ‘{’ Block ‘}’ -- unless inside quoted pattern
| ‘$’ ‘{’ Pattern ‘}’ -- when inside quoted pattern
ExprsInParens ::= ExprInParens {‘,’ ExprInParens}
ExprInParens ::= PostfixExpr ‘:’ Type
| Expr
ParArgumentExprs ::= ‘(’ [ExprsInParens] ‘)’
| ‘(’ ‘using’ ExprsInParens ‘)’
| ‘(’ [ExprsInParens ‘,’] PostfixExpr ‘*’ ‘)’
ArgumentExprs ::= ParArgumentExprs
| BlockExpr
BlockExpr ::= <<< (CaseClauses | Block) >>>
Block ::= {BlockStat semi} [BlockResult]
BlockStat ::= Import
| {Annotation {nl}} {LocalModifier} Def
| Extension
| Expr1
| EndMarker
TypeBlock ::= {TypeBlockStat semi} Type
TypeBlockStat ::= ‘type’ {nl} TypeDcl
ForExpr ::= ‘for’ ‘(’ Enumerators0 ‘)’ {nl} [‘do‘ | ‘yield’] Expr
| ‘for’ ‘{’ Enumerators0 ‘}’ {nl} [‘do‘ | ‘yield’] Expr
| ‘for’ Enumerators0 (‘do‘ | ‘yield’) Expr
Enumerators0 ::= {nl} Enumerators [semi]
Enumerators ::= Generator {semi Enumerator | Guard}
Enumerator ::= Generator
| Guard {Guard}
| Pattern1 ‘=’ Expr
Generator ::= [‘case’] Pattern1 ‘<-’ Expr
Guard ::= ‘if’ PostfixExpr
CaseClauses ::= CaseClause { CaseClause }
CaseClause ::= ‘case’ Pattern [Guard] ‘=>’ Block
ExprCaseClause ::= ‘case’ Pattern [Guard] ‘=>’ Expr
TypeCaseClauses ::= TypeCaseClause { TypeCaseClause }
TypeCaseClause ::= ‘case’ (InfixType | ‘_’) ‘=>’ Type [semi]
Pattern ::= Pattern1 { ‘|’ Pattern1 }
Pattern1 ::= PatVar ‘:’ RefinedType
| [‘-’] integerLiteral ‘:’ RefinedType
| [‘-’] floatingPointLiteral ‘:’ RefinedType
| Pattern2
Pattern2 ::= [id ‘@’] InfixPattern
InfixPattern ::= SimplePattern { id [nl] SimplePattern }
SimplePattern ::= PatVar
| Literal
| ‘(’ [Patterns] ‘)’
| Quoted
| SimplePattern1 [TypeArgs] [ArgumentPatterns]
| ‘given’ RefinedType
SimplePattern1 ::= SimpleRef
| SimplePattern1 ‘.’ id
PatVar ::= varid
| ‘_’
Patterns ::= Pattern {‘,’ Pattern}
ArgumentPatterns ::= ‘(’ [Patterns] ‘)’
| ‘(’ [Patterns ‘,’] PatVar ‘*’ ‘)’
類型和值參數
ClsTypeParamClause::= ‘[’ ClsTypeParam {‘,’ ClsTypeParam} ‘]’
ClsTypeParam ::= {Annotation} [‘+’ | ‘-’] id [HkTypeParamClause] TypeParamBounds
TypTypeParamClause::= ‘[’ TypTypeParam {‘,’ TypTypeParam} ‘]’
TypTypeParam ::= {Annotation} id [HkTypeParamClause] TypeBounds
HkTypeParamClause ::= ‘[’ HkTypeParam {‘,’ HkTypeParam} ‘]’
HkTypeParam ::= {Annotation} [‘+’ | ‘-’] (id [HkTypeParamClause] | ‘_’) TypeBounds
ClsParamClauses ::= {ClsParamClause} [[nl] ‘(’ [‘implicit’] ClsParams ‘)’]
ClsParamClause ::= [nl] ‘(’ ClsParams ‘)’
| [nl] ‘(’ ‘using’ (ClsParams | FunArgTypes) ‘)’
ClsParams ::= ClsParam {‘,’ ClsParam}
ClsParam ::= {Annotation} [{Modifier} (‘val’ | ‘var’) | ‘inline’] Param
TypelessClauses ::= TypelessClause {TypelessClause}
TypelessClause ::= DefTermParamClause
| UsingParamClause
DefTypeParamClause::= [nl] ‘[’ DefTypeParam {‘,’ DefTypeParam} ‘]’
DefTypeParam ::= {Annotation} id [HkTypeParamClause] TypeParamBounds
DefTermParamClause::= [nl] ‘(’ [DefTermParams] ‘)’
UsingParamClause ::= [nl] ‘(’ ‘using’ (DefTermParams | FunArgTypes) ‘)’
DefImplicitClause ::= [nl] ‘(’ ‘implicit’ DefTermParams ‘)’
DefTermParams ::= DefTermParam {‘,’ DefTermParam}
DefTermParam ::= {Annotation} [‘inline’] Param
Param ::= id ‘:’ ParamType [‘=’ Expr]
繫結和匯入
Bindings ::= ‘(’ [Binding {‘,’ Binding}] ‘)’
Binding ::= (id | ‘_’) [‘:’ Type]
Modifier ::= LocalModifier
| AccessModifier
| ‘override’
| ‘opaque’
LocalModifier ::= ‘abstract’
| ‘final’
| ‘sealed’
| ‘open’
| ‘implicit’
| ‘lazy’
| ‘inline’
AccessModifier ::= (‘private’ | ‘protected’) [AccessQualifier]
AccessQualifier ::= ‘[’ id ‘]’
Annotation ::= ‘@’ SimpleType1 {ParArgumentExprs}
Import ::= ‘import’ ImportExpr {‘,’ ImportExpr}
Export ::= ‘export’ ImportExpr {‘,’ ImportExpr}
ImportExpr ::= SimpleRef {‘.’ id} ‘.’ ImportSpec
| SimpleRef ‘as’ id
ImportSpec ::= NamedSelector
| WildCardSelector
| ‘{’ ImportSelectors) ‘}’
NamedSelector ::= id [‘as’ (id | ‘_’)]
WildCardSelector ::= ‘*’ | ‘given’ [InfixType]
ImportSelectors ::= NamedSelector [‘,’ ImportSelectors]
| WildCardSelector {‘,’ WildCardSelector}
EndMarker ::= ‘end’ EndMarkerTag -- when followed by EOL
EndMarkerTag ::= id | ‘if’ | ‘while’ | ‘for’ | ‘match’ | ‘try’
| ‘new’ | ‘this’ | ‘given’ | ‘extension’ | ‘val’
宣告和定義
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
在本文中