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Alternative Optional Braces Syntax
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* Use `where` to begin template bodies
* Use `do` to begin block expressions
* Use `let <stats> in <blockresult>` as alternative block expression
* Use `with` to begin type refinement bodies
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@mbloms
mbloms committed Dec 10, 2020
1 parent 51ac3ae commit 9638ebf
Showing 1 changed file with 22 additions and 16 deletions.
38 changes: 22 additions & 16 deletions docs/docs/internals/syntax.md
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Expand Up @@ -96,15 +96,15 @@ export extends false final finally for given if
implicit import lazy match new null object package
private protected override return super sealed then throw
trait true try type val var while with
yield
yield let in
: = <- => <: :> # @
=>> ?=>
```

### Soft keywords

```
as derives end extension inline opaque open transparent using
as derives end extension inline opaque open transparent using where
* + -
```

Expand Down Expand Up @@ -142,6 +142,7 @@ Type ::= FunType
| FunParamClause ‘=>>’ Type TermLambdaTypeTree(ps, t)
| MatchType
| InfixType
| StructuralType
FunType ::= FunArgTypes (‘=>’ | ‘?=>’) Type Function(ts, t)
| HKTypeParamClause '=>' Type PolyFunction(ps, t)
FunArgTypes ::= InfixType
Expand All @@ -151,7 +152,8 @@ FunParamClause ::= ‘(’ TypedFunParam {‘,’ TypedFunParam } ‘)’
TypedFunParam ::= id ‘:’ Type
MatchType ::= InfixType `match` ‘{’ TypeCaseClauses ‘}’
InfixType ::= RefinedType {id [nl] RefinedType} InfixOp(t1, op, t2)
RefinedType ::= WithType {[nl] Refinement} RefinedTypeTree(t, ds)
RefinedType ::= WithType [Refinement] RefinedTypeTree(t, ds)
StructuralType ::= ConstrApp {‘with’ ConstrApp} ‘where’ TemplateBody
WithType ::= AnnotType {‘with’ AnnotType} (deprecated)
AnnotType ::= SimpleType {Annotation} Annotated(t, annot)
Expand All @@ -175,7 +177,7 @@ FunArgType ::= Type
ParamType ::= [‘=>’] ParamValueType
ParamValueType ::= Type [‘*’] PostfixOp(t, "*")
TypeArgs ::= ‘[’ Types ‘]’ ts
Refinement ::= ‘{’ [RefineDcl] {semi [RefineDcl]} ‘}’ ds
Refinement ::= [‘with’] [nl] ‘{’ [RefineDcl] {semi [RefineDcl]} ‘}’ ds
TypeBounds ::= [‘>:’ Type] [‘<:’ Type] TypeBoundsTree(lo, hi)
TypeParamBounds ::= TypeBounds {‘:’ Type} ContextBounds(typeBounds, tps)
Types ::= Type {‘,’ Type}
Expand All @@ -193,7 +195,7 @@ FunParams ::= Bindings
Expr1 ::= [‘inline’] ‘if’ ‘(’ Expr ‘)’ {nl} Expr [[semi] ‘else’ Expr] If(Parens(cond), thenp, elsep?)
| [‘inline’] ‘if’ Expr ‘then’ Expr [[semi] ‘else’ Expr] If(cond, thenp, elsep?)
| ‘while’ ‘(’ Expr ‘)’ {nl} Expr WhileDo(Parens(cond), body)
| ‘while’ Expr ‘do’ Expr WhileDo(cond, body)
| ‘while’ Expr DoExpr WhileDo(cond, body)
| ‘try’ Expr Catches [‘finally’ Expr] Try(expr, catches, expr?)
| ‘try’ Expr [‘finally’ Expr] Try(expr, Nil, expr?)
| ‘throw’ Expr Throw(expr)
Expand All @@ -220,9 +222,8 @@ SimpleExpr ::= SimpleRef
| ‘$’ ‘{’ Block ‘}’
| Quoted
| quoteId -- only inside splices
| ‘new’ ConstrApp {‘with’ ConstrApp} New(constr | templ)
[[colonEol] TemplateBody
| ‘new’ [colonEol] TemplateBody
| ‘new’ StructuralType New(constr | templ)
| ‘new’ [‘where’] TemplateBody
| ‘(’ ExprsInParens ‘)’ Parens(exprs)
| SimpleExpr ‘.’ id Select(expr, id)
| SimpleExpr ‘.’ MatchClause
Expand All @@ -240,7 +241,11 @@ ParArgumentExprs ::= ‘(’ [‘using’] ExprsInParens ‘)’
ArgumentExprs ::= ParArgumentExprs
| BlockExpr
BlockExpr ::= ‘{’ (CaseClauses | Block) ‘}’
| DoExpr
| LetExpr
DoExpr ::= ‘do’ ‘{’ Block ‘}’
Block ::= {BlockStat semi} [BlockResult] Block(stats, expr?)
LetExpr ::= ‘let’ {BlockStat semi} ‘in’ BlockResult Block(stats, expr)
BlockStat ::= Import
| {Annotation {nl}} [‘implicit’ | ‘lazy’] Def
| {Annotation {nl}} {LocalModifier} TmplDef
Expand All @@ -250,7 +255,7 @@ BlockStat ::= Import
ForExpr ::= ‘for’ (‘(’ Enumerators ‘)’ | ‘{’ Enumerators ‘}’) ForYield(enums, expr)
{nl} [‘yield’] Expr
| ‘for’ Enumerators (‘do’ Expr | ‘yield’ Expr) ForDo(enums, expr)
| ‘for’ Enumerators (DoExpr | ‘yield’ Expr) ForDo(enums, expr)
Enumerators ::= Generator {semi Enumerator | Guard}
Enumerator ::= Generator
| Guard
Expand Down Expand Up @@ -351,6 +356,7 @@ Export ::= ‘export’ ImportExpr {‘,’ ImportExpr}
EndMarker ::= ‘end’ EndMarkerTag -- when followed by EOL
EndMarkerTag ::= id | ‘if’ | ‘while’ | ‘for’ | ‘match’ | ‘try’
| ‘new’ | ‘this’ | ‘given’ | ‘extension’ | ‘val’
| ‘do’
```

### Declarations and Definitions
Expand Down Expand Up @@ -388,20 +394,20 @@ ClassDef ::= id ClassConstr [Template]
ClassConstr ::= [ClsTypeParamClause] [ConstrMods] ClsParamClauses with DefDef(_, <init>, Nil, vparamss, EmptyTree, EmptyTree) as first stat
ConstrMods ::= {Annotation} [AccessModifier]
ObjectDef ::= id [Template] ModuleDef(mods, name, template) // no constructor
EnumDef ::= id ClassConstr InheritClauses [colonEol] EnumBody
GivenDef ::= [GivenSig] (Type [‘=’ Expr] | StructuralInstance)
EnumDef ::= id ClassConstr InheritClauses [colonEol | ‘where’] EnumBody
GivenDef ::= [GivenSig] (Type [‘=’ Expr])
GivenSig ::= [id] [DefTypeParamClause] {UsingParamClause} ‘:’ -- one of `id`, `DefParamClause`, `UsingParamClause` must be present
StructuralInstance ::= ConstrApp {‘with’ ConstrApp} ‘with’ TemplateBody
Extension ::= ‘extension’ [DefTypeParamClause] ‘(’ DefParam ‘)’
{UsingParamClause}] ExtMethods
ExtMethods ::= ExtMethod | [nl] ‘{’ ExtMethod {semi ExtMethod ‘}’
ExtMethods ::= ExtMethod
| [‘where’] [nl] ‘{’ ExtMethod {semi ExtMethod ‘}’
ExtMethod ::= {Annotation [nl]} {Modifier} ‘def’ DefDef
Template ::= InheritClauses [colonEol] [TemplateBody] Template(constr, parents, self, stats)
Template ::= InheritClauses [[colonEol | ‘where’] TemplateBody] Template(constr, parents, self, stats)
InheritClauses ::= [‘extends’ ConstrApps] [‘derives’ QualId {‘,’ QualId}]
ConstrApps ::= ConstrApp ({‘,’ ConstrApp} | {‘with’ ConstrApp})
ConstrApp ::= SimpleType1 {Annotation} {ParArgumentExprs} Apply(tp, args)
ConstrExpr ::= SelfInvocation
| ‘{’ SelfInvocation {semi BlockStat} ‘}’
| [‘do’] ‘{’ SelfInvocation {semi BlockStat} ‘}’
SelfInvocation ::= ‘this’ ArgumentExprs {ArgumentExprs}
TemplateBody ::= [nl] ‘{’ [SelfType] TemplateStat {semi TemplateStat} ‘}’
Expand Down Expand Up @@ -430,7 +436,7 @@ TopStat ::= Import
| PackageObject
| EndMarker
|
Packaging ::= ‘package’ QualId [nl | colonEol] ‘{’ TopStatSeq ‘}’ Package(qid, stats)
Packaging ::= ‘package’ QualId [nl | colonEol | (‘where’ [nl])] ‘{’ TopStatSeq ‘}’ Package(qid, stats)
PackageObject ::= ‘package’ ‘object’ ObjectDef object with package in mods.
CompilationUnit ::= {‘package’ QualId semi} TopStatSeq Package(qid, stats)
Expand Down

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