Update internal syntax

Author: natsukagami

docs/_docs/internals/syntax.md

@@ -140,7 +140,7 @@ type      val       var       while     with      yield
 ### Soft keywords
 
 ```
-as  derives  end  extension  infix  inline  opaque  open  throws transparent  using  |  *  +  -
+as  derives  end  erased  extension  infix  inline  opaque  open  throws transparent  using  |  *  +  -
 ```
 
 See the [separate section on soft keywords](../reference/soft-modifier.md) for additional
@@ -180,13 +180,13 @@ Type              ::=  FunType
                     |  FunParamClause ‘=>>’ Type                                TermLambdaTypeTree(ps, t)
                     |  MatchType
                     |  InfixType
-FunType           ::=  FunTypeArgs (‘=>’ | ‘?=>’) Type                          Function(ts, t)
+FunType           ::=  FunTypeArgs (‘=>’ | ‘?=>’) Type                          Function(ts, t) | FunctionWithMods(ts, t, mods, erasedParams)
                     |  HKTypeParamClause '=>' Type                              PolyFunction(ps, t)
 FunTypeArgs       ::=  InfixType
                     |  ‘(’ [ FunArgTypes ] ‘)’
                     |  FunParamClause
 FunParamClause    ::=  ‘(’ TypedFunParam {‘,’ TypedFunParam } ‘)’
-TypedFunParam     ::=  id ‘:’ Type
+TypedFunParam     ::=  [`erased`] id ‘:’ Type
 MatchType         ::=  InfixType `match` <<< TypeCaseClauses >>>
 InfixType         ::=  RefinedType {id [nl] RefinedType}                        InfixOp(t1, op, t2)
 RefinedType       ::=  AnnotType {[nl] Refinement}                              RefinedTypeTree(t, ds)
@@ -207,8 +207,8 @@ Singleton         ::=  SimpleRef
                     |  SimpleLiteral
                     |  Singleton ‘.’ id
 Singletons        ::=  Singleton { ‘,’ Singleton }
-FunArgType        ::=  Type
-                    |  ‘=>’ Type                                                PrefixOp(=>, t)
+FunArgType        ::=  [`erased`] Type
+                    |  [`erased`] ‘=>’ Type                                     PrefixOp(=>, t)
 FunArgTypes       ::=  FunArgType { ‘,’ FunArgType }
 ParamType         ::=  [‘=>’] ParamValueType
 ParamValueType    ::=  [‘into’] ExactParamType                                  Into(t)
@@ -229,7 +229,7 @@ BlockResult       ::=  FunParams (‘=>’ | ‘?=>’) Block
                     |  HkTypeParamClause ‘=>’ Block
                     |  Expr1
 FunParams         ::=  Bindings
-                    |  id
+                    |  [`erased`] id
                     |  ‘_’
 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?)
@@ -369,12 +369,12 @@ DefParamClauses   ::=  {DefParamClause} [[nl] ‘(’ [‘implicit’] DefParams
 DefParamClause    ::=  [nl] ‘(’ DefParams ‘)’ | UsingParamClause
 UsingParamClause  ::=  [nl] ‘(’ ‘using’ (DefParams | FunArgTypes) ‘)’
 DefParams         ::=  DefParam {‘,’ DefParam}
-DefParam          ::=  {Annotation} [‘inline’] Param                            ValDef(mods, id, tpe, expr) -- point of mods at id.
+DefParam          ::=  {Annotation} [`erased`] [‘inline’] Param                            ValDef(mods, id, tpe, expr) -- point of mods at id.
 ```
 
 ### Bindings and Imports
 ```ebnf
-Bindings          ::=  ‘(’ [Binding {‘,’ Binding}] ‘)’
+Bindings          ::=  ‘(’[`erased`] [Binding {‘,’ [`erased`] Binding}] ‘)’
 Binding           ::=  (id | ‘_’) [‘:’ Type]                                    ValDef(_, id, tpe, EmptyTree)
 
 Modifier          ::=  LocalModifier