Change context-free syntax to reflect elimination of = _

Author: odersky

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -3189,7 +3189,8 @@ object Parsers {
 
     /** PatDef  ::=  ids [‘:’ Type] ‘=’ Expr
      *            |  Pattern2 [‘:’ Type] ‘=’ Expr
-     *  VarDef  ::=  PatDef | id {`,' id} `:' Type `=' `_'
+     *  VarDef  ::=  PatDef
+     *            | id {`,' id} `:' Type `=' `_' (deprecated in 3.1)
      *  ValDcl  ::=  id {`,' id} `:' Type
      *  VarDcl  ::=  id {`,' id} `:' Type
      */

docs/docs/internals/syntax.md

@@ -384,14 +384,12 @@ TypeDcl           ::=  id [TypeParamClause] {FunParamClause} TypeBounds
                        [‘=’ Type]
 
 Def               ::=  ‘val’ PatDef
-                    |  ‘var’ VarDef
+                    |  ‘var’ PatDef
                     |  ‘def’ DefDef
                     |  ‘type’ {nl} TypeDcl
                     |  TmplDef
 PatDef            ::=  ids [‘:’ Type] ‘=’ Expr
-                    |  Pattern2 [‘:’ Type] ‘=’ Expr                            PatDef(_, pats, tpe?, expr)
-VarDef            ::=  PatDef
-                    |  ids ‘:’ Type ‘=’ ‘_’
+                    |  Pattern2 [‘:’ Type] ‘=’ Expr                             PatDef(_, pats, tpe?, expr)
 DefDef            ::=  DefSig [‘:’ Type] ‘=’ Expr                               DefDef(_, name, tparams, vparamss, tpe, expr)
                     |  ‘this’ DefParamClause DefParamClauses ‘=’ ConstrExpr     DefDef(_, <init>, Nil, vparamss, EmptyTree, expr | Block)
 

docs/docs/reference/syntax.md

@@ -374,14 +374,12 @@ DefSig            ::=  id [DefTypeParamClause] DefParamClauses
 TypeDcl           ::=  id [TypeParamClause] {FunParamClause} TypeBounds [‘=’ Type]
 
 Def               ::=  ‘val’ PatDef
-                    |  ‘var’ VarDef
+                    |  ‘var’ PatDef
                     |  ‘def’ DefDef
                     |  ‘type’ {nl} TypeDcl
                     |  TmplDef
 PatDef            ::=  ids [‘:’ Type] ‘=’ Expr
                     |  Pattern2 [‘:’ Type] ‘=’ Expr
-VarDef            ::=  PatDef
-                    |  ids ‘:’ Type ‘=’ ‘_’
 DefDef            ::=  DefSig [‘:’ Type] ‘=’ Expr
                     |  ‘this’ DefParamClause DefParamClauses ‘=’ ConstrExpr