Change erased syntax

`erased` now follows `given` instead of `implicit`.

Author: odersky

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -106,13 +106,13 @@ class Definitions {
    *  ErasedFunctionN traits follow this template:
    *
    *      trait ErasedFunctionN[T0,...,T{N-1}, R] extends Object {
-   *        def apply(erased $x0: T0, ..., $x{N_1}: T{N-1}): R
+   *        def apply erased ($x0: T0, ..., $x{N_1}: T{N-1}): R
    *      }
    *
    *  ErasedImplicitFunctionN traits follow this template:
    *
    *      trait ErasedImplicitFunctionN[T0,...,T{N-1}, R] extends Object {
-   *        def apply given (erased $x0: T0, ..., $x{N_1}: T{N-1}): R
+   *        def apply given erased ($x0: T0, ..., $x{N_1}: T{N-1}): R
    *      }
    *
    *  ErasedFunctionN and ErasedImplicitFunctionN erase to Function0.

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

@@ -1210,7 +1210,7 @@ object Parsers {
 
     def expr(location: Location.Value): Tree = {
       val start = in.offset
-      if (in.token == IMPLICIT || in.token == ERASED || in.token == GIVEN) {
+      if (closureMods.contains(in.token)) {
         val imods = modifiers(closureMods)
         if (in.token == MATCH) implicitMatch(start, imods)
         else implicitClosure(start, location, imods)
@@ -1994,11 +1994,9 @@ object Parsers {
       normalize(loop(start))
     }
 
-    /** FunArgMods  ::=  { `implicit` | `erased` }
-     *  ClosureMods ::=  { ‘implicit’ | ‘erased’ | ‘given’}
+    /** ClosureMods ::=  { ‘implicit’ | ‘erased’ | ‘given’}
      *  FunTypeMods ::=  { ‘erased’ | ‘given’}
      */
-    val funArgMods: BitSet = BitSet(IMPLICIT, ERASED)
     val closureMods: BitSet = BitSet(GIVEN, IMPLICIT, ERASED)
     val funTypeMods: BitSet = BitSet(GIVEN, ERASED)
 
@@ -2083,11 +2081,12 @@ object Parsers {
     def typeParamClauseOpt(ownerKind: ParamOwner.Value): List[TypeDef] =
       if (in.token == LBRACKET) typeParamClause(ownerKind) else Nil
 
-    /** ClsParamClause    ::=  [nl | ‘with’] `(' [FunArgMods] [ClsParams] ')'
+    /** ClsParamClause    ::=  [nl] [‘erased’] ‘(’ [ClsParams] ‘)’
+     *                      |  ‘given’ [‘erased’] (‘(’ ClsParams ‘)’ | ContextTypes)
      *  ClsParams         ::=  ClsParam {`' ClsParam}
      *  ClsParam          ::=  {Annotation} [{ParamModifier} (`val' | `var') | `inline'] Param
-     *  DefParamClause    ::=  [nl] `(' [FunArgMods] [DefParams] ')' | InferParamClause
-     *  InferParamClause  ::=  ‘given’ (‘(’ DefParams ‘)’ | ContextTypes)
+     *  DefParamClause    ::=  [nl] [‘erased’] ‘(’ [DefParams] ‘)’ | GivenParamClause
+     *  GivenParamClause  ::=  ‘given’ [‘erased’] (‘(’ DefParams ‘)’ | ContextTypes)
      *  ContextTypes      ::=  RefinedType {`,' RefinedType}
      *  DefParams         ::=  DefParam {`,' DefParam}
      *  DefParam          ::=  {Annotation} [`inline'] Param
@@ -2158,17 +2157,10 @@ object Parsers {
 
       // begin paramClause
       inParens {
-      	val isContextual = impliedMods.is(Given)
-        if (in.token == RPAREN && !prefix && !isContextual) Nil
+        if (in.token == RPAREN && !prefix && !impliedMods.is(Given)) Nil
         else {
-          def funArgMods(mods: Modifiers): Modifiers =
-            if (in.token == IMPLICIT && !isContextual)
-              funArgMods(addMod(mods, atSpan(accept(IMPLICIT)) { Mod.Implicit() }))
-            else if (in.token == ERASED)
-              funArgMods(addMod(mods, atSpan(accept(ERASED)) { Mod.Erased() }))
-            else mods
-
-          impliedMods = funArgMods(impliedMods)
+          if (in.token == IMPLICIT && !impliedMods.is(Given | Erased))
+            impliedMods = addMod(impliedMods, atSpan(accept(IMPLICIT)) { Mod.Implicit() })
           val clause =
             if (prefix) param() :: Nil
             else commaSeparated(() => param())
@@ -2178,22 +2170,24 @@ object Parsers {
       }
     }
 
-    /** ClsParamClauses   ::=  {ClsParamClause}
-     *  DefParamClauses   ::=  {DefParamClause}
-     *  InferParamClauses ::=  {InferParamClause}
+    /** ClsParamClauses   ::=  {ClsParamClause} [[nl] ‘(’ [‘implicit’] ClsParams ‘)’]
+     *  DefParamClauses   ::=  {DefParamClause} [[nl] ‘(’ [‘implicit’] DefParams ‘)’]
      *
      *  @return  The parameter definitions
      */
     def paramClauses(ofClass: Boolean = false,
                      ofCaseClass: Boolean = false,
                      ofInstance: Boolean = false): List[List[ValDef]] = {
       def recur(firstClause: Boolean, nparams: Int): List[List[ValDef]] = {
-        val initialMods =
-          if (in.token == GIVEN) {
-            in.nextToken()
-            Modifiers(Given | Implicit)
-          }
-          else EmptyModifiers
+        var initialMods = EmptyModifiers
+        if (in.token == GIVEN) {
+          in.nextToken()
+          initialMods |= Given | Implicit
+        }
+        if (in.token == ERASED) {
+          in.nextToken()
+          initialMods |= Erased
+        }
         val isContextual = initialMods.is(Given)
         newLineOptWhenFollowedBy(LPAREN)
         if (in.token == LPAREN) {
@@ -2617,7 +2611,7 @@ object Parsers {
     }
 
     /** InstanceDef    ::=  [id] InstanceParams InstanceBody
-     *  InstanceParams ::=  [DefTypeParamClause] {InferParamClause}
+     *  InstanceParams ::=  [DefTypeParamClause] {GivenParamClause}
      *  InstanceBody   ::=  [‘of’ ConstrApp {‘,’ ConstrApp }] [TemplateBody]
      *                   |  ‘of’ Type ‘=’ Expr
      */
@@ -2906,7 +2900,7 @@ object Parsers {
         else if (isExprIntro)
           stats += expr(Location.InBlock)
         else if (isDefIntro(localModifierTokens))
-          if (in.token == IMPLICIT || in.token == ERASED || in.token == GIVEN) {
+          if (closureMods.contains(in.token)) {
             val start = in.offset
             var imods = modifiers(closureMods)
             if (isBindingIntro)

compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -185,10 +185,10 @@ class PlainPrinter(_ctx: Context) extends Printer {
         "<noprefix>"
       case tp: MethodType =>
         changePrec(GlobalPrec) {
-          (if (tp.isContextual) " given " else "") ~
-          ("(" + (if (tp.isErasedMethod)   "erased "   else "")
-               + (if (tp.isImplicitMethod && !tp.isContextual) "implicit " else "")
-          ) ~ paramsText(tp) ~
+          (if (tp.isContextual) " given" else "") ~
+          (if (tp.isErasedMethod) " erased" else "") ~~
+          ("(" + (if (tp.isImplicitMethod && !tp.isContextual) "implicit " else "")) ~
+          paramsText(tp) ~
           (if (tp.resultType.isInstanceOf[MethodType]) ")" else "): ") ~
           toText(tp.resultType)
         }

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -136,14 +136,14 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
             atPrec(InfixPrec) { argText(args.head) }
           else
             toTextTuple(args.init)
-        (keywordText("erased ") provided isErased) ~
         (keywordText("given ") provided isContextual) ~
+        (keywordText("erased ") provided isErased) ~
         argStr ~ " => " ~ argText(args.last)
       }
 
     def toTextDependentFunction(appType: MethodType): Text =
-      (keywordText("erased ") provided appType.isErasedMethod) ~
       (keywordText("given ") provided appType.isImplicitMethod) ~
+      (keywordText("erased ") provided appType.isErasedMethod) ~
       "(" ~ paramsText(appType) ~ ") => " ~ toText(appType.resultType)
 
     def isInfixType(tp: Type): Boolean = tp match {

compiler/test-resources/repl/erased

@@ -1,2 +1,2 @@
-scala> def f(erased a: Int): Int = ???
-def f(erased a: Int): Int
+scala> def f erased (a: Int): Int = ???
+def f erased (a: Int): Int

compiler/test-resources/repl/erased-implicit

@@ -1,2 +1,2 @@
-scala> def f(erased implicit a: Int): Int = ???
-def f(erased implicit a: Int): Int
+scala> def f given erased (a: Int): Int = ???
+def f given erased (a: Int): Int

docs/docs/internals/syntax.md

@@ -290,22 +290,21 @@ HkTypeParamClause ::=  ‘[’ HkTypeParam {‘,’ HkTypeParam} ‘]’
 HkTypeParam       ::=  {Annotation} [‘+’ | ‘-’] (Id[HkTypeParamClause] | ‘_’)
                        SubtypeBounds
 
-ClsParamClauses   ::=  {ClsParamClause}
-ClsParamClause    ::=  [nl] ‘(’ [[FunArgMods] ClsParams] ‘)’
-                    |  ‘given’ (‘(’ ([[FunArgMods] ClsParams] ‘)’ | ContextTypes)
+ClsParamClauses   ::=  {ClsParamClause} [[nl] ‘(’ [‘implicit’] ClsParams ‘)’]
+ClsParamClause    ::=  [nl] [‘erased’] ‘(’ [ClsParams] ‘)’
+                    |  ‘given’ [‘erased’] (‘(’ ClsParams ‘)’ | ContextTypes)
 ClsParams         ::=  ClsParam {‘,’ ClsParam}
 ClsParam          ::=  {Annotation}                                             ValDef(mods, id, tpe, expr) -- point of mods on val/var
                        [{Modifier} (‘val’ | ‘var’) | ‘inline’] Param
 Param             ::=  id ‘:’ ParamType [‘=’ Expr]
                     |  INT
 
-DefParamClauses   ::=  {DefParamClause} [[nl] ‘(’ [FunArgMods] DefParams ‘)’]
-DefParamClause    ::=  [nl] ‘(’ [DefParams] ‘)’ | InferParamClause
-InferParamClause  ::=  ‘given’ (‘(’ [DefParams] ‘)’ | ContextTypes)
+DefParamClauses   ::=  {DefParamClause} [[nl] ‘(’ [‘implicit’] DefParams ‘)’]
+DefParamClause    ::=  [nl] [‘erased’] ‘(’ [DefParams] ‘)’ | GivenParamClause
+GivenParamClause  ::=  ‘given’ [‘erased’] (‘(’ DefParams ‘)’ | ContextTypes)
 DefParams         ::=  DefParam {‘,’ DefParam}
 DefParam          ::=  {Annotation} [‘inline’] Param                            ValDef(mods, id, tpe, expr) -- point of mods at id.
 ContextTypes      ::=  RefinedType {‘,’ RefinedType}
-FunArgMods        ::=  { ‘implicit’ | ‘erased’ }
 ClosureMods       ::=  { ‘implicit’ | ‘erased’ | ‘given’}
 ```
 
@@ -379,7 +378,7 @@ ConstrMods        ::=  {Annotation} [AccessModifier]
 ObjectDef         ::=  id [Template]                                            ModuleDef(mods, name, template)  // no constructor
 EnumDef           ::=  id ClassConstr InheritClauses EnumBody                   EnumDef(mods, name, tparams, template)
 InstanceDef       ::=  [id] InstanceParams InstanceBody
-InstanceParams    ::=  [DefTypeParamClause] {InferParamClause}
+InstanceParams    ::=  [DefTypeParamClause] {GivenParamClause}
 InstanceBody      ::=  [‘of’ ConstrApp {‘,’ ConstrApp }] [TemplateBody]
                     |  ‘of’ Type ‘=’ Expr
 Template          ::=  InheritClauses [TemplateBody]                            Template(constr, parents, self, stats)

docs/docs/reference/other-new-features/erased-terms.md

@@ -38,10 +38,10 @@ present in some form in the generated code to be able to do separate compilation
 
 How to define erased terms?
 -------------------------------
-Parameters of methods and functions can be declared as erased, placing `erased` at the start of the parameter list (like `implicit`).
+Parameters of methods and functions can be declared as erased, placing `erased` in front of a parameter list (like `given`).
 
 ```scala
-def methodWithErasedEv(erased ev: Ev): Int = 42
+def methodWithErasedEv erased (ev: Ev): Int = 42
 
 val lambdaWithErasedEv: erased Ev => Int =
   erased (ev: Ev) => 42
@@ -50,10 +50,10 @@ val lambdaWithErasedEv: erased Ev => Int =
 `erased` parameters will not be usable for computations, though they can be used as arguments to other `erased` parameters.
 
 ```scala
-def methodWithErasedInt1(erased i: Int): Int =
+def methodWithErasedInt1 erased (i: Int): Int =
   i + 42 // ERROR: can not use i
 
-def methodWithErasedInt2(erased i: Int): Int =
+def methodWithErasedInt2 erased (i: Int): Int =
   methodWithErasedInt1(i) // OK
 ```
 
@@ -70,7 +70,7 @@ As `erased` are guaranteed not to be used in computations, they can and will be
 
 ```scala
 // becomes def methodWithErasedEv(): Int at runtime
-def methodWithErasedEv(erased ev: Ev): Int = ...
+def methodWithErasedEv erased (ev: Ev): Int = ...
 
 def evidence1: Ev = ...
 erased def erasedEvidence2: Ev = ... // does not exist at runtime
@@ -83,13 +83,13 @@ methodWithErasedEv(evidence1)
 State machine with erased evidence example
 ------------------------------------------
 The following example is an extended implementation of a simple state machine which can be in a state `On` or `Off`.
-The machine can change state from `Off` to `On` with `turnedOn` only if it is currently `Off`, 
+The machine can change state from `Off` to `On` with `turnedOn` only if it is currently `Off`,
 conversely from `On` to `Off` with `turnedOff` only if it is currently `On`. These last constraint are
-captured with the `IsOff[S]` and `IsOn[S]` implicit evidence only exist for `IsOff[Off]` and `IsOn[On]`. 
-For example, not allowing calling `turnedOff` on in an `Off` state as we would require an evidence `IsOn[Off]` 
+captured with the `IsOff[S]` and `IsOn[S]` implicit evidence only exist for `IsOff[Off]` and `IsOn[On]`.
+For example, not allowing calling `turnedOff` on in an `Off` state as we would require an evidence `IsOn[Off]`
 that will not be found.
 
-As the implicit evidences of `turnedOn` and `turnedOff` are not used in the bodies of those functions 
+As the implicit evidences of `turnedOn` and `turnedOff` are not used in the bodies of those functions
 we can mark them as `erased`. This will remove the evidence parameters at runtime, but we would still
 evaluate the `isOn` and `isOff` implicits that were found as arguments.
 As `isOn` and `isOff` are not used except as `erased` arguments, we can mark them as `erased`, hence
@@ -117,9 +117,9 @@ object IsOn {
 }
 
 class Machine[S <: State] private {
-  // ev will disapear from both functions
-  def turnedOn(implicit erased ev: IsOff[S]): Machine[On] = new Machine[On]
-  def turnedOff(implicit erased ev: IsOn[S]): Machine[Off] = new Machine[Off]
+  // ev will disappear from both functions
+  def turnedOn given erased (ev: IsOff[S]): Machine[On] = new Machine[On]
+  def turnedOff given erased (ev: IsOn[S]): Machine[Off] = new Machine[Off]
 }
 
 object Machine {
@@ -156,12 +156,12 @@ Rules
     erased val x = ...
     erased def f = ...
 
-    def g(erased x: Int) = ...
+    def g erased (x: Int) = ...
 
-    (erased x: Int) => ...
+     erased (x: Int) => ...
     def h(x: erased Int => Int) = ...
 
-    class K(erased x: Int) { ... }
+    class K erased (x: Int) { ... }
     ```
 
 
@@ -182,14 +182,14 @@ Rules
 
 4. Eta expansion
 
-   if `def f(erased x: T): U` then `f: (erased T) => U`.
+   if `def f erased (x: T): U` then `f:  erased (T) => U`.
 
 
 5. Erasure Semantics
    * All `erased` parameters are removed from the function
    * All argument to `erased` parameters are not passed to the function
    * All `erased` definitions are removed
-   * All `(erased T1, T2, ..., TN) => R` and `(given erased T1, T2, ..., TN) => R` become `() => R`
+   * All ` erased (T1, T2, ..., TN) => R` and `(given erased T1, T2, ..., TN) => R` become `() => R`
 
 
 6. Overloading
@@ -198,6 +198,6 @@ Rules
 
 
 7. Overriding
-   * Member definitions overidding each other must both be `erased` or not be `erased`
-   * `def foo(x: T): U` cannot be overridden by `def foo(erased x: T): U` an viceversa
+   * Member definitions overriding each other must both be `erased` or not be `erased`
+   * `def foo(x: T): U` cannot be overridden by `def foo erased (x: T): U` an vice-versa
 

tests/fuzzy/5d506217aaf5e71195b85b12ca59245f35152885.scala

@@ -24,7 +24,7 @@ case List(i4: Int) =>
 }
 }
 trait i5 {
-def i3(erased i2: Int): Int = 0
+def i3 erased (i2: Int): Int = 0
 def i2() = { class i3 } match {
 case i4 @ i5 => 1
 case i6: i7 => i5 _ extends i5 =>

tests/generic-java-signatures/erased.scala

@@ -1,5 +1,5 @@
 object MyErased {
-  def f1[U](erased a: Int): Int = 0
+  def f1[U] erased (a: Int): Int = 0
 }
 
 object Test {