Drop given as in instance definitions

Author: odersky

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

@@ -200,7 +200,7 @@ object Parsers {
     def isBindingIntro: Boolean = {
       in.token match {
         case USCORE => true
-        case IDENTIFIER | BACKQUOTED_IDENT => in.lookaheadIn(BitSet(COLON, ARROW))
+        case IDENTIFIER | BACKQUOTED_IDENT => in.lookaheadIn(BitSet(ARROW))
         case LPAREN =>
           val lookahead = in.LookaheadScanner()
           lookahead.skipParens()
@@ -3401,9 +3401,10 @@ object Parsers {
               checkExtensionParams(paramsStart, vparamss)
 
         parseParams(isExtension = !hasGivenSig)
-
+        var oldSyntax = false
         val parents =
           if allowOldGiven && (!newStyle && in.token == FOR || isIdent(nme.as)) then
+            oldSyntax = true
             // for the moment, accept both `delegate for` and `given as`
             in.nextToken()
             tokenSeparated(COMMA, constrApp)
@@ -3421,7 +3422,7 @@ object Parsers {
             tokenSeparated(COMMA, constrApp)
           else Nil
 
-        if allowOldGiven && vparamss.isEmpty then
+        if oldSyntax && vparamss.isEmpty then
           vparamss = paramClauses(ofInstance = true)
 
         val gdef =

tests/disabled/neg-with-compiler/quote-run-in-macro-2/quoted_1.scala

@@ -5,7 +5,7 @@ object Macros {
 
   inline def foo(i: => Int): Int = ${ fooImpl('i) }
   def fooImpl(i: Expr[Int]) given QuoteContext: Expr[Int] = {
-    given as Toolbox = Toolbox.make(getClass.getClassLoader)
+    given Toolbox = Toolbox.make(getClass.getClassLoader)
     val y: Int = run(i)
     y
   }

tests/neg-custom-args/conditionalWarnings.scala

@@ -3,7 +3,7 @@
 object Test {
   @deprecated def foo = ???
 
-  given as Conversion[String, Int] = _.length
+  given Conversion[String, Int] = _.length
 
   foo    // error
 

tests/neg-custom-args/implicit-conversions.scala

@@ -3,19 +3,19 @@ class B
 
 object A {
 
-  given as Conversion[A, B] {
+  given Conversion[A, B] {
     def apply(x: A): B = ???
   }
 
-  given as Conversion[B, A] {
+  given Conversion[B, A] {
     def apply(x: B): A = ???
   }
 }
 
 class C
 
 object D {
-  given as Conversion[A, C] {
+  given Conversion[A, C] {
     def apply(x: A): C = ???
   }
 }

tests/neg-macros/quote-this.scala

@@ -12,12 +12,12 @@ class Foo {
   }
 
   inline def i(): Unit = ${ Foo.impl[Any]('{
-    given as QuoteContext = ???
+    given QuoteContext = ???
     'this // error
   }) }
 
   inline def j(that: Foo): Unit = ${ Foo.impl[Any]('{
-    given as QuoteContext = ???
+    given QuoteContext = ???
     'that // error
   }) }
 

tests/neg-staging/quote-run-in-macro-1/quoted_1.scala

@@ -4,7 +4,7 @@ import given scala.quoted.autolift._
 
 object Macros {
 
-  given as Toolbox = Toolbox.make(getClass.getClassLoader)
+  given Toolbox = Toolbox.make(getClass.getClassLoader)
   inline def foo(i: => Int): Int = ${ fooImpl('i) }
   def fooImpl(i: Expr[Int]) given QuoteContext: Expr[Int] = {
     val y: Int = run(i)

tests/neg-with-compiler/GenericNumLits/Even_1.scala

@@ -29,7 +29,7 @@ object Even {
     def fromDigits(digits: String) = evenFromDigits(digits)
   }
 
-  given as EvenFromDigits {
+  given EvenFromDigits {
     override inline def fromDigits(digits: String) = ${
       evenFromDigitsImpl('digits)
     }

tests/neg/BigFloat/BigFloat_1.scala

@@ -50,15 +50,15 @@ object BigFloat extends App {
     def fromDigits(digits: String) = apply(digits)
   }
 
-  given as BigFloatFromDigits {
+  given BigFloatFromDigits {
     override inline def fromDigits(digits: String) = ${
       fromDigitsImpl('digits)
     }
   }
 
   // Should be in StdLib:
 
-  given as Liftable[BigInt] {
+  given Liftable[BigInt] {
     def toExpr(x: BigInt) =
       '{BigInt(${x.toString.toExpr})}
   }

tests/neg/GenericNumLits/Even_1.scala

@@ -29,7 +29,7 @@ object Even {
     def fromDigits(digits: String) = evenFromDigits(digits)
   }
 
-  given as EvenFromDigits {
+  given EvenFromDigits {
     override inline def fromDigits(digits: String) = ${
       evenFromDigitsImpl('digits)
     }

tests/neg/cannot-reduce-summonFrom.scala

@@ -6,7 +6,7 @@ object Test {
     }
 
   {
-    given as Int = 9
+    given Int = 9
     bar()
   }