Fix infix of match

`match` should have the same precedence as alphanumeric operators. This
means that `a match { ... } + 1` should give a syntax error.

Author: odersky

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

@@ -983,9 +983,15 @@ object Parsers {
         }
         else
           val t = reduceStack(base, top, minPrec, leftAssoc = true, in.name, isType)
-          if !isType && in.token == MATCH then recur(matchClause(t))
+          if !isType && in.token == MATCH then recurAtMinPrec(matchClause(t))
           else t
 
+      def recurAtMinPrec(top: Tree): Tree =
+        if isIdent && isOperator && precedence(in.name) == minInfixPrec
+           || in.token == MATCH
+        then recur(top)
+        else top
+
       recur(first)
     }
 
@@ -2758,8 +2764,8 @@ object Parsers {
     /** OLD: GivenTypes   ::=  AnnotType {‘,’ AnnotType}
      *  NEW: GivenTypes   ::=  Type {‘,’ Type}
      */
-    def givenTypes(newStyle: Boolean, nparams: Int, ofClass: Boolean): List[ValDef] =
-      val tps = commaSeparated(() => if newStyle then typ() else annotType())
+    def givenTypes(nparams: Int, ofClass: Boolean): List[ValDef] =
+      val tps = commaSeparated(typ)
       var counter = nparams
       def nextIdx = { counter += 1; counter }
       val paramFlags = if ofClass then Private | Local | ParamAccessor else Param
@@ -2862,7 +2868,7 @@ object Parsers {
                 || startParamTokens.contains(in.token)
                 || isIdent && (in.name == nme.inline || in.lookaheadIn(BitSet(COLON)))
               if isParams then commaSeparated(() => param())
-              else givenTypes(true, nparams, ofClass)
+              else givenTypes(nparams, ofClass)
           checkVarArgsRules(clause)
           clause
       }

tests/neg/match-infix.scala

@@ -0,0 +1,3 @@
+def f = 1 + 1 match {
+  case 2 => 3
+} + 1   // error // error