Add syntax for dependent function types

Author: odersky

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

@@ -735,6 +735,7 @@ object Parsers {
      *                |  InfixType
      *  FunArgTypes ::=  InfixType
      *                |  `(' [ FunArgType {`,' FunArgType } ] `)'
+     *                |  '(' TypedFunParam {',' TypedFunParam } ')'
      */
     def typ(): Tree = {
       val start = in.offset
@@ -745,6 +746,16 @@ object Parsers {
           val t = typ()
           if (isImplicit) new ImplicitFunction(params, t) else Function(params, t)
         }
+      def funArgTypesRest(first: Tree, following: () => Tree) = {
+        val buf = new ListBuffer[Tree] += first
+        while (in.token == COMMA) {
+          in.nextToken()
+          buf += following()
+        }
+        buf.toList
+      }
+      var isValParamList = false
+
       val t =
         if (in.token == LPAREN) {
           in.nextToken()
@@ -754,10 +765,19 @@ object Parsers {
           }
           else {
             openParens.change(LPAREN, 1)
-            val ts = commaSeparated(funArgType)
+            val paramStart = in.offset
+            val ts = funArgType() match {
+              case Ident(name) if name != tpnme.WILDCARD && in.token == COLON =>
+                isValParamList = true
+                funArgTypesRest(
+                    typedFunParam(paramStart, name.toTermName),
+                    () => typedFunParam(in.offset, ident()))
+              case t =>
+                funArgTypesRest(t, funArgType)
+            }
             openParens.change(LPAREN, -1)
             accept(RPAREN)
-            if (isImplicit || in.token == ARROW) functionRest(ts)
+            if (isImplicit || isValParamList || in.token == ARROW) functionRest(ts)
             else {
               for (t <- ts)
                 if (t.isInstanceOf[ByNameTypeTree])
@@ -790,6 +810,12 @@ object Parsers {
       }
     }
 
+    /** TypedFunParam   ::= id ':' Type */
+    def typedFunParam(start: Offset, name: TermName): Tree = atPos(start) {
+      accept(COLON)
+      makeParameter(name, typ(), Modifiers(Param))
+    }
+
     /** InfixType ::= RefinedType {id [nl] refinedType}
      */
     def infixType(): Tree = infixTypeRest(refinedType())

docs/docs/internals/syntax.md

@@ -122,6 +122,8 @@ Type              ::=  [‘implicit’] FunArgTypes ‘=>’ Type
                     |  InfixType
 FunArgTypes       ::=  InfixType
                     |  ‘(’ [ FunArgType {‘,’ FunArgType } ] ‘)’
+                    |  '(' TypedFunParam {',' TypedFunParam } ')'
+TypedFunParam     ::=  id ':' Type
 InfixType         ::=  RefinedType {id [nl] RefinedType}                        InfixOp(t1, op, t2)
 RefinedType       ::=  WithType {[nl] Refinement}                               RefinedTypeTree(t, ds)
 WithType          ::=  AnnotType {‘with’ AnnotType}                             (deprecated)