Restore infix named args deprecated syntax detection and migration. Now it only works with -source:3.7-migration, since NamedTuples are stable feature and we don't have ignore experimenal.NamedTuples feature switch

Author: WojciechMazur

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

@@ -669,6 +669,7 @@ object StdNames {
     val readResolve: N          = "readResolve"
     val zero: N                 = "zero"
     val zip: N                  = "zip"
+    val `++` : N                = "++"
     val nothingRuntimeClass: N  = "scala.runtime.Nothing$"
     val nullRuntimeClass: N     = "scala.runtime.Null$"
 

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

@@ -1137,15 +1137,39 @@ object Parsers {
           if (prec < opPrec || leftAssoc && prec == opPrec) {
             opStack = opStack.tail
             recur {
-              atSpan(opInfo.operator.span union opInfo.operand.span union top.span):
-                InfixOp(opInfo.operand, opInfo.operator, top)
+              migrateInfixOp(opInfo, isType):
+                atSpan(opInfo.operator.span union opInfo.operand.span union top.span):
+                  InfixOp(opInfo.operand, opInfo.operator, top)
             }
           }
           else top
         }
       recur(top)
     }
 
+    private def migrateInfixOp(opInfo: OpInfo, isType: Boolean)(infixOp: InfixOp): Tree = {
+      def isNamedTupleOperator = opInfo.operator.name match
+        case nme.EQ | nme.NE |  nme.eq | nme.ne | nme.`++` | nme.zip => true
+        case _ => false
+      if isType then infixOp
+      else infixOp.right match
+        case Tuple(args) if args.exists(_.isInstanceOf[NamedArg]) && !isNamedTupleOperator =>
+          report.errorOrMigrationWarning(DeprecatedInfixNamedArgumentSyntax(), infixOp.right.srcPos, MigrationVersion.AmbiguousNamedTupleSyntax)
+          if MigrationVersion.AmbiguousNamedTupleSyntax.needsPatch then
+            val asApply = cpy.Apply(infixOp)(Select(opInfo.operand, opInfo.operator.name), args)
+            patch(source, infixOp.span, asApply.show(using ctx.withoutColors))
+            asApply // allow to use pre-3.6 syntax in migration mode
+          else infixOp
+        case Parens(assign @ Assign(ident, value)) if !isNamedTupleOperator =>
+          report.errorOrMigrationWarning(DeprecatedInfixNamedArgumentSyntax(), infixOp.right.srcPos, MigrationVersion.AmbiguousNamedTupleSyntax)
+          if MigrationVersion.AmbiguousNamedTupleSyntax.needsPatch then
+            val asApply = cpy.Apply(infixOp)(Select(opInfo.operand, opInfo.operator.name), assign :: Nil)
+            patch(source, infixOp.span, asApply.show(using ctx.withoutColors))
+            asApply // allow to use pre-3.6 syntax in migration mode
+          else infixOp
+        case _ => infixOp
+    }
+
     /** True if we are seeing a lambda argument after a colon of the form:
      *    : (params) =>
      *      body

compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala

@@ -217,7 +217,7 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe
   case NonNamedArgumentInJavaAnnotationID // errorNumber: 201
   case QuotedTypeMissingID // errorNumber: 202
   case DeprecatedAssignmentSyntaxID // errorNumber: 203
-  case DeprecatedInfixNamedArgumentSyntaxID // errorNumber: 204 // no longer emmited
+  case DeprecatedInfixNamedArgumentSyntaxID // errorNumber: 204
   case GivenSearchPriorityID // errorNumber: 205
   case EnumMayNotBeValueClassesID // errorNumber: 206
   case IllegalUnrollPlacementID // errorNumber: 207

compiler/src/dotty/tools/dotc/reporting/messages.scala

@@ -3370,6 +3370,14 @@ final class DeprecatedAssignmentSyntax(key: Name, value: untpd.Tree)(using Conte
 
   override protected def explain(using Context): String = ""
 
+class DeprecatedInfixNamedArgumentSyntax()(using Context) extends SyntaxMsg(DeprecatedInfixNamedArgumentSyntaxID):
+  def msg(using Context) =
+    i"""Deprecated syntax: infix named arguments lists are deprecated; since 3.7 it is interpreted as a single name tuple argument.
+       |To avoid this warning, either remove the argument names or use dotted selection."""
+        + Message.rewriteNotice("This", version = SourceVersion.`3.7-migration`)
+
+  def explain(using Context) = ""
+
 class GivenSearchPriorityWarning(
     pt: Type,
     cmp: Int,

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -79,6 +79,7 @@ class CompilationTests {
       compileFile("tests/rewrites/i20002.scala", defaultOptions.and("-indent", "-rewrite")),
       compileDir("tests/rewrites/annotation-named-pararamters", defaultOptions.and("-rewrite", "-source:3.6-migration")),
       compileFile("tests/rewrites/i21418.scala", unindentOptions.and("-rewrite", "-source:3.5-migration")),
+      compileFile("tests/rewrites/infix-named-args.scala", defaultOptions.and("-rewrite", "-source:3.7-migration")),
       compileFile("tests/rewrites/ambiguous-named-tuple-assignment.scala", defaultOptions.and("-rewrite", "-source:3.6-migration")),
       compileFile("tests/rewrites/i21382.scala", defaultOptions.and("-indent", "-rewrite")),
       compileFile("tests/rewrites/unused.scala", defaultOptions.and("-rewrite", "-Wunused:all")),

tests/neg/infix-named-args.check

@@ -11,3 +11,27 @@
   |           (x: Byte): Int
   |           (x: String): String
   |          match arguments ((x : Int)) (a named tuple)
+-- [E204] Syntax Warning: tests/neg/infix-named-args.scala:2:15 --------------------------------------------------------
+2 |  def f = 42 + (x = 1) // error // werror
+  |               ^^^^^^^
+  |Deprecated syntax: infix named arguments lists are deprecated; since 3.7 it is interpreted as a single name tuple argument.
+  |To avoid this warning, either remove the argument names or use dotted selection.
+  |This can be rewritten automatically under -rewrite -source 3.6-migration.
+-- [E204] Syntax Warning: tests/neg/infix-named-args.scala:5:26 --------------------------------------------------------
+5 |  def g = new C() `multi` (x = 42, y = 27) // werror
+  |                          ^^^^^^^^^^^^^^^^
+  |Deprecated syntax: infix named arguments lists are deprecated; since 3.7 it is interpreted as a single name tuple argument.
+  |To avoid this warning, either remove the argument names or use dotted selection.
+  |This can be rewritten automatically under -rewrite -source 3.6-migration.
+-- [E204] Syntax Warning: tests/neg/infix-named-args.scala:6:21 --------------------------------------------------------
+6 |  def h = new C() ** (x = 42, y = 27) // werror
+  |                     ^^^^^^^^^^^^^^^^
+  |Deprecated syntax: infix named arguments lists are deprecated; since 3.7 it is interpreted as a single name tuple argument.
+  |To avoid this warning, either remove the argument names or use dotted selection.
+  |This can be rewritten automatically under -rewrite -source 3.6-migration.
+-- [E204] Syntax Warning: tests/neg/infix-named-args.scala:13:18 -------------------------------------------------------
+13 |  def f = this ** (x = 2) // werror
+   |                  ^^^^^^^
+   |Deprecated syntax: infix named arguments lists are deprecated; since 3.7 it is interpreted as a single name tuple argument.
+   |To avoid this warning, either remove the argument names or use dotted selection.
+   |This can be rewritten automatically under -rewrite -source 3.6-migration.

tests/rewrites/infix-named-args.check

@@ -0,0 +1,15 @@
+class C:
+  def multi(x: Int, y: Int): Int = x + y
+  def **(x: Int, y: Int): Int = x + y
+  def g = new C().multi(x = 42, y = 27)
+  def h = new C().**(x = 42, y = 27)
+
+type X = (x: Int)
+
+class D(d: Int):
+  def **(x: Int): Int = d * x
+  def **(x: X): Int = d * x.x
+  def f = this.**(x = 2)
+  def g = this ** 2
+  def h = this ** ((x = 2))
+  def i = this.**(x = (1 + 1))

tests/rewrites/infix-named-args.scala

@@ -0,0 +1,15 @@
+class C:
+  def multi(x: Int, y: Int): Int = x + y
+  def **(x: Int, y: Int): Int = x + y
+  def g = new C() `multi` (x = 42, y = 27)
+  def h = new C() ** (x = 42, y = 27)
+
+type X = (x: Int)
+
+class D(d: Int):
+  def **(x: Int): Int = d * x
+  def **(x: X): Int = d * x.x
+  def f = this ** (x = 2)
+  def g = this ** 2
+  def h = this ** ((x = 2))
+  def i = this ** (x = (1 + 1))

tests/warn/infix-named-args-migration.scala

@@ -0,0 +1,15 @@
+//> using options -source:3.7-migration
+
+class C:
+  def f = 42 + (x = 1) // warn // interpreted as 42.+(x = 1) under migration, x is a valid synthetic parameter name
+  def multi(x: Int, y: Int): Int = x + y
+  def **(x: Int, y: Int): Int = x + y
+  def g = new C() `multi` (x = 42, y = 27) // warn
+  def h = new C() ** (x = 42, y = 27) // warn
+
+type X = (x: Int)
+
+class D(d: Int):
+  def **(x: Int): Int = d * x
+  def f = this ** (x = 2) // warn
+  def g = this ** 2