Support Scala 3 wildcard and renaming imports under -Xsource:3

src/compiler/scala/tools/nsc/ast/parser/Parsers.scala

@@ -2564,19 +2564,27 @@ self =>
       def loop(expr: Tree): Tree = {
         expr setPos expr.pos.makeTransparent
         val selectors: List[ImportSelector] = in.token match {
-          case USCORE   => List(wildImportSelector()) // import foo.bar._;
-          case LBRACE   => importSelectors()      // import foo.bar.{ x, y, z }
-          case _        =>
-            val nameOffset = in.offset
-            val name = ident()
-            if (in.token == DOT) {
-              // import foo.bar.ident.<unknown> and so create a select node and recurse.
-              val t = atPos(start, if (name == nme.ERROR) in.offset else nameOffset)(Select(expr, name))
-              in.nextToken()
-              return loop(t)
+          case USCORE =>
+            List(wildImportSelector()) // import foo.bar._
+          case IDENTIFIER if currentRun.isScala3 && in.name == raw.STAR =>
+            List(wildImportSelector()) // import foo.bar.*
+          case LBRACE =>
+            importSelectors()          // import foo.bar.{ x, y, z }
+          case _ =>
+            if (settings.isScala3 && lookingAhead { isRawIdent && in.name == nme.as })
+              List(importSelector())  // import foo.bar as baz
+            else {
+              val nameOffset = in.offset
+              val name = ident()
+              if (in.token == DOT) {
+                // import foo.bar.ident.<unknown> and so create a select node and recurse.
+                val t = atPos(start, if (name == nme.ERROR) in.offset else nameOffset)(Select(expr, name))
+                in.nextToken()
+                return loop(t)
+              }
+              // import foo.bar.Baz;
+              else List(makeImportSelector(name, nameOffset))
             }
-            // import foo.bar.Baz;
-            else List(makeImportSelector(name, nameOffset))
         }
         // reaching here means we're done walking.
         atPos(start)(Import(expr, selectors))
@@ -2619,17 +2627,20 @@ self =>
       val bbq          = in.token == BACKQUOTED_IDENT
       val name         = wildcardOrIdent()
       var renameOffset = -1
-      val rename       = in.token match {
-        case ARROW =>
+
+      val rename =
+        if (in.token == ARROW || (settings.isScala3 && isRawIdent && in.name == nme.as)) {
           in.nextToken()
           renameOffset = in.offset
           if (name == nme.WILDCARD && !bbq) syntaxError(renameOffset, "Wildcard import cannot be renamed")
           wildcardOrIdent()
-        case _ if name == nme.WILDCARD && !bbq => null
-        case _     =>
+        }
+        else if (name == nme.WILDCARD && !bbq) null
+        else {
           renameOffset = start
           name
-      }
+        }
+
       ImportSelector(name, start, rename, renameOffset)
     }
 

src/reflect/scala/reflect/internal/StdNames.scala

@@ -658,6 +658,9 @@ trait StdNames {
     val long2Long: NameType       = nameType("long2Long")
     val boolean2Boolean: NameType = nameType("boolean2Boolean")
 
+    // Scala 3 import syntax
+    val as: NameType              = nameType("as")
+
     // Compiler utilized names
 
     val AnnotatedType: NameType        = nameType("AnnotatedType")

test/files/neg/import-future.check

@@ -0,0 +1,4 @@
+import-future.scala:15: error: not found: value unrelated
+    unrelated(1) // error
+    ^
+1 error

test/files/neg/import-future.scala

@@ -0,0 +1,27 @@
+// scalac: -Xsource:3
+//
+
+class D {
+  def *(y: Int): Int = y
+  def unrelated(y: Int): Int = y
+}
+
+object Test {
+  val d = new D
+
+  def one: Int = {
+    import d.`*`
+
+    unrelated(1) // error
+
+    *(1)
+  }
+
+  def two: Int = {
+    import d.*
+
+    unrelated(1)
+
+    *(1)
+  }
+}

test/files/pos/import-future.scala

@@ -0,0 +1,25 @@
+// scalac: -Xsource:3
+//
+
+import java.io as jio
+import scala.{collection as c}
+
+import c.mutable as mut
+import mut.ArrayBuffer as Buf
+
+object O {
+  val x: jio.IOException = ???
+  val y = Buf(1, 2, 3)
+
+  type OString = String
+  def foo22(x: Int) = x
+}
+
+class C {
+  import O.{ foo22 as foo, OString as OS }
+  println(foo(22))
+  val s: OS = ""
+
+  import mut.*
+  val ab = ArrayBuffer(1)
+}