Scala.js: Handle SAMs for js.ThisFunction's.

Author: sjrd

compiler/src/dotty/tools/backend/sjs/JSCodeGen.scala

@@ -2472,20 +2472,34 @@ class JSCodeGen()(using genCtx: Context) {
       box(call, sym.info.finalResultType)
     }
 
-    val closure = js.Closure(arrow = true, formalCaptures, formalParams, genBody, actualCaptures)
-    report.debuglog(closure.toString)
-
     val funInterfaceSym = functionalInterface.tpe.widenDealias.typeSymbol
-    if (jsdefn.isJSFunctionClass(funInterfaceSym)) {
-      closure
+
+    if (jsdefn.isJSThisFunctionClass(funInterfaceSym)) {
+      val thisParam :: otherParams = formalParams
+      js.Closure(
+          arrow = false,
+          formalCaptures,
+          otherParams,
+          js.Block(
+              js.VarDef(thisParam.name, thisParam.originalName,
+                  thisParam.ptpe, mutable = false,
+                  js.This()(thisParam.ptpe)(thisParam.pos))(thisParam.pos),
+              genBody),
+          actualCaptures)
     } else {
-      assert(!funInterfaceSym.exists || defn.isFunctionClass(funInterfaceSym),
-          s"Invalid functional interface $funInterfaceSym reached the back-end")
-      val formalCount = formalParams.size
-      val cls = ClassName("scala.scalajs.runtime.AnonFunction" + formalCount)
-      val ctorName = MethodName.constructor(
-          jstpe.ClassRef(ClassName("scala.scalajs.js.Function" + formalCount)) :: Nil)
-      js.New(cls, js.MethodIdent(ctorName), List(closure))
+      val closure = js.Closure(arrow = true, formalCaptures, formalParams, genBody, actualCaptures)
+
+      if (jsdefn.isJSFunctionClass(funInterfaceSym)) {
+        closure
+      } else {
+        assert(!funInterfaceSym.exists || defn.isFunctionClass(funInterfaceSym),
+            s"Invalid functional interface $funInterfaceSym reached the back-end")
+        val formalCount = formalParams.size
+        val cls = ClassName("scala.scalajs.runtime.AnonFunction" + formalCount)
+        val ctorName = MethodName.constructor(
+            jstpe.ClassRef(ClassName("scala.scalajs.js.Function" + formalCount)) :: Nil)
+        js.New(cls, js.MethodIdent(ctorName), List(closure))
+      }
     }
   }
 

compiler/src/dotty/tools/dotc/config/SJSPlatform.scala

@@ -13,6 +13,7 @@ class SJSPlatform()(using Context) extends JavaPlatform {
 
   /** Is the SAMType `cls` also a SAM under the rules of the Scala.js back-end? */
   override def isSam(cls: ClassSymbol)(using Context): Boolean =
-    defn.isFunctionClass(cls) || jsDefinitions.isJSFunctionClass(cls)
+    defn.isFunctionClass(cls)
+      || jsDefinitions.isJSFunctionClass(cls)
+      || jsDefinitions.isJSThisFunctionClass(cls)
 }
-

project/Build.scala

@@ -1094,9 +1094,8 @@ object Build {
             -- "NestedJSClassTest.scala" // non-native JS classes
             -- "NonNativeJSTypeTest.scala" // non-native JS classes
             -- "PromiseMock.scala" // non-native JS classes
-            -- "SpecialTest.scala" // assertion error in ExpandSAMs
+            -- "SpecialTest.scala" // not yet implemented JS-specific primitive
             -- "SymbolTest.scala" // IR checking errors
-            -- "ThisFunctionTest.scala" // assertion error in ExpandSAMs
             -- "UndefOrTest.scala" // StackOverflow in the compiler
             )).get
 
@@ -1118,11 +1117,7 @@ object Build {
 
           ++ (dir / "js/src/test/scala/org/scalajs/testsuite/niobuffer" ** "*.scala").get
           ++ (dir / "js/src/test/scala/org/scalajs/testsuite/scalalib" ** "*.scala").get
-
-          ++ (dir / "js/src/test/scala/org/scalajs/testsuite/typedarray" ** (("*.scala": FileFilter)
-            -- "TypedArrayTest.scala" // assertion error in ExpandSAMs
-            )).get
-
+          ++ (dir / "js/src/test/scala/org/scalajs/testsuite/typedarray" ** "*.scala").get
           ++ (dir / "js/src/test/scala/org/scalajs/testsuite/utils" ** "*.scala").get
 
           ++ (dir / "js/src/test/require-2.12" ** (("*.scala": FileFilter)