error when postfix and postfixOps not enabled

Author: robstoll

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1677,6 +1677,11 @@ object desugar {
         }
         else {
           assert(ctx.mode.isExpr || ctx.reporter.errorsReported || ctx.mode.is(Mode.Interactive), ctx.mode)
+          if (!ctx.featureEnabled(nme.postFixOps)) {
+            // TODO remove, only here to show that we are in the if-branch
+            println(s"======================================= here but does not error / scala2Compat: ${ctx.scala2CompatMode}")
+            ctx.errorOrMigrationWarning(s"Usage of postfix operator `${op.name}` in: ${t.show} ${op.name}", t.symbol.sourcePos)
+          }
           Select(t, op.name)
         }
       case PrefixOp(op, t) =>

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

@@ -538,6 +538,7 @@ object StdNames {
     val ordinalDollar_ : N      = "_$ordinal"
     val origin: N               = "origin"
     val parts: N                = "parts"
+    val postFixOps: N           = "postFixOps"
     val prefix : N              = "prefix"
     val processEscapes: N       = "processEscapes"
     val productArity: N         = "productArity"

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

@@ -499,7 +499,7 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
         if (!sym.exists) ""
         else toPrefix(sym.owner) + sym.name + "."
       val featureName = toPrefix(owner) + feature
-      ctx.base.settings.language.value exists (s => s == featureName)
+      ctx.base.settings.language.value contains featureName
     }
     hasOption || hasImport
   }

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

@@ -140,7 +140,7 @@ trait Reporting { this: Context =>
   def error(ex: TypeError, pos: SourcePosition): Unit = {
     error(ex.toMessage, pos, sticky = true)
     if (ctx.settings.YdebugTypeError.value)
-      ex.printStackTrace
+      ex.printStackTrace()
   }
 
   def errorOrMigrationWarning(msg: => Message, pos: SourcePosition = NoSourcePosition): Unit =

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

@@ -64,6 +64,12 @@ class CompilationTests extends ParallelTesting {
       compileFile("tests/pos-special/i7575.scala", defaultOptions.and("-language:dynamics")),
       compileFile("tests/pos-special/kind-projector.scala", defaultOptions.and("-Ykind-projector")),
       compileFile("tests/run/i5606.scala", defaultOptions.and("-Yretain-trees")),
+      compileFile("tests/pos-custom-args/i5498-postfixOps.scala", defaultOptions.and("-language:postFixOps")),
+      compileFile(
+        // succeeds because only a warning in Scala2Compat mode
+        "tests/pos-custom-args/i5498-postfixOps.scala",
+        defaultOptions.and("-language:Scala2Compat")
+      ),
     ).checkCompile()
   }
 

tests/neg/i5498-postfixOps.scala

@@ -0,0 +1,5 @@
+import scala.concurrent.duration._
+
+def test() = {
+  1 second
+}

tests/pos-custom-args/i5498-postfixOps.scala

@@ -0,0 +1,5 @@
+import scala.concurrent.duration._
+
+def test() = {
+  1 second
+}