Fix #9751: Identify inlined trees and make Inline impure

nicolasstucki · nicolasstucki · commit d97fc0422e9a · 2020-09-08T19:20:12.000+02:00
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -3629,8 +3629,13 @@ class Typer extends Namer
     }
 
   private def checkStatementPurity(tree: tpd.Tree)(original: untpd.Tree, exprOwner: Symbol)(using Context): Unit =
-    if (!tree.tpe.isErroneous && !ctx.isAfterTyper && isPureExpr(tree) &&
-        !tree.tpe.isRef(defn.UnitClass) && !isSelfOrSuperConstrCall(tree))
+    if !tree.tpe.isErroneous
+      && !ctx.isAfterTyper
+      && !tree.isInstanceOf[Inlined]
+      && !tree.symbol.isAllOf(Inline | Param)
+      && isPureExpr(tree)
+      && !isSelfOrSuperConstrCall(tree)
+    then
       report.warning(PureExpressionInStatementPosition(original, exprOwner), original.srcPos)
 
   /** Types the body Scala 2 macro declaration `def f = macro <body>` */
diff --git a/tests/neg-custom-args/fatal-warnings/i9751.scala b/tests/neg-custom-args/fatal-warnings/i9751.scala
@@ -0,0 +1,9 @@
+def f(): Unit = {
+  () // error
+  ()
+}
+
+inline def g(): Unit = {
+  () // error
+  ()
+}
diff --git a/tests/pos-special/fatal-warnings/i9751.scala b/tests/pos-special/fatal-warnings/i9751.scala
@@ -0,0 +1,11 @@
+object Test {
+  extension (x: Int)
+    inline def times(inline op: Unit): Unit = {
+      var count = 0
+      while count < x do
+        op
+        count += 1
+    }
+
+  10.times { println("hello") }
+}
diff --git a/tests/pos-special/fatal-warnings/i9751b.scala b/tests/pos-special/fatal-warnings/i9751b.scala
@@ -0,0 +1,7 @@
+object Test {
+  inline def f(inline x: Boolean): Unit =
+    inline if x then println()
+
+  f(true)
+  f(false)
+}
