Merge pull request #9753 from dotty-staging/fix-#9751

nicolasstucki · web-flow · commit 86398747844e · 2020-09-10T10:12:34.000+02:00
Fix #9751: Fix Inline purity checks
diff --git a/compiler/src/dotty/tools/dotc/ast/TreeInfo.scala b/compiler/src/dotty/tools/dotc/ast/TreeInfo.scala
@@ -454,12 +454,14 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
   def refPurity(tree: Tree)(using Context): PurityLevel = {
     val sym = tree.symbol
     if (!tree.hasType) Impure
-    else if (!tree.tpe.widen.isParameterless || sym.isEffectivelyErased) PurePath
+    else if !tree.tpe.widen.isParameterless then PurePath
+    else if sym.is(Erased) then PurePath
     else if tree.tpe.isInstanceOf[ConstantType] then PurePath
     else if (!sym.isStableMember) Impure
     else if (sym.is(Module))
       if (sym.moduleClass.isNoInitsClass) PurePath else IdempotentPath
     else if (sym.is(Lazy)) IdempotentPath
+    else if sym.isAllOf(Inline | Param) then Impure
     else PurePath
   }
 
diff --git a/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala b/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala
@@ -47,7 +47,7 @@ abstract class TransformByNameApply extends MiniPhase { thisPhase: DenotTransfor
             ref(defn.cbnArg).appliedToType(argType).appliedTo(arg).withSpan(arg.span)
           arg match {
             case Apply(Select(qual, nme.apply), Nil)
-            if qual.tpe.derivesFrom(defn.FunctionClass(0)) && isPureExpr(qual) =>
+            if qual.tpe.derivesFrom(defn.FunctionClass(0)) && (isPureExpr(qual) || qual.symbol.isAllOf(Inline | Param)) =>
               wrap(qual)
             case _ =>
               if (isByNameRef(arg) || arg.symbol == defn.cbnArg) arg
diff --git a/compiler/src/dotty/tools/dotc/typer/Inliner.scala b/compiler/src/dotty/tools/dotc/typer/Inliner.scala
@@ -521,7 +521,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
          | Literal(_) =>
         true
       case Ident(_) =>
-        isPureRef(tree)
+        isPureRef(tree) || tree.symbol.isAllOf(Inline | Param)
       case Select(qual, _) =>
         if (tree.symbol.is(Erased)) true
         else isPureRef(tree) && apply(qual)
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -3629,8 +3629,12 @@ 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]
+      && 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 +1,13 @@
+object Test {
+  inline def f(inline x: Boolean): Unit =
+    inline if x then println()
+
+  f(true)
+  f(false)
+
+  inline def g(inline x: => Boolean): Unit =
+    inline if x then println()
+
+  g(true)
+  g(false)
+}
