Merge pull request scala#2175 from retronym/ticket/7185

SI-7185 Avoid NPE in TreeInfo.isExprSafeToInline

Author: paulp

src/reflect/scala/reflect/internal/TreeInfo.scala

@@ -98,7 +98,8 @@ abstract class TreeInfo {
       // However, before typing, applications of nullary functional values are also
       // Apply(function, Nil) trees. To prevent them from being treated as pure,
       // we check that the callee is a method.
-      fn.symbol.isMethod && !fn.symbol.isLazy && isExprSafeToInline(fn)
+      // The callee might also be a Block, which has a null symbol, so we guard against that (SI-7185)
+      fn.symbol != null && fn.symbol.isMethod && !fn.symbol.isLazy && isExprSafeToInline(fn)
     case Typed(expr, _) =>
       isExprSafeToInline(expr)
     case Block(stats, expr) =>

test/files/neg/t7185.check

@@ -0,0 +1,7 @@
+t7185.scala:2: error: overloaded method value apply with alternatives:
+  (f: scala.xml.Node => Boolean)scala.xml.NodeSeq <and>
+  (i: Int)scala.xml.Node
+ cannot be applied to ()
+  <e></e>()
+   ^
+one error found

test/files/neg/t7185.scala

@@ -0,0 +1,3 @@
+object Test {
+  <e></e>()
+}

test/files/run/t7185.check

@@ -0,0 +1,34 @@
+Type in expressions to have them evaluated.
+Type :help for more information.
+
+scala> 
+
+scala> import scala.tools.reflect.ToolBox
+import scala.tools.reflect.ToolBox
+
+scala> import scala.reflect.runtime.universe._
+import scala.reflect.runtime.universe._
+
+scala> object O { def apply() = 0 }
+defined module O
+
+scala> val ORef = reify { O }.tree
+ORef: reflect.runtime.universe.Tree = $read.O
+
+scala> val tree = Apply(Block(Nil, Block(Nil, ORef)), Nil)
+tree: reflect.runtime.universe.Apply = 
+{
+  {
+    $read.O
+  }
+}()
+
+scala> {val tb = reflect.runtime.currentMirror.mkToolBox(); tb.typeCheck(tree): Any}
+res0: Any = 
+{
+  {
+    $read.O.apply()
+  }
+}
+
+scala> 

test/files/run/t7185.scala

@@ -0,0 +1,12 @@
+import scala.tools.partest.ReplTest
+
+object Test extends ReplTest {
+  override def code = """
+import scala.tools.reflect.ToolBox
+import scala.reflect.runtime.universe._
+object O { def apply() = 0 }
+val ORef = reify { O }.tree
+val tree = Apply(Block(Nil, Block(Nil, ORef)), Nil)
+{val tb = reflect.runtime.currentMirror.mkToolBox(); tb.typeCheck(tree): Any}
+"""
+}