Fix #5107: disallow block as Apply.fun

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -279,6 +279,7 @@ class TreeChecker extends Phase with SymTransformer {
         case _ if tree.isType =>
           promote(tree)
         case _ =>
+          checkApplyNonBlock(tree)
           val tree1 = super.typedUnadapted(tree, pt, locked)
           def isSubType(tp1: Type, tp2: Type) =
             (tp1 eq tp2) || // accept NoType / NoType
@@ -300,6 +301,12 @@ class TreeChecker extends Phase with SymTransformer {
       res
     }
 
+    def checkApplyNonBlock(tree: untpd.Tree)(implicit ctx: Context) = tree match {
+      case tree: untpd.Apply => assert(!tree.fun.isInstanceOf[untpd.Block])
+      case tree: untpd.UnApply => assert(!tree.fun.isInstanceOf[untpd.Block])
+      case _ =>
+    }
+
     def checkNotRepeated(tree: Tree)(implicit ctx: Context): tree.type = {
       def allowedRepeated = tree.tpe.widen.isRepeatedParam
 

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2378,7 +2378,12 @@ class Typer extends Namer
             }
           } else issueErrors()
         }
-        else readaptSimplified(tpd.Apply(tree, args))
+        else tree match {
+          case tree: Block =>
+            readaptSimplified(tpd.Block(tree.stats, tpd.Apply(tree.expr, args)))
+          case _ =>
+            readaptSimplified(tpd.Apply(tree, args))
+        }
       }
       addImplicitArgs(argCtx(tree))
     }

tests/pos/i5107.scala

@@ -0,0 +1,9 @@
+class Test {
+  inline def foo(x: Int = 5)(implicit y: Int): Int =
+    if (x > 0) y * y
+    else y + y
+
+  implicit val m: Int = 7
+
+  (new Test).foo()
+}