Fix #8050: Make isInlineable force less

The isInleable test forced the inline body. This causes problem
if the inline body is currently typechecked.

Author: odersky

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

@@ -50,7 +50,7 @@ object Inliner {
 
   /** Should call to method `meth` be inlined in this context? */
   def isInlineable(meth: Symbol)(implicit ctx: Context): Boolean =
-    meth.is(Inline) && !ctx.inInlineMethod && !bodyToInline(meth).isEmpty
+    meth.is(Inline) && meth.hasAnnotation(defn.BodyAnnot) && !ctx.inInlineMethod
 
   /** Should call be inlined in this context? */
   def isInlineable(tree: Tree)(implicit ctx: Context): Boolean = tree match {

tests/neg/i8050.scala

@@ -0,0 +1,5 @@
+object stuff with
+  def exec(dir: Int) = ???
+
+extension on (a: Int) with
+  inline def exec: Unit = stuff.exec("aaa") // error