Fix #4431: Disallow macro parameters that are inline functions

Author: nicolasstucki

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

@@ -604,6 +604,10 @@ class ReifyQuotes extends MacroTransformWithImplicits with InfoTransformer {
                   """.stripMargin, tree.rhs.pos)
                 EmptyTree
             }
+          case tree: ValDef if tree.symbol.is(Param | Inline) && tree.symbol.owner.is(Macro) &&
+              defn.isFunctionClass(tree.tpe.widen.typeSymbol) =>
+            ctx.error("Macro parameters of function type cannot be `inline`", tree.pos)
+            EmptyTree
           case _ =>
             markDef(tree)
             checkLevel(mapOverTree(enteredSyms))

tests/neg/i4431.scala

@@ -0,0 +1,4 @@
+
+object Foo {
+  inline def h(inline f: Int => String): String = ~ '(f(42)) // error
+}

tests/neg/i4433.scala

@@ -0,0 +1,7 @@
+
+object Foo {
+  inline def g(inline p: Int => Boolean): Boolean = ~{ // error
+    if(p(5)) '(true)
+    else '(false)
+  }
+}