Merge pull request #14203 from dotty-staging/fix-#14137

Add hint on -Xcheck-macro scope extrusion failure

Author: anatoliykmetyuk

compiler/src/scala/quoted/runtime/impl/ScopeException.scala

@@ -33,4 +33,9 @@ object ScopeException:
             |
             |Use stack:
             |${currentScope.stack.mkString("\t", "\n\t", "\n")}
+            |
+            |Hint: A common reason for this to happen is when a `def` that creates a `'{...}`
+            |      captures an outer instance of `Quotes`. If this `def` is called in a splice
+            |      it will not track the `Quotes` provided by that particular splice.
+            |      To fix it add a `given Quotes` to this `def`.
           """.stripMargin)

tests/neg-macros/i14137/Macro_1.scala

@@ -0,0 +1,23 @@
+package x
+
+import scala.quoted._
+
+object Macro:
+
+   inline def genOp(inline f:Int): Int = ${
+      genOpImpl('f)
+   }
+
+   def genOpImpl(f: Expr[Int])(using Quotes): Expr[Int] = {
+
+      def firstOp(): Expr[Int] =
+      '{
+        var x=1
+        ${secondOp('x,f)}
+      }
+
+      def secondOp(x:Expr[Int], y:Expr[Int]): Expr[Int] =
+         '{ $x + $y }
+
+      firstOp()
+   }

tests/neg-macros/i14137/Test_2.scala

@@ -0,0 +1,6 @@
+package x
+
+object Main:
+
+  def main(args: Array[String]):Unit =
+    Macro.genOp(10) // error

tests/pos-macros/i14137/Macro_1.scala

@@ -0,0 +1,23 @@
+package x
+
+import scala.quoted._
+
+object Macro:
+
+   inline def genOp(inline f:Int): Int = ${
+      genOpImpl('f)
+   }
+
+   def genOpImpl(f: Expr[Int])(using Quotes): Expr[Int] = {
+
+      def firstOp()(using Quotes): Expr[Int] =
+      '{
+        var x=1
+        ${secondOp('x,f)}
+      }
+
+      def secondOp(x:Expr[Int], y:Expr[Int])(using Quotes): Expr[Int] =
+         '{ $x + $y }
+
+      firstOp()
+   }

tests/pos-macros/i14137/Test_2.scala

@@ -0,0 +1,6 @@
+package x
+
+object Main:
+
+  def main(args: Array[String]):Unit =
+    Macro.genOp(10)