Handle suspension due to macro call completed in arbitrary phases

Previously we only supported suspension in Typer and Inliner. In the added test
case this happens in PostTyper, but I've seen it happen in Mixin too.

Fixes #18517.

Author: smarter

compiler/src/dotty/tools/dotc/core/Phases.scala

@@ -378,14 +378,18 @@ object Phases {
               ()
             else
               run
-          catch case ex: Throwable if !ctx.run.enrichedErrorMessage =>
-            println(ctx.run.enrichErrorMessage(s"unhandled exception while running $phaseName on $unit"))
-            throw ex
+            buf += unitCtx.compilationUnit
+          catch
+            case _: CompilationUnit.SuspendException => // this unit will be run again in `Run#compileSuspendedUnits`
+            case ex: Throwable if !ctx.run.enrichedErrorMessage =>
+              println(ctx.run.enrichErrorMessage(s"unhandled exception while running $phaseName on $unit"))
+              throw ex
           finally ctx.run.advanceUnit()
-          buf += unitCtx.compilationUnit
         end if
       end for
-      buf.result()
+      val res = buf.result()
+      ctx.run.nn.checkSuspendedUnits(res)
+      res
     end runOn
 
     /** Convert a compilation unit's tree to a string; can be overridden */

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

@@ -36,13 +36,7 @@ class Inlining extends MacroTransform, IdentityDenotTransformer {
 
   override def run(using Context): Unit =
     if ctx.compilationUnit.needsInlining || ctx.compilationUnit.hasMacroAnnotations then
-      try super.run
-      catch case _: CompilationUnit.SuspendException => ()
-
-  override def runOn(units: List[CompilationUnit])(using Context): List[CompilationUnit] =
-    val newUnits = super.runOn(units).filterNot(_.suspended)
-    ctx.run.nn.checkSuspendedUnits(newUnits)
-    newUnits
+      super.run
 
   override def checkPostCondition(tree: Tree)(using Context): Unit =
     tree match {

tests/pos-macros/i18517/Caller.scala

@@ -0,0 +1,17 @@
+package dummy
+
+trait BG {
+  val   description: { type Structure }
+  type  Structure =  description.Structure
+}
+
+abstract class Caller extends BG {
+  type Foo >: this.type <: this.type
+
+  transparent inline def generate2() =
+    ${Macro.impl() }
+
+  final val description = {
+    generate2()
+  }
+}

tests/pos-macros/i18517/Macro.scala

@@ -0,0 +1,7 @@
+package dummy
+
+import scala.quoted.*
+
+object Macro:
+  def impl()(using quotes:Quotes) : Expr[Any] =
+    '{ null }

tests/pos-macros/i18517/User.scala

@@ -0,0 +1,6 @@
+package dummy
+
+trait User:
+  final def bar(cell:Any) : Unit =
+    (cell: cell.type) match
+      case c: (Caller & cell.type) => ()