Allow inlining of deferred defs

Author: timotheeandres

compiler/src/dotty/tools/dotc/inlines/Inlines.scala

@@ -565,9 +565,12 @@ object Inlines:
     private def inlinedTypeDef(tdef: TypeDef, inlinedSym: Symbol)(using Context): TypeDef =
       tpd.TypeDef(inlinedSym.asType).withSpan(parent.span)
 
-    private def inlinedRhs(rhs: Tree): Inlined =
-      val inlinedRhs = inlined(rhs)._2
-      Inlined(tpd.ref(parentSym), Nil, inlinedRhs).withSpan(parent.span)
+    private def inlinedRhs(rhs: Tree): Tree =
+      if rhs.isEmpty then
+        rhs
+      else
+        val inlinedRhs = inlined(rhs)._2
+        Inlined(tpd.ref(parentSym), Nil, inlinedRhs).withSpan(parent.span)
 
   end InlineParentTrait
 end Inlines

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

@@ -111,7 +111,6 @@ object Typer {
 
   def isInlineableFromInlineTrait(inlinedTraitSym: ClassSymbol, member: tpd.Tree)(using Context): Boolean =
     !(member.isInstanceOf[tpd.TypeDef] && inlinedTraitSym.typeParams.contains(member.symbol))
-    && !member.symbol.is(Deferred)
     && !member.symbol.isAllOf(Inline)
 }
 /** Typecheck trees, the main entry point is `typed`.

tests/pos/inline-trait-body-abstract-def.scala

@@ -1,6 +1,6 @@
-inline trait A:
-  def x: Int
+inline trait A[T]:
+  def x: T
 
-class B extends A:
-  override def x: Int = 1
-  def f = x
+class B extends A[Int]:
+  def x = 1
+  def f: Int = x