Backport "Extract semanticDB for lifted definitions" to 3.3 LTS

compiler/src/dotty/tools/dotc/semanticdb/ExtractSemanticDB.scala

@@ -286,6 +286,14 @@ object ExtractSemanticDB:
       || sym.owner == defn.OpsPackageClass
       || qualifier.exists(excludeQual)
 
+    /** This block is created by lifting i.e. EtaExpansion */
+    private def isProbablyLifted(block: Block)(using Context) =
+      def isSyntheticDef(t: Tree) =
+        t match
+          case t: (ValDef | DefDef) => t.symbol.isSyntheticWithIdent
+          case _ => false
+      block.stats.forall(isSyntheticDef)
+
     private def traverseAnnotsOfDefinition(sym: Symbol)(using Context): Unit =
       for annot <- sym.annotations do
         if annot.tree.span.exists
@@ -438,6 +446,12 @@ object ExtractSemanticDB:
               registerUseGuarded(None, sym, tree.span, tree.source)
             case _ => ()
 
+        // If tree is lifted, ignore Synthetic status on all the definitions and traverse all childrens
+        case tree: Block if isProbablyLifted(tree) =>
+          tree.stats.foreach:
+            case t: (ValDef | DefDef) if !excludeChildren(t.symbol) => traverseChildren(t)
+            case _ => ()
+          traverse(tree.expr)
 
         case _ =>
           traverseChildren(tree)

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

@@ -39,9 +39,6 @@ abstract class Lifter {
   /** The tree of a lifted definition */
   protected def liftedDef(sym: TermSymbol, rhs: Tree)(using Context): MemberDef = ValDef(sym, rhs)
 
-  /** Is lifting performed on erased terms? */
-  protected def isErased = false
-
   private def lift(defs: mutable.ListBuffer[Tree], expr: Tree, prefix: TermName = EmptyTermName)(using Context): Tree =
     if (noLift(expr)) expr
     else {
@@ -117,8 +114,7 @@ abstract class Lifter {
     case Apply(fn, args) =>
       val fn1 = liftApp(defs, fn)
       val args1 = liftArgs(defs, fn.tpe, args)
-      if isErased then untpd.cpy.Apply(tree)(fn1, args1).withType(tree.tpe) // application may be partial
-      else cpy.Apply(tree)(fn1, args1)
+      cpy.Apply(tree)(fn1, args1)
     case TypeApply(fn, targs) =>
       cpy.TypeApply(tree)(liftApp(defs, fn), targs)
     case Select(pre, name) if isPureRef(tree) =>
@@ -141,7 +137,7 @@ abstract class Lifter {
    *
    *  unless `pre` is idempotent.
    */
-  def liftNonIdempotentPrefix(defs: mutable.ListBuffer[Tree], tree: Tree)(using Context): Tree =
+  private def liftNonIdempotentPrefix(defs: mutable.ListBuffer[Tree], tree: Tree)(using Context): Tree =
     if (isIdempotentExpr(tree)) tree else lift(defs, tree)
 
   /** Lift prefix `pre` of an application `pre.f(...)` to
@@ -154,7 +150,7 @@ abstract class Lifter {
    *  Note that default arguments will refer to the prefix, we do not want
    *  to re-evaluate a complex expression each time we access a getter.
    */
-  def liftPrefix(defs: mutable.ListBuffer[Tree], tree: Tree)(using Context): Tree =
+  private def liftPrefix(defs: mutable.ListBuffer[Tree], tree: Tree)(using Context): Tree =
     tree match
       case tree: Literal => tree
       case tree: This => tree
@@ -218,9 +214,6 @@ object LiftCoverage extends LiftImpure {
   }
 }
 
-object LiftErased extends LiftComplex:
-  override def isErased = true
-
 /** Lift all impure or complex arguments to `def`s */
 object LiftToDefs extends LiftComplex {
   override def liftedFlags: FlagSet = Method

tests/semanticdb/expect/Synthetic.expect.scala

@@ -58,4 +58,13 @@ class Synthetic/*<-example::Synthetic#*/ {
       given Int/*->scala::Int#*/ = 1
       foo/*->example::Synthetic#Contexts.foo().*/(0)
   }
+
+  // Argument lifting
+  val _ =
+    def f/*<-local14*/(s/*<-local12*/: String/*->scala::Predef.String#*/)(i/*<-local13*/: Int/*->scala::Int#*/ = s/*->local12*/.length/*->java::lang::String#length().*/()) = i/*->local13*/ +/*->scala::Int#`+`(+4).*/ 1
+    def g/*<-local18*/(s/*<-local16*/: String/*->scala::Predef.String#*/, t/*<-local17*/: String/*->scala::Predef.String#*/) = s/*->local16*/ +/*->java::lang::String#`+`().*/ t/*->local17*/
+
+    def impure/*<-local20*/(s/*<-local19*/: String/*->scala::Predef.String#*/) = { ???/*->scala::Predef.`???`().*/; s/*->local19*/ }
+    val _ = f/*->local14*/(impure/*->local20*/(""))()
+    val _ = g/*->local18*/(t/*->local17*/ = impure/*->local20*/(""), s/*->local16*/ = "a")
 }

tests/semanticdb/expect/Synthetic.scala

@@ -58,4 +58,13 @@ class Synthetic {
       given Int = 1
       foo(0)
   }
+
+  // Argument lifting
+  val _ =
+    def f(s: String)(i: Int = s.length()) = i + 1
+    def g(s: String, t: String) = s + t
+
+    def impure(s: String) = { ???; s }
+    val _ = f(impure(""))()
+    val _ = g(t = impure(""), s = "a")
 }