Error says none for overloaded symbol

[som-snytt]

Compiler version

3.6.3

Minimized code

object X:
  def x: Int = 42
  def x(y: Int): Int = x + y

def test =
  X.x = 27

Output

➜  snips scala-cli compile --server=false -S 3.6.3 badass.scala
-- [E052] Type Error: /home/amarki/snips/badass.scala:7:6 ----------------------
7 |  X.x = 27
  |  ^^^^^^^^
  |  Reassignment to val <none>
  |
  | longer explanation available when compiling with `-explain`
1 error found
Compilation failed

Expectation

Tell me the name of the unassignable overload.

[mbovel]

This issue was picked for the Scala Issue Spree of today, Monday, March 17th. @SethTisue, @iusildra, @jan-pieter and @ajafri2001 will be working on it. If you have any insight into the issue or guidance on how to fix it, please leave it here.

[mbovel]

Using -Ydebug-error, we can find the origin of the error:

java.lang.Exception: Stack trace
        at java.base/java.lang.Thread.dumpStack(Thread.java:1389)
        at dotty.tools.dotc.report$.error(report.scala:70)
        at dotty.tools.dotc.typer.Typer.reassignmentToVal$1(Typer.scala:1392)
        at dotty.tools.dotc.typer.Typer.typedAssign(Typer.scala:1475)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3567)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3648)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3725)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3730)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3841)

scala3/compiler/src/dotty/tools/dotc/typer/Typer.scala

Line 1392 in 48a7c64

report.error(ReassignmentToVal(lhsCore.symbol.name), tree.srcPos)

Seems like the tree has no symbol there. Is this correct? If so, maybe a workaround to find the name can be used in this situation?

[SethTisue]

The lhsCore tree has no symbol because the compiler hasn't resolved the overload.

Can look at tree.lhs instead? The problem is that lhs might have different shapes; in this particular test case it's Select, but it might also be a plain Indent — and are there other possibilities?

[SethTisue]

after some fumbling we released that NameTree exists. I'm not sure if tree.lhs (or lhsCore) is actually guaranteed to be a NameTree, but if it is we can just call .name on it

[SethTisue]

(let's use the PR for any further discussion of implementation details)