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Error says none for overloaded symbol #22671

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som-snytt opened this issue Feb 26, 2025 · 5 comments · May be fixed by #22823 or #22869
Open

Error says none for overloaded symbol #22671

som-snytt opened this issue Feb 26, 2025 · 5 comments · May be fixed by #22823 or #22869
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better-errors Issues concerned with improving confusing/unhelpful diagnostic messages itype:bug Spree Suitable for a future Spree

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@som-snytt
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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.
@som-snytt som-snytt added itype:bug stat:needs triage Every issue needs to have an "area" and "itype" label better-errors Issues concerned with improving confusing/unhelpful diagnostic messages and removed stat:needs triage Every issue needs to have an "area" and "itype" label labels Feb 26, 2025
@som-snytt som-snytt mentioned this issue Feb 26, 2025
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@hamzaremmal hamzaremmal added the Spree Suitable for a future Spree label Mar 3, 2025
@mbovel
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mbovel commented Mar 17, 2025

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
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mbovel commented Mar 17, 2025

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 SethTisue mentioned this issue Mar 17, 2025
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@SethTisue
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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
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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

@jan-pieter jan-pieter linked a pull request Mar 17, 2025 that will close this issue
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@SethTisue
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(let's use the PR for any further discussion of implementation details)

@som-snytt som-snytt linked a pull request Mar 25, 2025 that will close this issue
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