Awesome explanation receives a null tree

[som-snytt]

Minimized code

$ dotc -explain baddot.scala
-- [E018] Syntax Error: baddot.scala:7:30 --------------------------------------
7 |  def g: Int = try 42 finally ;
  |                              ^
  |                              expression expected but ';' found

Explanation
===========
An expression cannot start with ';'.

-- [E129] Potential Issue Warning: baddot.scala:7:21 ---------------------------
7 |  def g: Int = try 42 finally ;
  |                     ^
  |A pure expression does nothing in statement position; you may be omitting necessary parentheses

Explanation
===========
The pure expression null doesn't have any side effect and its result is not assigned elsewhere.
It can be removed without changing the semantics of the program. This may indicate an error.

1 warning found
1 error found

Output

The pure expression null doesn't have any side effect

Expectation

Awesome error messages should be robust about inputs without any ceremony by the message writer.

[nicolasstucki]

The expression def g: Int = try 42 finally ; is parsed as def g: Int = try 42 finally null;. The following warning is consistent. We should probably parse it as def g: Int = try 42 finally ();

[som-snytt]

Wow I didn't expect that explanation! Thanks. That means the ambiguous caret is a problem.

I almost joked how the message sounds like it means null, and it did mean that! For some reason, I didn't bother -Xprint.

I noticed this because I started poking at how error messages work.