[tex-k] \showthe followed with undefined control sequence misbehaves

[jfbu]

[Please CC if replying]

Hello,

Consider the following file

----
\showthe\foo
\let\foo\relax
\bye
----

Executing tex on it gives the following log file
(I hit <RETURN> at each prompt)

----
This is TeX, Version 3.141592653 (TeX Live 2024) (preloaded format=tex 2024.6.8)  18 JUL 2024 10:12
**testshowthe
(./testshowthe.tex
! Undefined control sequence.
l.1 \showthe\foo
                
? 
! You can't use `\let' after \the.
l.2 \let
        \foo\relax
? 
> 0.
l.2 \let
        \foo\relax
? 
! Undefined control sequence.
l.2 \let\foo
            \relax
? 
 )
No pages of output.
----

The "You can't use `\let' after \the" looks like unexpected behavior
to me.

On a more minor note, shouldn't it be "`\the'" not "\the" ;-) ?


For comparison

----
\showthe\let
\let\foo\relax
\show\foo
\bye
----

appears to produce somewhat more expected output.

----
! You can't use `\let' after \the.
l.1 \showthe\let
                
? 
> 0.
l.1 \showthe\let
                
? 
> \foo=\relax.
l.3 \show\foo
             
? 
 )
----


Best,

Jean-François Burnol