Programmatically assign output Hold[...] produced by errors to a variable

Question

expr = Return[1, 2]

Return::nofunc: Function 2 not found enclosing Return[1,2]. >>

(*Hold[Return[1, 2]]*)

However, Hold[Return[1, 2]] is not assigned to expr.Why does this happen? I want to use some code to store the output into that variable, is it possible?

PS: Please don't manually copy/paste or use methods like read the output cells/notebook contents and its variation. I prefer dealing with the problem directly.

Answer 1

Expressions that simply evaluate with messages are not returned wrapped in Hold, and there is no problem assigning these to a Symbol:

expr = Map[1, 2, 3, 4];

?expr

Map::nonopt: Options expected (instead of 4) beyond position 3 in Map[1,2,3,4]. An option must be a rule or a list of rules. >>

Global`expr

expr = Map[1, 2, 3, 4]

Your use of Return however breaks the normal evaluation order much as Throw or Break would, so Set is never completed. This is really no different from wondering why Print does not print "foo" or "bar" in:

Print["foo", "bar", Return[1, 2]]

Return::nofunc: Function 2 not found enclosing Return[1,2]. >>

Hold[Return[1, 2]]

If you explain how this output is originating perhaps I can recommend a work-around.