Add noscope macro to make try blocks evaluate in the local scope

[IanButterworth]

It could be generally useful to evaluate a try in the local scope, as is the case in #39138

Based on a suggestion by @vtjnash this adds @noscope for making try blocks evaluate in the local scope

julia> x
ERROR: UndefVarError: x not defined

julia> try
            x = 1
            error()
        catch err
            display(err)
        finally
            println("finally")
        end
ErrorException()
finally

julia> x
ERROR: UndefVarError: x not defined

julia> @noscope try
            x = 1
            error()
        catch err
            display(err)
        finally
            println("finally")
        end
ErrorException()
finally

julia> x
1

If this is supported, there may be a better place for the code and tests to sit?

[fredrikekre]

Maybe

Suggested change

	macro noscope(ex)
	macro noscope360(ex)

?

[IanButterworth]

Actually, I think this and all the finally and catch blocks should still be scoped

Suggested change

	begin
	let

[f0103]

[JeffBezanson]

From triage:

• Basically yes
• Would be nice to implement it properly in the front-end, and handle all kinds of scope-introducing blocks
• We probably still want the variable in catch e to be local to its block. Similarly for @noscope let x = ..., the x should still be local, but nothing inside should introduce new variables to the scope. That will require some surgery in the scope pass.

[IanButterworth]

With #48434 being open and it being unlikely that I'd take this forward, I'll close this