Fix crash in Parser::parse_term()

[mmaxim]

Parser::parse_term uses dynamic_cast to attempt to see if the LHS of an expression can be treated as a String_Schema in order to check if string interpolation is in play. Unfortunately, it relies on dynamic_cast throwing an exception if the cast fails, which is not how C++11 behaves. An exception is only thrown from dynamic_cast when references are being cast, not pointers (since a reference cannot be null, but a pointer can):

http://stackoverflow.com/questions/16476613/when-dynamic-cast-will-throw-exception-in-case-used-with-pointer

The change in this pull request removes the try/catch construct, and replaces it with a simple check to see if the pointer is null or not.

[xzyfer]

Nice catch @mmaxim ! Was this code causing you actual issues? I ask because it'd be great to add a test spec that catches this crash.

[mmaxim]

Yeah this did cause a problem, which is how I stumbled upon it. It could mean there is a deeper bug int he parser to even get to that block of code in the first place, but I didn't look that hard (since this fix just made everything work for me). I'll work on getting a minimal test case.

[xzyfer]

Thanks for working on a test case. We really appreciate it.
On 22 Jan 2015 03:39, "Mike Maxim" notifications@github.com wrote:

Yeah this did cause a problem, which is how I stumbled upon it. It could
mean there is a deeper bug int he parser to even get to that block of code
in the first place, but I didn't look that hard (since this fix just made
everything work for me). I'll work on getting a minimal test case.

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#846 (comment).

[xzyfer]

@mgreter does this conflict with your work? If not lets get it shipped.

[mgreter]

LGTM!