Thanks for the tip ... but, after being stumped for a sec, I found it's actually Filter > Distortion > Lens Correction
There's another option which you might find more flexible.
Select the 'Rectangular Marquee Tool' (the one with the dotted line).
Use it to select all or part of your image.
Right-click over the selected part of the image and choose 'Free Transform' from the drop-down menu. This option allows you to stretch or compress the image to your heart's content. However, if you want to avoid cropping when stretching, you should enlarge the canvas first.
For more options in 'Free Transform' mode, right-click again and the drop-down menu will offer you, Warp, Perspective, Distort, Skew etc.
Experiment and see what works best. For example, the 'perspective' option allows you to make equal corrections on both side of the image simultaneously, when you tug on one of the little squares in the corner of the selection, whereas 'distort' allows you to make corrections that apply separately to one side of the image.
Wonderful thing, Photoshop.
I would add, for a really wide effect in confined environments containing close subjects, the TS-E lenses are the best option, especially the new TS-E 17mm. On full frame this lens provides a significantly wider effect than a single shot from a 14mm lens, when stitching the usual 3 images you get from one extreme of shift to the other.
On a cropped format, the 17mm TS-E, after stitching, will give you a wider result than a single shot from an EF-S 10mm lens, and superb detail and resolution from corner to corner.
If the subject is distant, there's usually no problem getting a perfect stitch. You can use any lens. You often don't even need a tripod.
If the subject is close, there can be huge problems with discontinuities and getting straight lines to match, but not if you use a TS-E.
With Photoshop's 'Photomerge' you can even get perfect stitches of close subjects using a TS-E lens without tripod.