Is it wrong to have two statements inside an if on vimscript? - vim

Question

I recently decided to revamp my .vimrc.
As per instructions here, I added a small snippet in a file called ultisnips_tab_hack.vim, which is sourced in my .vimrc.
The last line of that snippet is this:
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>"
Which from what I could tell was mapping Enter to an expression that would test if the pop-up menu was visible. If it was, the inserted text would be decided by the ExpandSnippetOrCarriageReturn() function that is defined in the snippet. Else a simple carriage return would be inserted.
This snippet is supposed to make YouCompleteMe and Ultisnips behave, and, as per this other comment, the last line should be modified to the following to make it also behave with vim-endwise.
let g:endwise_no_mappings = 1
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>\<C-R>=EndwiseDiscretionary()\<CR>"
Which is the same except that if the pop-up menu is not visible, it will also call the vim-endwise function to decide if something else should be inserted. And also, the endwise mapping is disabled, so that it won't conflict with our custom mapping.
So, I was trying to make a solution that would work whether vim-endwise was loaded or not (because I wanted to load it only on ruby files). And what I tried was:
if exists("*EndwiseDiscretionary")
let g:endwise_no_mappings = 1
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>\<C-R>=EndwiseDiscretionary()\<CR>"
else
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>"
endif
To my surprise, that gave me the following weird error on vim when I pressed Enter (and vim-endwise was loaded).
E15: Invalid Expression: ExpandSnippetOrCarriageReturn()\
And also, the following text was inserted: pumvisible() ? " instead of a carriage return.
To my even-more-surprise, though, the following caused no errors at all, whether vim-endwise was loaded or not.
let g:endwise_no_mappings = 1
if exists("*EndwiseDiscretionary")
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>\<C-R>=EndwiseDiscretionary()\<CR>"
else
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>"
endif
I've been bitten by some weird vimscript stuff before, so I'm now wondering if two statements inside an if causes this kind of problems and I'm supposed to always extract them to a function.
Or maybe I need a special separator that I don't know of, or something like that. Maybe it's a problem with a variable assignment right above a mapping?
Can any vim guru please elucidate me?
TL;DR
Causes weird E15: Invalid Expression: ExpandSnippetOrCarriageReturn()\ error when I press Enter on insert mode:
if exists("*EndwiseDiscretionary")
let g:endwise_no_mappings = 1
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>\<C-R>=EndwiseDiscretionary()\<CR>"
else
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>"
endif
Work as intended:
let g:endwise_no_mappings = 1
if exists("*EndwiseDiscretionary")
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>\<C-R>=EndwiseDiscretionary()\<CR>"
else
inoremap <expr> <CR> pumvisible() ? "\<C-R>=ExpandSnippetOrCarriageReturn()\<CR>" : "\<CR>"
endif