Can't use an expression as a dict key?

[Akaricchi]

wtf = 'wtf'
wtf = { wtf : wtf }

I would expect this code to be equivalent to:

wtf = { 'wtf' : 'wtf' }

Instead, it raises a parsing error:

meson.build:67:8: ERROR: Key must be a string.
wtf = { wtf : wtf }

Seems like an unreasonable limitation?

[nirbheek]

This is a known limitation and it's documented too: Keys are required to be literal strings, values can be objects of any type.

IIRC this was done because it was easier to implement at the time. I'm sure we'd be happy to accept patches to enable any object to be inserted as a key since almost all objects are immutable in Meson anyway.

[xclaesse]

Already fixed by this PR,I think: #6166

[marc-h38]

Already fixed by this PR,I think: #6166

Almost, see PR #6279 above (tagging @scivision)

In the mean time and for people with meson_version <= 0.52, re-sharing a smart workaround @eli-schwartz shared on IRC:

str_keys = [['one', '1'], ['two', '2'], ['three', '3']]
foreach key in str_keys: do_things(key[0], key[1])

This is basically re-implementing a dict manually with a multidimensional list. A bit tedious, but nowhere near as tedious as "unrolling" the foreach loop and Duplicating and Diverging a large do_things.

[eli-schwartz]

Oh, cool, I can drop my multidimensional lists soon. \o/

[xclaesse]

oh wait, actually += operator got fixed, not normal assignation.

k = 'somekey'
d = {k:1}
message(d[k])

-> ERROR: Key somekey is not in dict

[xclaesse]

Ok, I did a real refactor of dict: #6281

There was too much code duplication for my taste, and I found a few inconsistencies like:

# This was not raising error
k = 'a'
d = {k:1, 'a':2}
# This was not allowed, as well as any function call that returns string
d = {'a' / 'b':1}

[scivision]

I believe #6281 fixed this issue