lang: Fix non-string key panics in map function

[alisdair]

The map function assumed that the key arguments were strings, and would panic if they were not.

After this commit, calling map(1, 2) will result in a map {"1" = 2}, and calling map(null, 1) will result in a syntax error.

$ terraform console
> map(1, 2)
{
  "1" = 2
}
> map(null, 1)

>
Error: Error in function call

  on <console-input> line 1:
  (source code not available)

Call to function "map" failed: argument 1 is a null key.

Fixes #23346, fixes #23043

[codecov]

Codecov Report

Merging #24277 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #24277      +/-   ##
==========================================
- Coverage   56.96%   56.95%   -0.02%     
==========================================
  Files         656      656              
  Lines       59223    59225       +2     
==========================================
- Hits        33737    33730       -7     
- Misses      22471    22483      +12     
+ Partials     3015     3012       -3

Impacted Files	Coverage Δ
lang/funcs/collection.go	77.43% <100%> (+0.17%)	⬆️
checkpoint.go	4.76% <0%> (-28.58%)	⬇️
states/statemgr/filesystem.go	55.64% <0%> (-0.84%)	⬇️
backend/remote/backend_common.go	55.63% <0%> (+0.7%)	⬆️
dag/marshal.go	53.4% <0%> (+1.13%)	⬆️
communicator/communicator.go	83.33% <0%> (+3.7%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0bd40fd...37006c5. Read the comment docs.

[apparentlymart]

Not super important here, but just wanted to point out that you can return the special error type ArgError from a function (e.g. using NewArgErrorf instead of Errorf here) to indicate that a specific argument is incorrect.

When using functions with HCL, HCL recognizes that error type and indicates the specific single argument as the problem, rather than the entire call.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.