I don’t know if many of you use VS Code but the extension was very outdated.
I’ve made a pull request at the Stan VS Code Extension GitHub repository that was approved and the new version is now available in VS Code Extension Marketplace.
I’ve inserted a lot of knew functions and language features to make it uptodate with Stan version 2.26. (I might have missed some functionalities).
If you use VS Code try it out and, if you can, please contribute with better functionality and syntax highlighting.
Here is the full details on the new features and fixes:
Changes
 QR decomposition
 Added
qr_Q
andqr_R
to deprecated functions.  added
qr_thin_Q
andqr_thin_R
to functions.The functionsqr_thin_Q
andqr_thin_R
implement the thin QR decomposition, which is to be preferred to the fat QR decomposition that would be obtained by usingqr_Q
andqr_R
, as the latter would more easily run out of memory … (Section 1.2 Stan’s User Guide)
 Added
 Moved functions to deprecated functions (Section 10 of Stan Function Reference)
integrate_ode_rk45
integrate_ode_bdf
integrate_ode_adams
 New unnormalized distributions (Stan v 2.25)
 Changed all
*_lpdf
to also accept the new*_lupdf
(unnormalized log PDF) –_l[u]?pdf
(Section of Discrete Distributions in Stan Functions Reference).  Changed all
*_lpmf
to also accept the new*_lupmf
(unnormalized log PDF) –_l[u]?pmf
(Section of Continuous Distributions in Stan Functions Reference).
 Changed all
 New functions

hmm_marginal
function (Stan v 2.24) 
reduce_sum
andreduce_sum_static
functions (Stan v 2.23) 
map_rect
function (Stan v 2.18) 
integrate_1d
function (Stan v 2.18) 
algebra_solver
andalgebra_solver_newton
functions (Stan v 2.24)

 New GLM more efficient distribution functions
 Added the new discrete distribution family
bernoulli_logit_glm
Section 12.3 Stan Functions Reference) –bernoulli_logit_glm
andbernoulli_logit_glm_l[u]?pmf
. 
 Added the new discrete distribution family
ordered_logistic_glm
Section 13.9 Stan Functions Reference) –ordered_logistic_glm
andordered_logistic_glm_l[u]?pmf
.
 Added the new discrete distribution family
 Added the new discrete distribution family
neg_binomial_2_log_glm
Section 14.4 Stan Functions Reference) –neg_binomial_2_log_glm
andneg_binomial_2_log_glm_l[u]?pmf
.  Added the new discrete distribution family
poisson_log_glm
Section 14.7 Stan Functions Reference) –poisson_log_glm_lupmf
andpoisson_log_glm_l[u]?pmf
.  Added the new continuous distribution family
normal_id_glm
(Section 16.2 Stan Functions Reference) –normal_id_glm
andnormal_id_glm_l[u]?pdf
.
 Added the new discrete distribution family
 New distributions

discrete_range
(Section 13.7 Stan Functions Reference) –discrete_range
and [discrete_range_cdfdiscrete_range_lccdfdiscrete_range_lcdfdiscrete_range_l[u]?pmfdiscrete_range_rng
] 
ordered_probit
(Section 13.10 Stan Functions Reference) –ordered_probit
and [ordered_probit_l[u]?pdfordered_probit_rng
] 
multinomial_logit
(Section 15.2 Stan Functions Reference) –multinomial_logit
and [multinomial_logit_l[u]?pdfmultinomial_logit_rng
] 
beta_proportion
(Section 19.2 Stan Functions Reference) –beta_proportion
and [beta_proportionbeta_proportion_lccdfbeta_proportion_lcdfbeta_proportion_l[u]?pdfbeta_proportion_rng
])
