Add dirichlet/multi_normal lpxf_expr, fix string interpolation in print

- Add dirichlet_lpdf, multi_normal_lpdf to lpxf_expr list
- Add dirichlet_lpdfs to builtin
- Replace string interpolation in print calls with separate arguments

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: nsiccha

src/StanBlocks.jl

@@ -47,15 +47,15 @@ unwrap_error(e) = e
 
 function _format_cause(phase, context, cause_error, expr_stack)
     sprint() do io
-        print(io, "StanBlocksError [$(phase)]: $(context)\n")
+        print(io, "StanBlocksError [", phase, "]: ", context, "\n")
         print(io, "  Caused by: ")
         showerror(io, cause_error)
         if !isempty(expr_stack)
             println(io, "\n\n  While processing:")
             for (i, item) in enumerate(reverse(expr_stack))
                 x, lnn = item isa Tuple ? item : (item, nothing)
-                loc = lnn isa LineNumberNode ? " at $(lnn.file):$(lnn.line)" : ""
-                println(io, "   [$i] $x$loc")
+                loc = lnn isa LineNumberNode ? (" at ", lnn.file, ":", lnn.line) : ()
+                print(io, "   [", i, "] ", x, loc..., "\n")
             end
         end
     end
@@ -72,7 +72,7 @@ function Base.showerror(io::IO, e::StanBlocksError, bt; kwargs...)
     try
         showerror(io, e)
     catch internal_err
-        print(io, "StanBlocksError [$(e.phase)]: $(e.context)")
+        print(io, "StanBlocksError [", e.phase, "]: ", e.context)
         print(io, "\n  (internal error in showerror: ")
         showerror(io, internal_err)
         print(io, ")")

src/slic_stan/builtin.jl

@@ -333,6 +333,7 @@ import Statistics
     normal_lpdfs(args...) = normal_lpdf(args...)
     normal_lpdfs(obs::anything[n], loc, scale) = jbroadcasted(normal_lpdfs, obs, loc, scale)
     multi_normal_lpdfs(args...) = multi_normal_lpdf(args...)
+    dirichlet_lpdfs(args...) = dirichlet_lpdf(args...)
     # Scalar-fallback _lpdfs for distributions missing vectorized forms.
     # The args... variant handles scalar obs; array broadcasting is left for future work.
     cauchy_lpdfs(args...) = cauchy_lpdf(args...)

src/slic_stan/slic.jl

@@ -687,6 +687,7 @@ for lpxf_rhs in (
     :beta_lpdf, :lognormal_lpdf, :exponential_lpdf, :gamma_lpdf,
     :inv_gamma_lpdf, :weibull_lpdf, :uniform_lpdf,
     :double_exponential_lpdf, :logistic_lpdf,
+    :dirichlet_lpdf, :multi_normal_lpdf,
     :bernoulli_lpmf, :bernoulli_logit_lpmf, :binomial_lpmf, :binomial_logit_lpmf,
     :neg_binomial_2_lpmf, :poisson_lpmf, :poisson_log_lpmf,
 )
@@ -781,7 +782,7 @@ Base.show(io::IO, x::StanModel) = show(StanIO(io), x)
 Base.show(io::IO, x::SlicModel; mayfail=true) = try
     print(io, stan_model(x))
 catch e
-    mayfail && return print(io, "SlicModel: Something went wrong: $e")
+    mayfail && return print(io, "SlicModel: Something went wrong:", e)
     rethrow(e)
 end
 Base.show(io::IO, x::StanBlock) = if true#length(content(x)) > 0