Improve error message for initial_params

src/sampler.jl

@@ -156,6 +156,17 @@
 """
 initialsampler(spl::Sampler) = SampleFromPrior()
 
+function set_values!!(
+    varinfo::AbstractVarInfo, initial_params::AbstractVector, spl::AbstractSampler
+)
+    throw(
+        ArgumentError(
+            "`initial_params` must be a vector of type `Union{Real,Missing}`. " *
+            "If `initial_params` is a vector of vectors, please flatten it (e.g. using `vcat`) first.",
+        ),
+    )
+end
+
 function set_values!!(
     varinfo::AbstractVarInfo,
     initial_params::AbstractVector{<:Union{Real,Missing}},
@@ -164,7 +175,8 @@
     flattened_param_vals = varinfo[spl]
     length(flattened_param_vals) == length(initial_params) || throw(
         DimensionMismatch(
-            "Provided initial value size ($(length(initial_params))) doesn't match the model size ($(length(flattened_param_vals)))",
+            "Provided initial value size ($(length(initial_params))) doesn't match " *
+            "the model size ($(length(flattened_param_vals))).",
         ),
     )
 
@@ -183,6 +195,24 @@
 function set_values!!(
     varinfo::AbstractVarInfo, initial_params::NamedTuple, spl::AbstractSampler
 )
+    vars_in_varinfo = keys(varinfo)
+    for v in keys(initial_params)
+        vn = VarName{v}()
+        if !(vn in vars_in_varinfo)
+            for vv in vars_in_varinfo
+                if subsumes(vn, vv)
+                    throw(
+                        ArgumentError(
+                            "The current model does not contain variable $v, but there's ($vv) in the model. " *
+                            "Using NamedTuple for initial_params is not supported for this model. " *
+                            "Please use AbstractVector for initial_params instead of NamedTuple.",
+                        ),
+                    )
+                end
+            end
+            throw(ArgumentError("Variable $v not found in the model."))
+        end
+    end
     initial_params = NamedTuple(k => v for (k, v) in pairs(initial_params) if v !== missing)
     return update_values!!(
         varinfo, initial_params, map(k -> VarName{k}(), keys(initial_params))

test/sampler.jl

@@ -178,5 +178,30 @@
                 @test c1[1].metadata.s.vals == c2[1].metadata.s.vals
             end
         end
+
+        @testset "error handling" begin
+            # https://github.com/TuringLang/Turing.jl/issues/2452
+            @model function constrained_uniform(n)
+                Z ~ Uniform(10, 20)
+                X = Vector{Float64}(undef, n)
+                for i in 1:n
+                    X[i] ~ Uniform(0, Z)
+                end
+            end
+
+            n = 2
+            initial_z = 15
+            initial_x = [0.2, 0.5]
+            model = constrained_uniform(n)
+            vi = VarInfo(model)
+
+            @test_throws ArgumentError DynamicPPL.initialize_parameters!!(
+                vi, [initial_z, initial_x], DynamicPPL.SampleFromPrior(), model
+            )
+
+            @test_throws ArgumentError DynamicPPL.initialize_parameters!!(
+                vi, (X=initial_x, Z=initial_z), DynamicPPL.SampleFromPrior(), model
+            )
+        end
     end
 end