Fix the inference of the function coloring for static compilation

src/interface.jl

@@ -190,10 +190,12 @@ function coloring(
     A::AbstractMatrix,
     problem::ColoringProblem,
     algo::GreedyColoringAlgorithm;
-    decompression_eltype::Type{R}=Float64,
+    decompression_eltype::Type=Float64,
     symmetric_pattern::Bool=false,
-) where {R}
-    return _coloring(WithResult(), A, problem, algo, R, symmetric_pattern)
+)
+    return _coloring(
+        WithResult(), A, problem, algo, decompression_eltype, symmetric_pattern
+    )
 end
 
 """

test/runtests.jl

@@ -88,6 +88,9 @@ include("utils.jl")
                     include("type_stability.jl")
                 end
             end
+            @testset "Static compilation" begin
+                include("static_compilation.jl")
+            end
             @testset "Allocations" begin
                 include("allocations.jl")
             end

test/static_compilation.jl

@@ -0,0 +1,47 @@
+# Guard for static compilation (`juliac --trim=safe`).
+#
+# The C and Fortran interfaces compile SMC.jl into a standalone shared library.
+# The trimming verifier rejects any call whose result type is not fully inferred,
+# so `coloring` must return a concrete type.
+
+using SparseArrays
+using SparseMatrixColorings
+using Test
+
+const STATIC_COMBOS = [
+    (ColoringProblem{:nonsymmetric,:column}(), GreedyColoringAlgorithm{:direct}()),
+    (ColoringProblem{:nonsymmetric,:row}(), GreedyColoringAlgorithm{:direct}()),
+    (ColoringProblem{:symmetric,:column}(), GreedyColoringAlgorithm{:direct}()),
+    (ColoringProblem{:symmetric,:column}(), GreedyColoringAlgorithm{:substitution}()),
+    (ColoringProblem{:nonsymmetric,:bidirectional}(), GreedyColoringAlgorithm{:direct}()),
+    (
+        ColoringProblem{:nonsymmetric,:bidirectional}(),
+        GreedyColoringAlgorithm{:substitution}(),
+    ),
+]
+
+# Symmetric, so that it is a valid input for every combination above.
+const STATIC_MATRIX = sparse(
+    [1, 2, 1, 2, 3, 2, 3, 4, 3, 4], [1, 1, 2, 2, 2, 3, 3, 3, 4, 4], ones(10), 4, 4
+)
+
+@testset "coloring infers a concrete result type" begin
+    @testset "$(typeof(problem)) / $(typeof(algo))" for (problem, algo) in STATIC_COMBOS
+        for decompression_eltype in (Float32, Float64)
+            for symmetric_pattern in (false, true)
+                @test (@inferred(
+                    (
+                        (A, p, a, sp, R) ->
+                            coloring(A, p, a; decompression_eltype=R, symmetric_pattern=sp)
+                    )(
+                        STATIC_MATRIX,
+                        problem,
+                        algo,
+                        symmetric_pattern,
+                        decompression_eltype,
+                    )
+                )) isa AbstractColoringResult
+            end
+        end
+    end
+end