Test method ambiguity

test/detect_ambiguities.jl

@@ -0,0 +1,22 @@
+using Test
+
+_deps = quote
+    SparseArrays
+    LinearAlgebra
+    FillArrays
+    SIMD
+end
+deps = [x for x in _deps.args if x isa Symbol]
+@debug "Loading dependencies:" deps
+for m in deps
+    @eval using $m
+end
+
+modules = eval.(deps)
+ambiguities = detect_ambiguities(modules..., imported=true, recursive=true)
+if !isempty(ambiguities)
+    @error "Ambiguities found in dependencies." deps ambiguities
+else
+    using SparseXX
+    @test detect_ambiguities(SparseXX, imported=true, recursive=true) == []
+end

test/test_ambiguity.jl

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+module TestAmbiguity
+using Test
+
+@testset "method ambiguity" begin
+    # Ambiguity test is run inside a clean process.
+    # https://github.com/JuliaLang/julia/issues/28804
+    script = joinpath(@__DIR__, "detect_ambiguities.jl")
+    code = """
+    $(Base.load_path_setup_code())
+    include($(repr(script)))
+    """
+    cmd = Base.julia_cmd()
+    if Base.JLOptions().color == 1
+        cmd = `$cmd --color=yes`
+    end
+    cmd = `$cmd --startup-file=no -e $code`
+    @test success(pipeline(cmd; stdout=stdout, stderr=stderr))
+end
+
+end  # module