fix #22168, im*I+I should be shown as (1+1im)*I (#22169)

* fix #22168, `im*I+I` should be shown as `(1+1im)*I`

* add test for `show(UniformScaling)`

* check the number of terms in `show(::UniformScaling)`

* fix the misuse of `|`

base/linalg/uniformscaling.jl

@@ -31,7 +31,13 @@ eltype(::Type{UniformScaling{T}}) where {T} = T
 ndims(J::UniformScaling) = 2
 getindex(J::UniformScaling, i::Integer,j::Integer) = ifelse(i==j,J.λ,zero(J.λ))
 
-show(io::IO, J::UniformScaling) = print(io, "$(typeof(J))\n$(J.λ)*I")
+function show(io::IO, J::UniformScaling)
+    s = "$(J.λ)"
+    if ismatch(r"\w+\s*[\+\-]\s*\w+", s)
+        s = "($s)"
+    end
+    print(io, "$(typeof(J))\n$s*I")
+end
 copy(J::UniformScaling) = UniformScaling(J.λ)
 
 transpose(J::UniformScaling) = J

test/linalg/uniformscaling.jl

@@ -38,6 +38,7 @@ end
 end
 
 @test copy(UniformScaling(one(Float64))) == UniformScaling(one(Float64))
+@test sprint(show,UniformScaling(one(Complex128))) == "UniformScaling{Complex{Float64}}\n(1.0 + 0.0im)*I"
 @test sprint(show,UniformScaling(one(Float32))) == "UniformScaling{Float32}\n1.0*I"
 
 λ = complex(randn(),randn())