Add single-term multiplication for AbstractQ on v1.10 and above (#52342)

Author: jishnub

src/abstractq.jl

@@ -157,6 +157,9 @@ qsize_check(Q::AbstractQ, P::AbstractQ) =
     size(Q, 2) == size(P, 1) ||
         throw(DimensionMismatch("second dimension of A, $(size(Q,2)), must coincide with first dimension of B, $(size(P,1))"))
 
+# mimic the AbstractArray fallback
+*(Q::AbstractQ{<:Number}) = Q
+
 (*)(Q::AbstractQ, J::UniformScaling) = Q*J.λ
 function (*)(Q::AbstractQ, b::Number)
     T = promote_type(eltype(Q), typeof(b))

test/abstractq.jl

@@ -34,6 +34,7 @@ n = 5
         T <: Complex && @test_throws ErrorException transpose(Q)
         @test convert(AbstractQ{complex(T)}, Q) isa MyQ{complex(T)}
         @test convert(AbstractQ{complex(T)}, Q') isa AdjointQ{<:complex(T),<:MyQ{complex(T)}}
+        @test *(Q) == Q
         @test Q*I ≈ Q.Q*I rtol=2eps(real(T))
         @test Q'*I ≈ Q.Q'*I rtol=2eps(real(T))
         @test I*Q ≈ Q.Q*I rtol=2eps(real(T))