feat: support getname for symbolic complex numbers

Author: AayushSabharwal

src/complex.jl

@@ -81,3 +81,20 @@ Base.iszero(x::Complex{<:Num}) = iszero(real(x)) && iszero(imag(x))
 Base.isone(x::Complex{<:Num}) = isone(real(x)) && iszero(imag(x))
 _iszero(x::Complex{<:Num}) = _iszero(unwrap(x))
 _isone(x::Complex{<:Num}) = _isone(unwrap(x))
+
+function SymbolicIndexingInterface.hasname(x::ComplexTerm)
+    a = arguments(unwrap(x.im))[1]
+    b = arguments(unwrap(x.re))[1]
+    return isequal(a, b) && hasname(a)
+end
+
+function _getname(x::ComplexTerm, val)
+    a = arguments(unwrap(x.im))[1]
+    b = arguments(unwrap(x.re))[1]
+    if isequal(a, b)
+        return _getname(a, val)
+    end
+    if val == _fail
+        throw(ArgumentError("Variable $x doesn't have a name."))
+    end
+end

src/variable.jl

@@ -503,13 +503,18 @@ function SymbolicIndexingInterface.symbolic_type(::Type{T}) where {S <: Abstract
     ArraySymbolic()
 end
 
-SymbolicIndexingInterface.hasname(x::Union{Num,Arr}) = hasname(unwrap(x))
+SymbolicIndexingInterface.hasname(x::Union{Num,Arr,Complex{Num}}) = hasname(unwrap(x))
 
 function SymbolicIndexingInterface.hasname(x::Symbolic)
     issym(x) || !iscall(x) || iscall(x) && (issym(operation(x)) || operation(x) == getindex)
 end
 
-SymbolicIndexingInterface.getname(x, val=_fail) = _getname(unwrap(x), val)
+# This is type piracy, but changing it breaks precompilation for MTK because it relies on this falling back to
+# `_getname` which calls `nameof` which returns the name of the system, when `x::AbstractSystem`.
+# FIXME: In a breaking release
+function SymbolicIndexingInterface.getname(x, val = _fail)
+    _getname(unwrap(x), val)
+end
 
 function SymbolicIndexingInterface.symbolic_evaluate(ex::Union{Num, Arr, Symbolic, Equation, Inequality}, d::Dict; kwargs...)
     val = fixpoint_sub(ex, d; kwargs...)

test/complex.jl

@@ -1,6 +1,7 @@
 using Symbolics, Test
 using SymbolicUtils: metadata
 using Symbolics: unwrap
+using SymbolicIndexingInterface: getname, hasname
 
 @variables a b::Real z::Complex (Z::Complex)[1:10]
 
@@ -37,3 +38,15 @@ end
     z2 = 1.0 + z*im
     @test isnothing(metadata(unwrap(z1.re)))
 end
+
+@testset "getname" begin
+    @variables t a b x::Complex y(t)::Complex z(a, b)::Complex
+    @test hasname(x)
+    @test getname(x) == :x
+    @test hasname(y)
+    @test getname(y) == :y
+    @test hasname(z)
+    @test getname(z) == :z
+    @test !hasname(2x)
+    @test !hasname(x + y)
+end