Deprecate conj(::Any), add real(::Missing) and imag(::Missing) (#26288)

Author: dlfivefifty

base/deprecated.jl

@@ -1488,6 +1488,9 @@ function assert(x)
     @assert x ""
 end
 
+# Issue #26248
+@deprecate conj(x) x
+
 # END 0.7 deprecations
 
 # BEGIN 1.0 deprecations

base/missing.jl

@@ -64,14 +64,14 @@ isless(::Any, ::Missing) = true
 
 # Unary operators/functions
 for f in (:(!), :(~), :(+), :(-), :(identity), :(zero), :(one), :(oneunit),
-          :(abs), :(abs2), :(sign),
+          :(abs), :(abs2), :(sign), :(real), :(imag),
           :(acos), :(acosh), :(asin), :(asinh), :(atan), :(atanh),
           :(sin), :(sinh), :(cos), :(cosh), :(tan), :(tanh),
           :(exp), :(exp2), :(expm1), :(log), :(log10), :(log1p),
           :(log2), :(Math.exponent), :(sqrt), :(Math.gamma), :(Math.lgamma),
           :(iseven), :(ispow2), :(isfinite), :(isinf), :(isodd),
           :(isinteger), :(isreal), :(isnan), :(isempty),
-          :(iszero), :(transpose), :(adjoint), :(float))
+          :(iszero), :(transpose), :(adjoint), :(float), :(conj))
     @eval $(f)(::Missing) = missing
 end
 

base/operators.jl

@@ -733,8 +733,6 @@ See also: [`fld1`](@ref), [`mod1`](@ref).
 """
 fldmod1(x, y) = (fld1(x, y), mod1(x, y))
 
-conj(x) = x
-
 
 """
     widen(x)

stdlib/LinearAlgebra/test/generic.jl

@@ -335,6 +335,7 @@ Base.zero(::Type{ModInt{n}}) where {n} = ModInt{n}(0)
 Base.zero(::ModInt{n}) where {n} = ModInt{n}(0)
 Base.one(::Type{ModInt{n}}) where {n} = ModInt{n}(1)
 Base.one(::ModInt{n}) where {n} = ModInt{n}(1)
+Base.conj(a::ModInt{n}) where {n} = a
 Base.adjoint(a::ModInt{n}) where {n} = ModInt{n}(conj(a))
 Base.transpose(a::ModInt{n}) where {n} = a  # see Issue 20978
 LinearAlgebra.Adjoint(a::ModInt{n}) where {n} = adjoint(a)

test/missing.jl

@@ -142,7 +142,7 @@ Base.zero(::Type{Unit}) = Unit(0)
 Base.one(::Type{Unit}) = 1
 
 @testset "elementary functions" begin
-    elementary_functions = [abs, abs2, sign,
+    elementary_functions = [abs, abs2, sign, real, imag,
                             acos, acosh, asin, asinh, atan, atanh, sin, sinh,
                             conj, cos, cosh, tan, tanh,
                             exp, exp2, expm1, log, log10, log1p, log2,