MethodError in qr() and pinv() for matrices with symbols

[dcabecinhas]

To reproduce

using ModelingToolkit
using LinearAlgebra
@variables A[1:2,1:2]

qr(A)
pinv(A)

I'm finding these as I'm replacing parameters for symbolic variables in my code.

julia> qr(A)
ERROR: MethodError: no method matching real(::Operation)
Closest candidates are:
  real(::Missing) at missing.jl:100
  real(::Complex) at complex.jl:63
  real(::Real) at complex.jl:77
  ...
Stacktrace:
 [1] reflector! at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.4/LinearAlgebra/src/generic.jl:1433 [inlined]
 [2] qrfactUnblocked!(::Array{Operation,2}) at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.4/LinearAlgebra/src/qr.jl:193
 [3] qr! at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.4/LinearAlgebra/src/qr.jl:295 [inlined]
 [4] qr! at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.4/LinearAlgebra/src/qr.jl:297 [inlined]
 [5] qr(::Array{Operation,2}; kwargs::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}) at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.4/LinearAlgebra/src/qr.jl:383
 [6] qr(::Array{Operation,2}) at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.4/LinearAlgebra/src/qr.jl:380
 [7] top-level scope at REPL[9]:1

> julia> pinv(A)
> ERROR: MethodError: no method matching AbstractFloat(::ModelingToolkit.Constant)
> Closest candidates are:
>   AbstractFloat(::T) where T<:Number at boot.jl:715
>   AbstractFloat(::Bool) at float.jl:258
>   AbstractFloat(::Int8) at float.jl:259
>   ...
> 

[ChrisRackauckas]

Symbolic pinv isn't possible because unpivoted svd isn't possible, and pivots cannot be done symbolically because they are norms of values. For qr, #465 fixes it