Fix documentation by adding ndims(::AbstractJuMPScalar) (#2608)

src/JuMP.jl

@@ -374,11 +374,11 @@ See also: [`backend`](@ref).
 This function is unsafe for two main reasons.
 
 First, the formulation and order of variables and constraints in the unsafe
-backend may be different to the variables and constraints in `model`. This 
-can happen because of bridges, or because the solver requires the variables or 
-constraints in a specific order. In addition, the variable or constraint index 
-returned by [`index`](@ref) at the JuMP level may be different to the index of 
-the corresponding variable or constraint in the `unsafe_backend`. There is no 
+backend may be different to the variables and constraints in `model`. This
+can happen because of bridges, or because the solver requires the variables or
+constraints in a specific order. In addition, the variable or constraint index
+returned by [`index`](@ref) at the JuMP level may be different to the index of
+the corresponding variable or constraint in the `unsafe_backend`. There is no
 solution to this. Use the alternative suggested below instead.
 
 Second, the `unsafe_backend` may be empty, or lack some modifications made to
@@ -1027,6 +1027,7 @@ work for JuMP types) and exploits the mutability of `AffExpr` and `QuadExpr`.
 """
 abstract type AbstractJuMPScalar <: _MA.AbstractMutable end
 Base.ndims(::Type{<:AbstractJuMPScalar}) = 0
+Base.ndims(::AbstractJuMPScalar) = 0
 
 # These are required to create symmetric containers of AbstractJuMPScalars.
 LinearAlgebra.symmetric_type(::Type{T}) where {T<:AbstractJuMPScalar} = T

src/quad_expr.jl

@@ -51,8 +51,6 @@ mutable struct GenericQuadExpr{CoefType,VarType} <: AbstractJuMPScalar
     terms::OrderedDict{UnorderedPair{VarType},CoefType}
 end
 
-Base.ndims(::GenericQuadExpr) = 0
-
 """
     GenericQuadExpr(
         aff::GenericAffExpr{V,K},