add errorshow for DimensionMismatch (#44121)

Close #44117

Author: Moelf

base/docs/basedocs.jl

@@ -365,7 +365,7 @@ julia> push!(a, 2, 3)
 Assigning `[]` does not eliminate elements from a collection; instead use [`filter!`](@ref).
 ```jldoctest
 julia> a = collect(1:3); a[a .<= 1] = []
-ERROR: DimensionMismatch("tried to assign 0 elements to 1 destinations")
+ERROR: DimensionMismatch: tried to assign 0 elements to 1 destinations
 [...]
 
 julia> filter!(x -> x > 1, a) # in-place & thus more efficient than a = a[a .> 1]

base/errorshow.jl

@@ -152,6 +152,7 @@ showerror(io::IO, ex::KeyError) = (print(io, "KeyError: key ");
                                    print(io, " not found"))
 showerror(io::IO, ex::InterruptException) = print(io, "InterruptException:")
 showerror(io::IO, ex::ArgumentError) = print(io, "ArgumentError: ", ex.msg)
+showerror(io::IO, ex::DimensionMismatch) = print(io, "DimensionMismatch: ", ex.msg)
 showerror(io::IO, ex::AssertionError) = print(io, "AssertionError: ", ex.msg)
 showerror(io::IO, ex::OverflowError) = print(io, "OverflowError: ", ex.msg)
 

stdlib/LinearAlgebra/docs/src/index.md

@@ -266,7 +266,7 @@ julia> b = [1 2 3; 4 5 6]
  4  5  6
 
 julia> b - U
-ERROR: DimensionMismatch("matrix is not square: dimensions are (2, 3)")
+ERROR: DimensionMismatch: matrix is not square: dimensions are (2, 3)
 Stacktrace:
 [...]
 ```