Partial fix for printing

Two things to fix:

- We do correct-but-ugly printing of `end` when it's inside another
     expression (probably due to setting beginsym to false too often)
- `show` doesn't play nicely with ternary expressions, which seems like an
     unrelated issue.

Author: mlechu

base/show.jl

@@ -2526,6 +2526,8 @@ function show_unquoted(io::IO, ex::Expr, indent::Int, prec::Int, quote_level::In
         # we want to show bad ASTs reasonably to make errors understandable.
         lambda_io = IOContext(io, :SOURCE_SLOTNAMES => false)
         show_unquoted_expr_fallback(lambda_io, ex, indent, quote_level)
+    elseif get(io, beginsym, false) && head in (:begin, :end)
+        print(io, head)
     else
         unhandled = true
     end

test/show.jl

@@ -2370,13 +2370,14 @@ end
 
 # begin/end indices
 @weak_test_repr "a[begin, end, (begin; end)]"
-@test_broken repr(Base.remove_linenums!(:(a[begin, end, (begin; end)]))) == ":(a[begin, end, (begin;\n          end)])"
+@test repr(Base.remove_linenums!(:(a[begin, end, (begin; end)]))) == ":(a[begin, end, (begin;\n          end)])"
 @weak_test_repr "a[begin, end, let x=1; (x+1;); end]"
-@test_broken repr(Base.remove_linenums!(:(a[begin, end, let x=1; (x+1;); end]))) ==
+@test repr(Base.remove_linenums!(:(a[begin, end, let x=1; (x+1;); end]))) ==
         ":(a[begin, end, let x = 1\n          begin\n              x + 1\n          end\n      end])"
 @test_repr "a[(bla;)]"
 @test_repr "a[(;;)]"
 @weak_test_repr "a[x -> f(x)]"
+@test_broken @weak_test_repr """:([1,2,3,4][:end === :end ? end : var"end"])"""
 
 @testset "Base.Iterators" begin
     @test sprint(show, enumerate("test")) == "enumerate(\"test\")"