fix #36108, printing invalid numeric juxtapositions (#36122)

Author: JeffBezanson

base/show.jl

@@ -1342,7 +1342,8 @@ function show_unquoted(io::IO, ex::Expr, indent::Int, prec::Int, quote_level::In
 
         # scalar multiplication (i.e. "100x")
         elseif (func === :* &&
-            length(func_args)==2 && isa(func_args[1], Real) && isa(func_args[2], Symbol))
+            length(func_args) == 2 && isa(func_args[1], Union{Int, Int64, Float32, Float64}) &&
+            isa(func_args[2], Symbol) && !in(string(func_args[2])[1], ('e', 'E', 'f')))
             if func_prec <= prec
                 show_enclosed_list(io, '(', func_args, "", ')', indent, func_prec, quote_level)
             else

test/show.jl

@@ -138,6 +138,10 @@ end
 # basic expressions
 @test_repr "x + y"
 @test_repr "2e"
+@test_repr "2*e1"
+@test_repr "2*E1"
+@test_repr "2*f1"
+@test_repr "0x00*a"
 @test_repr "!x"
 @test_repr "f(1, 2, 3)"
 @test_repr "x = ~y"