Minor tweaks to remove method ambiguities and argument ambiguities

These were harmless enough, but should satisfy the tests in Base.

Also remove a display_error() overload because (a) it's not designed to
be overridden, and (b) this override doesn't really have the intended
effect anyway in the latest version where the REPL uses exception stacks
more extensively.

src/parser_api.jl

@@ -20,9 +20,6 @@ function Base.showerror(io::IO, err::ParseError)
     show_diagnostics(io, err.diagnostics, err.source)
 end
 
-Base.display_error(io::IO, err::ParseError, bt) = Base.showerror(io, err, bt)
-
-
 """
     parse!(stream::ParseStream; rule=:all)
 

src/syntax_tree.jl

@@ -7,6 +7,14 @@ mutable struct TreeNode{NodeData}   # ? prevent others from using this with Node
     parent::Union{Nothing,TreeNode{NodeData}}
     children::Union{Nothing,Vector{TreeNode{NodeData}}}
     data::Union{Nothing,NodeData}
+
+    # Use this constructor rather than the automatically generated one to pass
+    # Test.detect_unbound_args() test in Base.
+    function TreeNode{NodeData}(parent::Union{Nothing,TreeNode{NodeData}},
+                                children::Union{Nothing,Vector{TreeNode{NodeData}}},
+                                data::Union{Nothing,NodeData}) where {NodeData}
+        new{NodeData}(parent, children, data)
+    end
 end
 
 # Implement "pass-through" semantics for field access: access fields of `data`

src/tokenize.jl

@@ -1,6 +1,6 @@
 module Tokenize
 
-export tokenize, untokenize, Tokens
+export tokenize, untokenize
 
 using ..JuliaSyntax: JuliaSyntax, Kind, @K_str, @KSet_str
 

test/utils.jl

@@ -15,3 +15,10 @@
     @test ps("XX", fgcolor=:red, bgcolor=:green, href="https://www.example.com") ==
         "\e]8;;https://www.example.com\e\\\e[31m\e[42mXX\e[0;0m\e]8;;\e\\"
 end
+
+@testset "ambiguities" begin
+    if VERSION >= v"1.8"
+        @test detect_ambiguities(JuliaSyntax) == []
+        @test detect_unbound_args(JuliaSyntax) == []
+    end
+end