Fix comparison with nothing to use checking identity by === or `!…

…==`. (#159)

src/YAML.jl

@@ -44,7 +44,7 @@ const _dicttype = Union{Type,Function}
 
 # add a dicttype-aware version of construct_mapping to the constructors
 function _patch_constructors(more_constructors::_constructor, dicttype::_dicttype)
-    if more_constructors == nothing
+    if more_constructors === nothing
         more_constructors = Dict{String,Function}()
     else
         more_constructors = copy(more_constructors) # do not change the outside world

src/composer.jl

@@ -14,7 +14,7 @@ struct ComposerError
 end
 
 function show(io::IO, error::ComposerError)
-    if error.context != nothing
+    if error.context !== nothing
         print(io, error.context, " at ", error.context_mark, ": ")
     end
     print(io, error.problem, " at ", error.problem_mark)

src/constructor.jl

@@ -15,7 +15,7 @@ struct ConstructorError
 end
 
 function show(io::IO, error::ConstructorError)
-    if error.context != nothing
+    if error.context !== nothing
         print(io, error.context, " at ", error.context_mark, ": ")
     end
     print(io, error.problem, " at ", error.problem_mark)

src/parser.jl

@@ -17,7 +17,7 @@ struct ParserError
 end
 
 function show(io::IO, error::ParserError)
-    if error.context != nothing
+    if error.context !== nothing
         print(io, error.context, " at ", error.context_mark, ": ")
     end
     print(io, error.problem, " at ", error.problem_mark)
@@ -246,9 +246,9 @@ end
 function __parse_node(token::ScalarToken, stream::EventStream, block, start_mark, end_mark, anchor, tag, implicit)
     forward!(stream.input)
     end_mark = token.span.end_mark
-    if (token.plain && tag == nothing) || tag == "!"
+    if (token.plain && tag === nothing) || tag == "!"
         implicit = true, false
-    elseif tag == nothing
+    elseif tag === nothing
         implicit = false, true
     else
         implicit = false, false
@@ -345,7 +345,7 @@ function _parse_node(token, stream::EventStream, block, indentless_sequence)
     end
 
     token = peek(stream.input)
-    if start_mark == nothing
+    if start_mark === nothing
         start_mark = end_mark = token.span.start_mark
     end