To	From	Method
string of code	literal code	std::stringify!{}
string of code	syntax tree	!quote(#syntax_tree).to_string()
string of code	TokenStream	.to_string()
string of syntax	literal code	"format!(""{:?}"",parse2::<SynType>(quote! {...}).expect(...)"
string of syntax	syntax tree	"format!(""{:?}""),…), format!(""{:#?}""),…)"
string of tokens	literal code	"format!(""{:?}"",quote! {...})"
string of tokens	TokenStream	"format!(""{:?}""),…), format!(""{:#?}""),…)"
syn::Error	TokenStream	.to_compile_error() [see Rule #7]
syntax tree	literal code	parse_quote!(…)
syntax tree	proc_macro::TokenStream	"parse_macro_input!(…), parse"
syntax tree	string of code	parse_str(…)
syntax tree	TokenStream	"parse2::<SynType>(…), etc"
TokenStream	literal code	quote!(…)
TokenStream	string of code	parse_str(…)
TokenStream	syntrax tree	"quote!(#syntax_tree) or .to_token_stream(),"
TokenStream	TokenStream	".into(), ::from(...) [see Rule #1]"