[rustc.git] / src / doc / rustc-dev-guide / src / syntax-intro.md

# Syntax and the AST

Working directly with source code is very inconvenient and error-prone. Thus,
before we do anything else, we convert raw source code into an AST. It turns
out that doing even this involves a lot of work, including lexing, parsing,
macro expansion, name resolution, conditional compilation, feature-gate
checking, and validation of the AST. In this chapter, we take a look at all
of these steps.

Notably, there isn't always a clean ordering between these tasks. For example,
macro expansion relies on name resolution to resolve the names of macros and
imports. And parsing requires macro expansion, which in turn may require
parsing the output of the macro.
Commit	Line	Data
ba9703b0 XL	1	# Syntax and the AST
	2
	3	Working directly with source code is very inconvenient and error-prone. Thus,
	4	before we do anything else, we convert raw source code into an AST. It turns
	5	out that doing even this involves a lot of work, including lexing, parsing,
	6	macro expansion, name resolution, conditional compilation, feature-gate
	7	checking, and validation of the AST. In this chapter, we take a look at all
	8	of these steps.
6a06907d XL	9
	10	Notably, there isn't always a clean ordering between these tasks. For example,
	11	macro expansion relies on name resolution to resolve the names of macros and
	12	imports. And parsing requires macro expansion, which in turn may require
	13	parsing the output of the macro.