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Diffstat (limited to 'src/doc/rustc-dev-guide/src/ast-validation.md')
| -rw-r--r-- | src/doc/rustc-dev-guide/src/ast-validation.md | 36 |
1 files changed, 33 insertions, 3 deletions
diff --git a/src/doc/rustc-dev-guide/src/ast-validation.md b/src/doc/rustc-dev-guide/src/ast-validation.md index ff549ca62..f3ac35e8a 100644 --- a/src/doc/rustc-dev-guide/src/ast-validation.md +++ b/src/doc/rustc-dev-guide/src/ast-validation.md @@ -1,6 +1,36 @@ # AST Validation -AST validation is the process of checking various correctness properties about -the AST after macro expansion. +<!-- toc --> -**TODO**: write this chapter. [#656](https://github.com/rust-lang/rustc-dev-guide/issues/656) +## About + +_AST validation_ is a separate AST pass that visits each +item in the tree and performs simple checks. This pass +doesn't perform any complex analysis, type checking or +name resolution. + +Before performing any validation, the compiler first expands +the macros. Then this pass performs validations to check +that each AST item is in the correct state. And when this pass +is done, the compiler runs the crate resolution pass. + +## Validations + +Validations are defined in `AstValidator` type, which +itself is located in `rustc_ast_passes` crate. This +type implements various simple checks which emit errors +when certain language rules are broken. + +In addition, `AstValidator` implements `Visitor` trait +that defines how to visit AST items (which can be functions, +traits, enums, etc). + +For each item, visitor performs specific checks. For +example, when visiting a function declaration, +`AstValidator` checks that the function has: + +* no more than `u16::MAX` parameters; +* c-variadic functions are declared with at least one named argument; +* c-variadic argument goes the last in the declaration; +* documentation comments aren't applied to function parameters; +* and other validations. |