rustc_ast/
mut_visit.rs

1//! A `MutVisitor` represents an AST modification; it accepts an AST piece and
2//! mutates it in place. So, for instance, macro expansion is a `MutVisitor`
3//! that walks over an AST and modifies it.
4//!
5//! Note: using a `MutVisitor` (other than the `MacroExpander` `MutVisitor`) on
6//! an AST before macro expansion is probably a bad idea. For instance,
7//! a `MutVisitor` renaming item names in a module will miss all of those
8//! that are created by the expansion of a macro.
9
10use std::ops::DerefMut;
11use std::panic;
12
13use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
14use rustc_span::source_map::Spanned;
15use rustc_span::{Ident, Span};
16use smallvec::{SmallVec, smallvec};
17use thin_vec::ThinVec;
18
19use crate::ast::*;
20use crate::ptr::P;
21use crate::tokenstream::*;
22use crate::visit::{AssocCtxt, BoundKind, FnCtxt, VisitorResult, try_visit, visit_opt, walk_list};
23
24mod sealed {
25    use rustc_ast_ir::visit::VisitorResult;
26
27    /// This is for compatibility with the regular `Visitor`.
28    pub trait MutVisitorResult {
29        type Result: VisitorResult;
30    }
31
32    impl<T> MutVisitorResult for T {
33        type Result = ();
34    }
35}
36
37use sealed::MutVisitorResult;
38
39super::common_visitor_and_walkers!((mut) MutVisitor);
40
41macro_rules! generate_flat_map_visitor_fns {
42    ($($name:ident, $Ty:ty, $flat_map_fn:ident$(, $param:ident: $ParamTy:ty)*;)+) => {
43        $(
44            fn $name<V: MutVisitor>(
45                vis: &mut V,
46                values: &mut ThinVec<$Ty>,
47                $(
48                    $param: $ParamTy,
49                )*
50            ) {
51                values.flat_map_in_place(|value| vis.$flat_map_fn(value$(,$param)*));
52            }
53        )+
54    }
55}
56
57generate_flat_map_visitor_fns! {
58    visit_items, P<Item>, flat_map_item;
59    visit_foreign_items, P<ForeignItem>, flat_map_foreign_item;
60    visit_generic_params, GenericParam, flat_map_generic_param;
61    visit_stmts, Stmt, flat_map_stmt;
62    visit_exprs, P<Expr>, filter_map_expr;
63    visit_expr_fields, ExprField, flat_map_expr_field;
64    visit_pat_fields, PatField, flat_map_pat_field;
65    visit_variants, Variant, flat_map_variant;
66    visit_assoc_items, P<AssocItem>, flat_map_assoc_item, ctxt: AssocCtxt;
67    visit_where_predicates, WherePredicate, flat_map_where_predicate;
68    visit_params, Param, flat_map_param;
69    visit_field_defs, FieldDef, flat_map_field_def;
70    visit_arms, Arm, flat_map_arm;
71}
72
73pub fn walk_flat_map_pat_field<T: MutVisitor>(
74    vis: &mut T,
75    mut fp: PatField,
76) -> SmallVec<[PatField; 1]> {
77    vis.visit_pat_field(&mut fp);
78    smallvec![fp]
79}
80
81fn visit_nested_use_tree<V: MutVisitor>(
82    vis: &mut V,
83    nested_tree: &mut UseTree,
84    nested_id: &mut NodeId,
85) {
86    vis.visit_id(nested_id);
87    vis.visit_use_tree(nested_tree);
88}
89
90macro_rules! generate_walk_flat_map_fns {
91    ($($fn_name:ident($Ty:ty$(,$extra_name:ident: $ExtraTy:ty)*) => $visit_fn_name:ident;)+) => {$(
92        pub fn $fn_name<V: MutVisitor>(vis: &mut V, mut value: $Ty$(,$extra_name: $ExtraTy)*) -> SmallVec<[$Ty; 1]> {
93            vis.$visit_fn_name(&mut value$(,$extra_name)*);
94            smallvec![value]
95        }
96    )+};
97}
98
99generate_walk_flat_map_fns! {
100    walk_flat_map_arm(Arm) => visit_arm;
101    walk_flat_map_variant(Variant) => visit_variant;
102    walk_flat_map_param(Param) => visit_param;
103    walk_flat_map_generic_param(GenericParam) => visit_generic_param;
104    walk_flat_map_where_predicate(WherePredicate) => visit_where_predicate;
105    walk_flat_map_field_def(FieldDef) => visit_field_def;
106    walk_flat_map_expr_field(ExprField) => visit_expr_field;
107    walk_flat_map_item(P<Item>) => visit_item;
108    walk_flat_map_foreign_item(P<ForeignItem>) => visit_foreign_item;
109    walk_flat_map_assoc_item(P<AssocItem>, ctxt: AssocCtxt) => visit_assoc_item;
110}
111
112fn walk_ty_alias_where_clauses<T: MutVisitor>(vis: &mut T, tawcs: &mut TyAliasWhereClauses) {
113    let TyAliasWhereClauses { before, after, split: _ } = tawcs;
114    let TyAliasWhereClause { has_where_token: _, span: span_before } = before;
115    let TyAliasWhereClause { has_where_token: _, span: span_after } = after;
116    vis.visit_span(span_before);
117    vis.visit_span(span_after);
118}
119
120pub fn walk_filter_map_expr<T: MutVisitor>(vis: &mut T, mut e: P<Expr>) -> Option<P<Expr>> {
121    vis.visit_expr(&mut e);
122    Some(e)
123}
124
125pub fn walk_flat_map_stmt<T: MutVisitor>(
126    vis: &mut T,
127    Stmt { kind, span, mut id }: Stmt,
128) -> SmallVec<[Stmt; 1]> {
129    vis.visit_id(&mut id);
130    let mut stmts: SmallVec<[Stmt; 1]> = walk_flat_map_stmt_kind(vis, kind)
131        .into_iter()
132        .map(|kind| Stmt { id, kind, span })
133        .collect();
134    match &mut stmts[..] {
135        [] => {}
136        [stmt] => vis.visit_span(&mut stmt.span),
137        _ => panic!(
138            "cloning statement `NodeId`s is prohibited by default, \
139             the visitor should implement custom statement visiting"
140        ),
141    }
142    stmts
143}
144
145fn walk_flat_map_stmt_kind<T: MutVisitor>(vis: &mut T, kind: StmtKind) -> SmallVec<[StmtKind; 1]> {
146    match kind {
147        StmtKind::Let(mut local) => smallvec![StmtKind::Let({
148            vis.visit_local(&mut local);
149            local
150        })],
151        StmtKind::Item(item) => vis.flat_map_item(item).into_iter().map(StmtKind::Item).collect(),
152        StmtKind::Expr(expr) => vis.filter_map_expr(expr).into_iter().map(StmtKind::Expr).collect(),
153        StmtKind::Semi(expr) => vis.filter_map_expr(expr).into_iter().map(StmtKind::Semi).collect(),
154        StmtKind::Empty => smallvec![StmtKind::Empty],
155        StmtKind::MacCall(mut mac) => {
156            let MacCallStmt { mac: mac_, style: _, attrs, tokens: _ } = mac.deref_mut();
157            for attr in attrs {
158                vis.visit_attribute(attr);
159            }
160            vis.visit_mac_call(mac_);
161            smallvec![StmtKind::MacCall(mac)]
162        }
163    }
164}
rustc_ast/mut_visit.rs

rustc_ast/
mut_visit.rs
