bpo-42128: Structural Pattern Matching (PEP 634) (GH-22917)
Co-authored-by: Guido van Rossum <guido@python.org>
Co-authored-by: Talin <viridia@gmail.com>
Co-authored-by: Pablo Galindo <pablogsal@gmail.com>
diff --git a/Python/symtable.c b/Python/symtable.c
index cce1b1b..10a47d1 100644
--- a/Python/symtable.c
+++ b/Python/symtable.c
@@ -207,6 +207,7 @@ static int symtable_visit_argannotations(struct symtable *st, asdl_arg_seq *args
static int symtable_implicit_arg(struct symtable *st, int pos);
static int symtable_visit_annotations(struct symtable *st, arguments_ty, expr_ty);
static int symtable_visit_withitem(struct symtable *st, withitem_ty item);
+static int symtable_visit_match_case(struct symtable *st, match_case_ty m);
static identifier top = NULL, lambda = NULL, genexpr = NULL,
@@ -239,6 +240,7 @@ symtable_new(void)
goto fail;
st->st_cur = NULL;
st->st_private = NULL;
+ st->in_pattern = 0;
return st;
fail:
PySymtable_Free(st);
@@ -1294,6 +1296,10 @@ symtable_visit_stmt(struct symtable *st, stmt_ty s)
if (s->v.If.orelse)
VISIT_SEQ(st, stmt, s->v.If.orelse);
break;
+ case Match_kind:
+ VISIT(st, expr, s->v.Match.subject);
+ VISIT_SEQ(st, match_case, s->v.Match.cases);
+ break;
case Raise_kind:
if (s->v.Raise.exc) {
VISIT(st, expr, s->v.Raise.exc);
@@ -1648,6 +1654,13 @@ symtable_visit_expr(struct symtable *st, expr_ty e)
VISIT(st, expr, e->v.Slice.step)
break;
case Name_kind:
+ // Don't make "_" a local when used in a pattern:
+ if (st->in_pattern &&
+ e->v.Name.ctx == Store &&
+ _PyUnicode_EqualToASCIIString(e->v.Name.id, "_"))
+ {
+ break;
+ }
if (!symtable_add_def(st, e->v.Name.id,
e->v.Name.ctx == Load ? USE : DEF_LOCAL))
VISIT_QUIT(st, 0);
@@ -1667,6 +1680,13 @@ symtable_visit_expr(struct symtable *st, expr_ty e)
case Tuple_kind:
VISIT_SEQ(st, expr, e->v.Tuple.elts);
break;
+ case MatchAs_kind:
+ VISIT(st, expr, e->v.MatchAs.pattern);
+ symtable_add_def(st, e->v.MatchAs.name, DEF_LOCAL);
+ break;
+ case MatchOr_kind:
+ VISIT_SEQ(st, expr, e->v.MatchOr.patterns);
+ break;
}
VISIT_QUIT(st, 1);
}
@@ -1785,6 +1805,20 @@ symtable_visit_withitem(struct symtable *st, withitem_ty item)
return 1;
}
+static int
+symtable_visit_match_case(struct symtable *st, match_case_ty m)
+{
+ assert(!st->in_pattern);
+ st->in_pattern = 1;
+ VISIT(st, expr, m->pattern);
+ assert(st->in_pattern);
+ st->in_pattern = 0;
+ if (m->guard) {
+ VISIT(st, expr, m->guard);
+ }
+ VISIT_SEQ(st, stmt, m->body);
+ return 1;
+}
static int
symtable_visit_alias(struct symtable *st, alias_ty a)