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/Grammar/python.gram b/Grammar/python.gram
index bb70bbb..a225664 100644
--- a/Grammar/python.gram
+++ b/Grammar/python.gram
@@ -85,6 +85,7 @@
| &('for' | ASYNC) for_stmt
| &'try' try_stmt
| &'while' while_stmt
+ | match_stmt
# NOTE: annotated_rhs may start with 'yield'; yield_expr must start with 'yield'
assignment[stmt_ty]:
@@ -207,6 +208,114 @@
| invalid_except_block
finally_block[asdl_stmt_seq*]: 'finally' ':' a=block { a }
+match_stmt[stmt_ty]:
+ | "match" subject=subject_expr ':' NEWLINE INDENT cases[asdl_match_case_seq*]=case_block+ DEDENT {
+ CHECK_VERSION(stmt_ty, 10, "Pattern matching is", _Py_Match(subject, cases, EXTRA)) }
+subject_expr[expr_ty]:
+ | value=star_named_expression ',' values=star_named_expressions? {
+ _Py_Tuple(CHECK(asdl_expr_seq*, _PyPegen_seq_insert_in_front(p, value, values)), Load, EXTRA) }
+ | named_expression
+case_block[match_case_ty]:
+ | "case" pattern=patterns guard=guard? ':' body=block {
+ _Py_match_case(pattern, guard, body, p->arena) }
+guard[expr_ty]: 'if' guard=named_expression { guard }
+
+patterns[expr_ty]:
+ | values[asdl_expr_seq*]=open_sequence_pattern {
+ _Py_Tuple(values, Load, EXTRA) }
+ | pattern
+pattern[expr_ty]:
+ | as_pattern
+ | or_pattern
+as_pattern[expr_ty]:
+ | pattern=or_pattern 'as' target=capture_pattern {
+ _Py_MatchAs(pattern, target->v.Name.id, EXTRA) }
+or_pattern[expr_ty]:
+ | patterns[asdl_expr_seq*]='|'.closed_pattern+ {
+ asdl_seq_LEN(patterns) == 1 ? asdl_seq_GET(patterns, 0) : _Py_MatchOr(patterns, EXTRA) }
+closed_pattern[expr_ty]:
+ | literal_pattern
+ | capture_pattern
+ | wildcard_pattern
+ | value_pattern
+ | group_pattern
+ | sequence_pattern
+ | mapping_pattern
+ | class_pattern
+
+literal_pattern[expr_ty]:
+ | signed_number !('+' | '-')
+ | real=signed_number '+' imag=NUMBER { _Py_BinOp(real, Add, imag, EXTRA) }
+ | real=signed_number '-' imag=NUMBER { _Py_BinOp(real, Sub, imag, EXTRA) }
+ | strings
+ | 'None' { _Py_Constant(Py_None, NULL, EXTRA) }
+ | 'True' { _Py_Constant(Py_True, NULL, EXTRA) }
+ | 'False' { _Py_Constant(Py_False, NULL, EXTRA) }
+signed_number[expr_ty]:
+ | NUMBER
+ | '-' number=NUMBER { _Py_UnaryOp(USub, number, EXTRA) }
+
+capture_pattern[expr_ty]:
+ | !"_" name=NAME !('.' | '(' | '=') {
+ _PyPegen_set_expr_context(p, name, Store) }
+
+wildcard_pattern[expr_ty]:
+ | "_" { _Py_Name(CHECK(PyObject*, _PyPegen_new_identifier(p, "_")), Store, EXTRA) }
+
+value_pattern[expr_ty]:
+ | attr=attr !('.' | '(' | '=') { attr }
+attr[expr_ty]:
+ | value=name_or_attr '.' attr=NAME {
+ _Py_Attribute(value, attr->v.Name.id, Load, EXTRA) }
+name_or_attr[expr_ty]:
+ | attr
+ | NAME
+
+group_pattern[expr_ty]:
+ | '(' pattern=pattern ')' { pattern }
+
+sequence_pattern[expr_ty]:
+ | '[' values=maybe_sequence_pattern? ']' { _Py_List(values, Load, EXTRA) }
+ | '(' values=open_sequence_pattern? ')' { _Py_Tuple(values, Load, EXTRA) }
+open_sequence_pattern[asdl_seq*]:
+ | value=maybe_star_pattern ',' values=maybe_sequence_pattern? {
+ _PyPegen_seq_insert_in_front(p, value, values) }
+maybe_sequence_pattern[asdl_seq*]:
+ | values=','.maybe_star_pattern+ ','? { values }
+maybe_star_pattern[expr_ty]:
+ | star_pattern
+ | pattern
+star_pattern[expr_ty]:
+ | '*' value=(capture_pattern | wildcard_pattern) {
+ _Py_Starred(value, Store, EXTRA) }
+
+mapping_pattern[expr_ty]:
+ | '{' items=items_pattern? '}' {
+ _Py_Dict(CHECK(asdl_expr_seq*, _PyPegen_get_keys(p, items)), CHECK(asdl_expr_seq*, _PyPegen_get_values(p, items)), EXTRA) }
+items_pattern[asdl_seq*]:
+ | items=','.key_value_pattern+ ','? { items }
+key_value_pattern[KeyValuePair*]:
+ | key=(literal_pattern | value_pattern) ':' value=pattern {
+ _PyPegen_key_value_pair(p, key, value) }
+ | double_star_pattern
+double_star_pattern[KeyValuePair*]:
+ | '**' value=capture_pattern { _PyPegen_key_value_pair(p, NULL, value) }
+
+class_pattern[expr_ty]:
+ | func=name_or_attr '(' ')' { _Py_Call(func, NULL, NULL, EXTRA) }
+ | func=name_or_attr '(' args=positional_patterns ','? ')' {
+ _Py_Call(func, args, NULL, EXTRA) }
+ | func=name_or_attr '(' keywords=keyword_patterns ','? ')' {
+ _Py_Call(func, NULL, keywords, EXTRA) }
+ | func=name_or_attr '(' args=positional_patterns ',' keywords=keyword_patterns ','? ')' {
+ _Py_Call(func, args, keywords, EXTRA) }
+positional_patterns[asdl_expr_seq*]:
+ | args[asdl_expr_seq*]=','.pattern+ { args }
+keyword_patterns[asdl_keyword_seq*]:
+ | keywords[asdl_keyword_seq*]=','.keyword_pattern+ { keywords }
+keyword_pattern[keyword_ty]:
+ | arg=NAME '=' value=pattern { _Py_keyword(arg->v.Name.id, value, EXTRA) }
+
return_stmt[stmt_ty]:
| 'return' a=[star_expressions] { _Py_Return(a, EXTRA) }
@@ -676,7 +785,7 @@
RAISE_SYNTAX_ERROR_INVALID_TARGET(STAR_TARGETS, a) }
| (star_targets '=')* a=yield_expr '=' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "assignment to yield expression not possible") }
| a=star_expressions augassign (yield_expr | star_expressions) {
- RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
+ RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
a,
"'%s' is an illegal expression for augmented assignment",
_PyPegen_get_expr_name(a)