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py/compile: Implement PEP 572, assignment expressions with := operator.

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The syntax matches CPython and the semantics are equivalent except that,
unlike CPython, MicroPython allows using := to assign to comprehension
iteration variables, because disallowing this would take a lot of code to
check for it.

The new compile-time option MICROPY_PY_ASSIGN_EXPR selects this feature and
is enabled by default, following MICROPY_PY_ASYNC_AWAIT.
This commit is contained in:
Damien George
2020-06-16 21:42:44 +10:00
parent 0fd91e39b1
commit 1783950311
6 changed files with 55 additions and 9 deletions
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29
py/compile.c
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@@ -3,7 +3,7 @@
*
* The MIT License (MIT)
*
* Copyright (c) 2013-2015 Damien P. George
* Copyright (c) 2013-2020 Damien P. George
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -2108,6 +2108,27 @@ STATIC void compile_lambdef(compiler_t *comp, mp_parse_node_struct_t *pns) {
compile_funcdef_lambdef(comp, this_scope, pns->nodes[0], PN_varargslist);
}
#if MICROPY_PY_ASSIGN_EXPR
STATIC void compile_namedexpr_helper(compiler_t *comp, mp_parse_node_t pn_name, mp_parse_node_t pn_expr) {
if (!MP_PARSE_NODE_IS_ID(pn_name)) {
compile_syntax_error(comp, (mp_parse_node_t)pn_name, MP_ERROR_TEXT("can't assign to expression"));
}
compile_node(comp, pn_expr);
EMIT(dup_top);
scope_t *old_scope = comp->scope_cur;
if (SCOPE_IS_COMP_LIKE(comp->scope_cur->kind)) {
// Use parent's scope for assigned value so it can "escape"
comp->scope_cur = comp->scope_cur->parent;
}
compile_store_id(comp, MP_PARSE_NODE_LEAF_ARG(pn_name));
comp->scope_cur = old_scope;
}
STATIC void compile_namedexpr(compiler_t *comp, mp_parse_node_struct_t *pns) {
compile_namedexpr_helper(comp, pns->nodes[0], pns->nodes[1]);
}
#endif
STATIC void compile_or_and_test(compiler_t *comp, mp_parse_node_struct_t *pns) {
bool cond = MP_PARSE_NODE_STRUCT_KIND(pns) == PN_or_test;
uint l_end = comp_next_label(comp);
@@ -2353,6 +2374,12 @@ STATIC void compile_trailer_paren_helper(compiler_t *comp, mp_parse_node_t pn_ar
star_flags |= MP_EMIT_STAR_FLAG_DOUBLE;
dblstar_args_node = pns_arg;
} else if (MP_PARSE_NODE_STRUCT_KIND(pns_arg) == PN_argument) {
#if MICROPY_PY_ASSIGN_EXPR
if (MP_PARSE_NODE_IS_STRUCT_KIND(pns_arg->nodes[1], PN_argument_4)) {
compile_namedexpr_helper(comp, pns_arg->nodes[0], ((mp_parse_node_struct_t *)pns_arg->nodes[1])->nodes[0]);
n_positional++;
} else
#endif
if (!MP_PARSE_NODE_IS_STRUCT_KIND(pns_arg->nodes[1], PN_comp_for)) {
if (!MP_PARSE_NODE_IS_ID(pns_arg->nodes[0])) {
compile_syntax_error(comp, (mp_parse_node_t)pns_arg, MP_ERROR_TEXT("LHS of keyword arg must be an id"));