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Add soft keywords (GH-20370)

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These are like keywords but they only work in context; they are not reserved except when there is an exact match.

This would enable things like match statements without reserving `match` (which would be bad for the `re.match()` function and probably lots of other places).

Automerge-Triggered-By: @gvanrossum
This commit is contained in:
Guido van Rossum 2020-05-26 10:58:44 -07:00 • committed by GitHub
parent 578c3955e0
commit b45af1a569
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4 changed files with 75 additions and 4 deletions
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24
Tools/peg_generator/pegen/c_generator.py
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@ -117,6 +117,16 @@ class CCallMakerVisitor(GrammarVisitor):
comment=f"token='{keyword}'",
)
def soft_keyword_helper(self, value: str) -> FunctionCall:
return FunctionCall(
assigned_variable="_keyword",
function="_PyPegen_expect_soft_keyword",
arguments=["p", value],
return_type="expr_ty",
nodetype=NodeTypes.NAME_TOKEN,
comment=f"soft_keyword='{value}'",
)
def visit_NameLeaf(self, node: NameLeaf) -> FunctionCall:
name = node.value
if name in self.non_exact_tokens:
@ -154,7 +164,10 @@ class CCallMakerVisitor(GrammarVisitor):
def visit_StringLeaf(self, node: StringLeaf) -> FunctionCall:
val = ast.literal_eval(node.value)
if re.match(r"[a-zA-Z_]\w*\Z", val): # This is a keyword
return self.keyword_helper(val)
if node.value.endswith("'"):
return self.keyword_helper(val)
else:
return self.soft_keyword_helper(node.value)
else:
assert val in self.exact_tokens, f"{node.value} is not a known literal"
type = self.exact_tokens[val]
@ -656,8 +669,9 @@ class CParserGenerator(ParserGenerator, GrammarVisitor):
self.print("{")
# We have parsed successfully all the conditions for the option.
with self.indent():
node_str = str(node).replace('"', '\\"')
self.print(
f'D(fprintf(stderr, "%*c+ {rulename}[%d-%d]: %s succeeded!\\n", p->level, \' \', _mark, p->mark, "{node}"));'
f'D(fprintf(stderr, "%*c+ {rulename}[%d-%d]: %s succeeded!\\n", p->level, \' \', _mark, p->mark, "{node_str}"));'
)
# Prepare to emmit the rule action and do so
if node.action and "EXTRA" in node.action:
@ -710,8 +724,9 @@ class CParserGenerator(ParserGenerator, GrammarVisitor):
self.print(f"{{ // {node}")
with self.indent():
self._check_for_errors()
node_str = str(node).replace('"', '\\"')
self.print(
f'D(fprintf(stderr, "%*c> {rulename}[%d-%d]: %s\\n", p->level, \' \', _mark, p->mark, "{node}"));'
f'D(fprintf(stderr, "%*c> {rulename}[%d-%d]: %s\\n", p->level, \' \', _mark, p->mark, "{node_str}"));'
)
# Prepare variable declarations for the alternative
vars = self.collect_vars(node)
@ -733,9 +748,10 @@ class CParserGenerator(ParserGenerator, GrammarVisitor):
self.handle_alt_normal(node, is_gather, rulename)
self.print("p->mark = _mark;")
node_str = str(node).replace('"', '\\"')
self.print(
f"D(fprintf(stderr, \"%*c%s {rulename}[%d-%d]: %s failed!\\n\", p->level, ' ',\n"
f' p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "{node}"));'
f' p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "{node_str}"));'
)
if "_cut_var" in vars:
self.print("if (_cut_var) {")