mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-24 22:02:23 +01:00
Richard Smith
2c45cb3be8
We model `if a then b else` as a prefix operator for parsing precedence purposes. The rule that a statement starting with `if` is never an `if` expression is handled implicitly because the statement parser never invokes the expression parser for a statement starting with `if`. This exposed a bug in our diagnosis of the whitespace rule for prefix operators, which was incorrectly being applied to non-symbolic operators in some cases, and was producing a bogus second diagnostic in some cases, which is also fixed here.
439 lines
16 KiB
C++
439 lines
16 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
|
|
// Exceptions. See /LICENSE for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
|
|
#include "toolchain/parser/parser_context.h"
|
|
|
|
#include <cstdlib>
|
|
#include <memory>
|
|
#include <optional>
|
|
|
|
#include "common/check.h"
|
|
#include "toolchain/lexer/token_kind.h"
|
|
#include "toolchain/lexer/tokenized_buffer.h"
|
|
#include "toolchain/parser/parse_node_kind.h"
|
|
#include "toolchain/parser/parse_tree.h"
|
|
|
|
namespace Carbon {
|
|
|
|
// A relative location for characters in errors.
|
|
enum class RelativeLocation : int8_t {
|
|
Around,
|
|
After,
|
|
Before,
|
|
};
|
|
|
|
// Adapts RelativeLocation for use with formatv.
|
|
static auto operator<<(llvm::raw_ostream& out, RelativeLocation loc)
|
|
-> llvm::raw_ostream& {
|
|
switch (loc) {
|
|
case RelativeLocation::Around:
|
|
out << "around";
|
|
break;
|
|
case RelativeLocation::After:
|
|
out << "after";
|
|
break;
|
|
case RelativeLocation::Before:
|
|
out << "before";
|
|
break;
|
|
}
|
|
return out;
|
|
}
|
|
|
|
ParserContext::ParserContext(ParseTree& tree, TokenizedBuffer& tokens,
|
|
TokenDiagnosticEmitter& emitter,
|
|
llvm::raw_ostream* vlog_stream)
|
|
: tree_(&tree),
|
|
tokens_(&tokens),
|
|
emitter_(&emitter),
|
|
vlog_stream_(vlog_stream),
|
|
position_(tokens_->tokens().begin()),
|
|
end_(tokens_->tokens().end()) {
|
|
CARBON_CHECK(position_ != end_) << "Empty TokenizedBuffer";
|
|
--end_;
|
|
CARBON_CHECK(tokens_->GetKind(*end_) == TokenKind::EndOfFile)
|
|
<< "TokenizedBuffer should end with EndOfFile, ended with "
|
|
<< tokens_->GetKind(*end_);
|
|
}
|
|
|
|
auto ParserContext::AddLeafNode(ParseNodeKind kind,
|
|
TokenizedBuffer::Token token, bool has_error)
|
|
-> void {
|
|
tree_->node_impls_.push_back(
|
|
ParseTree::NodeImpl(kind, has_error, token, /*subtree_size=*/1));
|
|
if (has_error) {
|
|
tree_->has_errors_ = true;
|
|
}
|
|
}
|
|
|
|
auto ParserContext::AddNode(ParseNodeKind kind, TokenizedBuffer::Token token,
|
|
int subtree_start, bool has_error) -> void {
|
|
int subtree_size = tree_->size() - subtree_start + 1;
|
|
tree_->node_impls_.push_back(
|
|
ParseTree::NodeImpl(kind, has_error, token, subtree_size));
|
|
if (has_error) {
|
|
tree_->has_errors_ = true;
|
|
}
|
|
}
|
|
|
|
auto ParserContext::ConsumeAndAddOpenParen(TokenizedBuffer::Token default_token,
|
|
ParseNodeKind start_kind) -> void {
|
|
if (auto open_paren = ConsumeIf(TokenKind::OpenParen)) {
|
|
AddLeafNode(start_kind, *open_paren, /*has_error=*/false);
|
|
} else {
|
|
CARBON_DIAGNOSTIC(ExpectedParenAfter, Error, "Expected `(` after `{0}`.",
|
|
TokenKind);
|
|
emitter_->Emit(*position_, ExpectedParenAfter,
|
|
tokens().GetKind(default_token));
|
|
AddLeafNode(start_kind, default_token, /*has_error=*/true);
|
|
}
|
|
}
|
|
|
|
auto ParserContext::ConsumeAndAddCloseParen(StateStackEntry state,
|
|
ParseNodeKind close_kind) -> void {
|
|
// state.token should point at the introducer, with the paren one after the
|
|
// introducer.
|
|
auto expected_paren = *(TokenizedBuffer::TokenIterator(state.token) + 1);
|
|
|
|
if (tokens().GetKind(expected_paren) != TokenKind::OpenParen) {
|
|
AddNode(close_kind, state.token, state.subtree_start, /*has_error=*/true);
|
|
} else if (auto close_token = ConsumeIf(TokenKind::CloseParen)) {
|
|
AddNode(close_kind, *close_token, state.subtree_start, state.has_error);
|
|
} else {
|
|
// TODO: Include the location of the matching open_paren in the diagnostic.
|
|
CARBON_DIAGNOSTIC(ExpectedCloseParen, Error,
|
|
"Unexpected tokens before `)`.");
|
|
emitter_->Emit(*position_, ExpectedCloseParen);
|
|
|
|
SkipTo(tokens().GetMatchedClosingToken(expected_paren));
|
|
AddNode(close_kind, Consume(), state.subtree_start, /*has_error=*/true);
|
|
}
|
|
}
|
|
|
|
auto ParserContext::ConsumeAndAddLeafNodeIf(TokenKind token_kind,
|
|
ParseNodeKind node_kind) -> bool {
|
|
auto token = ConsumeIf(token_kind);
|
|
if (!token) {
|
|
return false;
|
|
}
|
|
|
|
AddLeafNode(node_kind, *token);
|
|
return true;
|
|
}
|
|
|
|
auto ParserContext::ConsumeChecked(TokenKind kind) -> TokenizedBuffer::Token {
|
|
CARBON_CHECK(PositionIs(kind))
|
|
<< "Required " << kind << ", found " << PositionKind();
|
|
return Consume();
|
|
}
|
|
|
|
auto ParserContext::ConsumeIf(TokenKind kind)
|
|
-> std::optional<TokenizedBuffer::Token> {
|
|
if (!PositionIs(kind)) {
|
|
return std::nullopt;
|
|
}
|
|
return Consume();
|
|
}
|
|
|
|
auto ParserContext::ConsumeIfPatternKeyword(TokenKind keyword_token,
|
|
ParserState keyword_state,
|
|
int subtree_start) -> void {
|
|
if (auto token = ConsumeIf(keyword_token)) {
|
|
PushState(ParserContext::StateStackEntry(
|
|
keyword_state, PrecedenceGroup::ForTopLevelExpression(),
|
|
PrecedenceGroup::ForTopLevelExpression(), *token, subtree_start));
|
|
}
|
|
}
|
|
|
|
auto ParserContext::FindNextOf(std::initializer_list<TokenKind> desired_kinds)
|
|
-> std::optional<TokenizedBuffer::Token> {
|
|
auto new_position = position_;
|
|
while (true) {
|
|
TokenizedBuffer::Token token = *new_position;
|
|
TokenKind kind = tokens().GetKind(token);
|
|
if (kind.IsOneOf(desired_kinds)) {
|
|
return token;
|
|
}
|
|
|
|
// Step to the next token at the current bracketing level.
|
|
if (kind.is_closing_symbol() || kind == TokenKind::EndOfFile) {
|
|
// There are no more tokens at this level.
|
|
return std::nullopt;
|
|
} else if (kind.is_opening_symbol()) {
|
|
new_position = TokenizedBuffer::TokenIterator(
|
|
tokens().GetMatchedClosingToken(token));
|
|
// Advance past the closing token.
|
|
++new_position;
|
|
} else {
|
|
++new_position;
|
|
}
|
|
}
|
|
}
|
|
|
|
auto ParserContext::SkipMatchingGroup() -> bool {
|
|
if (!PositionKind().is_opening_symbol()) {
|
|
return false;
|
|
}
|
|
|
|
SkipTo(tokens().GetMatchedClosingToken(*position_));
|
|
++position_;
|
|
return true;
|
|
}
|
|
|
|
auto ParserContext::SkipPastLikelyEnd(TokenizedBuffer::Token skip_root)
|
|
-> std::optional<TokenizedBuffer::Token> {
|
|
if (position_ == end_) {
|
|
return std::nullopt;
|
|
}
|
|
|
|
TokenizedBuffer::Line root_line = tokens().GetLine(skip_root);
|
|
int root_line_indent = tokens().GetIndentColumnNumber(root_line);
|
|
|
|
// We will keep scanning through tokens on the same line as the root or
|
|
// lines with greater indentation than root's line.
|
|
auto is_same_line_or_indent_greater_than_root =
|
|
[&](TokenizedBuffer::Token t) {
|
|
TokenizedBuffer::Line l = tokens().GetLine(t);
|
|
if (l == root_line) {
|
|
return true;
|
|
}
|
|
|
|
return tokens().GetIndentColumnNumber(l) > root_line_indent;
|
|
};
|
|
|
|
do {
|
|
if (PositionIs(TokenKind::CloseCurlyBrace)) {
|
|
// Immediately bail out if we hit an unmatched close curly, this will
|
|
// pop us up a level of the syntax grouping.
|
|
return std::nullopt;
|
|
}
|
|
|
|
// We assume that a semicolon is always intended to be the end of the
|
|
// current construct.
|
|
if (auto semi = ConsumeIf(TokenKind::Semi)) {
|
|
return semi;
|
|
}
|
|
|
|
// Skip over any matching group of tokens().
|
|
if (SkipMatchingGroup()) {
|
|
continue;
|
|
}
|
|
|
|
// Otherwise just step forward one token.
|
|
++position_;
|
|
} while (position_ != end_ &&
|
|
is_same_line_or_indent_greater_than_root(*position_));
|
|
|
|
return std::nullopt;
|
|
}
|
|
|
|
auto ParserContext::SkipTo(TokenizedBuffer::Token t) -> void {
|
|
CARBON_CHECK(t >= *position_) << "Tried to skip backwards from " << position_
|
|
<< " to " << TokenizedBuffer::TokenIterator(t);
|
|
position_ = TokenizedBuffer::TokenIterator(t);
|
|
CARBON_CHECK(position_ != end_) << "Skipped past EOF.";
|
|
}
|
|
|
|
// Determines whether the given token is considered to be the start of an
|
|
// operand according to the rules for infix operator parsing.
|
|
static auto IsAssumedStartOfOperand(TokenKind kind) -> bool {
|
|
return kind.IsOneOf({TokenKind::OpenParen, TokenKind::Identifier,
|
|
TokenKind::IntegerLiteral, TokenKind::RealLiteral,
|
|
TokenKind::StringLiteral});
|
|
}
|
|
|
|
// Determines whether the given token is considered to be the end of an
|
|
// operand according to the rules for infix operator parsing.
|
|
static auto IsAssumedEndOfOperand(TokenKind kind) -> bool {
|
|
return kind.IsOneOf({TokenKind::CloseParen, TokenKind::CloseCurlyBrace,
|
|
TokenKind::CloseSquareBracket, TokenKind::Identifier,
|
|
TokenKind::IntegerLiteral, TokenKind::RealLiteral,
|
|
TokenKind::StringLiteral});
|
|
}
|
|
|
|
// Determines whether the given token could possibly be the start of an
|
|
// operand. This is conservatively correct, and will never incorrectly return
|
|
// `false`, but can incorrectly return `true`.
|
|
static auto IsPossibleStartOfOperand(TokenKind kind) -> bool {
|
|
return !kind.IsOneOf({TokenKind::CloseParen, TokenKind::CloseCurlyBrace,
|
|
TokenKind::CloseSquareBracket, TokenKind::Comma,
|
|
TokenKind::Semi, TokenKind::Colon});
|
|
}
|
|
|
|
auto ParserContext::IsLexicallyValidInfixOperator() -> bool {
|
|
CARBON_CHECK(position_ != end_) << "Expected an operator token.";
|
|
|
|
bool leading_space = tokens().HasLeadingWhitespace(*position_);
|
|
bool trailing_space = tokens().HasTrailingWhitespace(*position_);
|
|
|
|
// If there's whitespace on both sides, it's an infix operator.
|
|
if (leading_space && trailing_space) {
|
|
return true;
|
|
}
|
|
|
|
// If there's whitespace on exactly one side, it's not an infix operator.
|
|
if (leading_space || trailing_space) {
|
|
return false;
|
|
}
|
|
|
|
// Otherwise, for an infix operator, the preceding token must be any close
|
|
// bracket, identifier, or literal and the next token must be an open paren,
|
|
// identifier, or literal.
|
|
if (position_ == tokens().tokens().begin() ||
|
|
!IsAssumedEndOfOperand(tokens().GetKind(*(position_ - 1))) ||
|
|
!IsAssumedStartOfOperand(tokens().GetKind(*(position_ + 1)))) {
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
auto ParserContext::IsTrailingOperatorInfix() -> bool {
|
|
if (position_ == end_) {
|
|
return false;
|
|
}
|
|
|
|
// An operator that follows the infix operator rules is parsed as
|
|
// infix, unless the next token means that it can't possibly be.
|
|
if (IsLexicallyValidInfixOperator() &&
|
|
IsPossibleStartOfOperand(tokens().GetKind(*(position_ + 1)))) {
|
|
return true;
|
|
}
|
|
|
|
// A trailing operator with leading whitespace that's not valid as infix is
|
|
// not valid at all. If the next token looks like the start of an operand,
|
|
// then parse as infix, otherwise as postfix. Either way we'll produce a
|
|
// diagnostic later on.
|
|
if (tokens().HasLeadingWhitespace(*position_) &&
|
|
IsAssumedStartOfOperand(tokens().GetKind(*(position_ + 1)))) {
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
auto ParserContext::DiagnoseOperatorFixity(OperatorFixity fixity) -> void {
|
|
if (!PositionKind().is_symbol()) {
|
|
// Whitespace-based fixity rules only apply to symbolic operators.
|
|
return;
|
|
}
|
|
|
|
if (fixity == OperatorFixity::Infix) {
|
|
// Infix operators must satisfy the infix operator rules.
|
|
if (!IsLexicallyValidInfixOperator()) {
|
|
CARBON_DIAGNOSTIC(BinaryOperatorRequiresWhitespace, Error,
|
|
"Whitespace missing {0} binary operator.",
|
|
RelativeLocation);
|
|
emitter_->Emit(*position_, BinaryOperatorRequiresWhitespace,
|
|
tokens().HasLeadingWhitespace(*position_)
|
|
? RelativeLocation::After
|
|
: (tokens().HasTrailingWhitespace(*position_)
|
|
? RelativeLocation::Before
|
|
: RelativeLocation::Around));
|
|
}
|
|
} else {
|
|
bool prefix = fixity == OperatorFixity::Prefix;
|
|
|
|
// Whitespace is not permitted between a symbolic pre/postfix operator and
|
|
// its operand.
|
|
if ((prefix ? tokens().HasTrailingWhitespace(*position_)
|
|
: tokens().HasLeadingWhitespace(*position_))) {
|
|
CARBON_DIAGNOSTIC(UnaryOperatorHasWhitespace, Error,
|
|
"Whitespace is not allowed {0} this unary operator.",
|
|
RelativeLocation);
|
|
emitter_->Emit(
|
|
*position_, UnaryOperatorHasWhitespace,
|
|
prefix ? RelativeLocation::After : RelativeLocation::Before);
|
|
} else if (IsLexicallyValidInfixOperator()) {
|
|
// Pre/postfix operators must not satisfy the infix operator rules.
|
|
CARBON_DIAGNOSTIC(UnaryOperatorRequiresWhitespace, Error,
|
|
"Whitespace is required {0} this unary operator.",
|
|
RelativeLocation);
|
|
emitter_->Emit(
|
|
*position_, UnaryOperatorRequiresWhitespace,
|
|
prefix ? RelativeLocation::Before : RelativeLocation::After);
|
|
}
|
|
}
|
|
}
|
|
|
|
auto ParserContext::ConsumeListToken(ParseNodeKind comma_kind,
|
|
TokenKind close_kind,
|
|
bool already_has_error) -> ListTokenKind {
|
|
if (!PositionIs(TokenKind::Comma) && !PositionIs(close_kind)) {
|
|
// Don't error a second time on the same element.
|
|
if (!already_has_error) {
|
|
CARBON_DIAGNOSTIC(UnexpectedTokenAfterListElement, Error,
|
|
"Expected `,` or `{0}`.", TokenKind);
|
|
emitter_->Emit(*position_, UnexpectedTokenAfterListElement, close_kind);
|
|
ReturnErrorOnState();
|
|
}
|
|
|
|
// Recover from the invalid token.
|
|
auto end_of_element = FindNextOf({TokenKind::Comma, close_kind});
|
|
// The lexer guarantees that parentheses are balanced.
|
|
CARBON_CHECK(end_of_element)
|
|
<< "missing matching `" << close_kind.opening_symbol() << "` for `"
|
|
<< close_kind << "`";
|
|
|
|
SkipTo(*end_of_element);
|
|
}
|
|
|
|
if (PositionIs(close_kind)) {
|
|
return ListTokenKind::Close;
|
|
} else {
|
|
AddLeafNode(comma_kind, Consume());
|
|
return PositionIs(close_kind) ? ListTokenKind::CommaClose
|
|
: ListTokenKind::Comma;
|
|
}
|
|
}
|
|
|
|
auto ParserContext::GetDeclarationContext() -> DeclarationContext {
|
|
// i == 0 is the file-level DeclarationScopeLoop. Additionally, i == 1 can be
|
|
// skipped because it will never be a DeclarationScopeLoop.
|
|
for (int i = state_stack_.size() - 1; i > 1; --i) {
|
|
// The declaration context is always the state _above_ a
|
|
// DeclarationScopeLoop.
|
|
if (state_stack_[i].state == ParserState::DeclarationScopeLoop) {
|
|
switch (state_stack_[i - 1].state) {
|
|
case ParserState::TypeDefinitionFinishAsClass:
|
|
return DeclarationContext::Class;
|
|
case ParserState::TypeDefinitionFinishAsInterface:
|
|
return DeclarationContext::Interface;
|
|
case ParserState::TypeDefinitionFinishAsNamedConstraint:
|
|
return DeclarationContext::NamedConstraint;
|
|
default:
|
|
llvm_unreachable("Missing handling for a declaration scope");
|
|
}
|
|
}
|
|
}
|
|
CARBON_CHECK(!state_stack_.empty() &&
|
|
state_stack_[0].state == ParserState::DeclarationScopeLoop);
|
|
return DeclarationContext::File;
|
|
}
|
|
|
|
auto ParserContext::RecoverFromDeclarationError(StateStackEntry state,
|
|
ParseNodeKind parse_node_kind,
|
|
bool skip_past_likely_end)
|
|
-> void {
|
|
auto token = state.token;
|
|
if (skip_past_likely_end) {
|
|
if (auto semi = SkipPastLikelyEnd(token)) {
|
|
token = *semi;
|
|
}
|
|
}
|
|
AddNode(parse_node_kind, token, state.subtree_start,
|
|
/*has_error=*/true);
|
|
}
|
|
|
|
auto ParserContext::EmitExpectedDeclarationSemiOrDefinition(
|
|
TokenKind expected_kind) -> void {
|
|
CARBON_DIAGNOSTIC(ExpectedDeclarationSemiOrDefinition, Error,
|
|
"`{0}` should either end with a `;` for a declaration or "
|
|
"have a `{{ ... }` block for a definition.",
|
|
TokenKind);
|
|
emitter().Emit(*position(), ExpectedDeclarationSemiOrDefinition,
|
|
expected_kind);
|
|
}
|
|
|
|
} // namespace Carbon
|