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[toolchain] Implement #623: require braces.

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For error recovery, allow the braces around the controlled statement of
an `if`, `while`, or similar to be omitted. Remove support for nested
code blocks as this conflicts with struct literal syntax.
This commit is contained in:
Richard Smith
2021-07-30 18:27:52 -07:00
parent 91512e90e7
commit f1028fcc27
3 changed files with 178 additions and 64 deletions
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toolchain/parser/parser_impl.cpp
+25 -9
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@@ -60,6 +60,11 @@ struct UnrecognizedDeclaration : SimpleDiagnostic<UnrecognizedDeclaration> {
"Unrecognized declaration introducer.";
};
struct ExpectedCodeBlock : SimpleDiagnostic<ExpectedCodeBlock> {
static constexpr llvm::StringLiteral ShortName = "syntax-error";
static constexpr llvm::StringLiteral Message = "Expected braced code block.";
};
struct ExpectedExpression : SimpleDiagnostic<ExpectedExpression> {
static constexpr llvm::StringLiteral ShortName = "syntax-error";
static constexpr llvm::StringLiteral Message = "Expected expression.";
@@ -480,8 +485,16 @@ auto ParseTree::Parser::ParseFunctionSignature() -> bool {
return params.hasValue();
}
auto ParseTree::Parser::ParseCodeBlock() -> Node {
TokenizedBuffer::Token open_curly = Consume(TokenKind::OpenCurlyBrace());
auto ParseTree::Parser::ParseCodeBlock() -> llvm::Optional<Node> {
llvm::Optional<TokenizedBuffer::Token> maybe_open_curly =
ConsumeIf(TokenKind::OpenCurlyBrace());
if (!maybe_open_curly) {
// Recover by parsing a single statement.
emitter.EmitError<ExpectedCodeBlock>(*position);
return ParseStatement();
}
TokenizedBuffer::Token open_curly = *maybe_open_curly;
auto start = GetSubtreeStartPosition();
bool has_errors = false;
@@ -549,7 +562,9 @@ auto ParseTree::Parser::ParseFunctionDeclaration() -> Node {
// See if we should parse a definition which is represented as a code block.
if (NextTokenIs(TokenKind::OpenCurlyBrace())) {
ParseCodeBlock();
if (!ParseCodeBlock()) {
return add_error_function_node();
}
} else if (!ConsumeAndAddLeafNodeIf(TokenKind::Semi(),
ParseNodeKind::DeclarationEnd())) {
emitter.EmitError<ExpectedFunctionBodyOrSemi>(*position);
@@ -978,11 +993,15 @@ auto ParseTree::Parser::ParseIfStatement() -> llvm::Optional<Node> {
auto start = GetSubtreeStartPosition();
auto if_token = Consume(TokenKind::IfKeyword());
auto cond = ParseParenCondition(TokenKind::IfKeyword());
auto then_case = ParseStatement();
auto then_case = ParseCodeBlock();
bool else_has_errors = false;
if (ConsumeAndAddLeafNodeIf(TokenKind::ElseKeyword(),
ParseNodeKind::IfStatementElse())) {
else_has_errors = !ParseStatement();
// 'else if' is permitted as a special case.
if (NextTokenIs(TokenKind::IfKeyword()))
else_has_errors = !ParseIfStatement();
else
else_has_errors = !ParseCodeBlock();
}
return AddNode(ParseNodeKind::IfStatement(), if_token, start,
/*has_error=*/!cond || !then_case || else_has_errors);
@@ -992,7 +1011,7 @@ auto ParseTree::Parser::ParseWhileStatement() -> llvm::Optional<Node> {
auto start = GetSubtreeStartPosition();
auto while_token = Consume(TokenKind::WhileKeyword());
auto cond = ParseParenCondition(TokenKind::WhileKeyword());
auto body = ParseStatement();
auto body = ParseCodeBlock();
return AddNode(ParseNodeKind::WhileStatement(), while_token, start,
/*has_error=*/!cond || !body);
}
@@ -1046,9 +1065,6 @@ auto ParseTree::Parser::ParseStatement() -> llvm::Optional<Node> {
return ParseKeywordStatement(ParseNodeKind::ReturnStatement(),
KeywordStatementArgument::Optional);
case TokenKind::OpenCurlyBrace():
return ParseCodeBlock();
default:
// A statement with no introducer token can only be an expression
// statement.