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Part 2 of 2: make "for (;;)" work

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This requires a gross but simple contract between pattern parsing and C
for loop parsing where pattern parsing will gracefully back out if and
only if we have a potential C for loop pattern AND assignment is
detected in the pattern (which isn't otherwise allowed outside of the
context of func decls).

If we ever want "for (((;;)))" to work, then this we'll need to
implement the fully general arbitrary token lookahead. But for now, the
common C style "just works".

Swift SVN r3831
This commit is contained in:
Dave Zarzycki
2013-01-22 08:59:45 +00:00
parent 041e91d6ad
commit ac4592fdca
4 changed files with 68 additions and 30 deletions
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35
lib/Parse/ParsePattern.cpp
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@@ -36,7 +36,8 @@ static bool parseCurriedFunctionArguments(Parser *parser,
// parseFunctionArguments parsed the first argument pattern.
// Parse additional curried argument clauses as long as we can.
while (parser->Tok.isAnyLParen()) {
NullablePtr<Pattern> pattern = parser->parsePatternTuple(
bool CForLoopHack = false;
NullablePtr<Pattern> pattern = parser->parsePatternTuple(CForLoopHack,
/*AllowInitExpr=*/true);
if (pattern.isNull())
return true;
@@ -82,8 +83,9 @@ static bool parseSelectorArgument(Parser *parser,
parser->diagnose(parser->Tok, diag::func_selector_with_not_one_argument);
return true;
}
NullablePtr<Pattern> bodyPattern = parser->parsePatternAtom();
bool CForLoopHack = false;
NullablePtr<Pattern> bodyPattern = parser->parsePatternAtom(CForLoopHack);
if (bodyPattern.isNull()) {
parser->skipUntil(tok::r_paren);
return true;
@@ -198,7 +200,9 @@ static bool parseSelectorFunctionArguments(Parser *parser,
bool Parser::parseFunctionArguments(SmallVectorImpl<Pattern*> &argPatterns,
SmallVectorImpl<Pattern*> &bodyPatterns) {
// Parse the first function argument clause.
NullablePtr<Pattern> pattern = parsePatternTuple(/*AllowInitExpr=*/true);
bool CForLoopHack = false;
NullablePtr<Pattern> pattern = parsePatternTuple(CForLoopHack,
/*AllowInitExpr=*/true);
if (pattern.isNull())
return true;
else {
@@ -246,9 +250,9 @@ bool Parser::parseFunctionSignature(SmallVectorImpl<Pattern*> &argPatterns,
/// Parse a pattern.
/// pattern ::= pattern-atom
/// pattern ::= pattern-atom ':' type-annotation
NullablePtr<Pattern> Parser::parsePattern() {
NullablePtr<Pattern> Parser::parsePattern(bool &CForLoopHack) {
// First, parse the pattern atom.
NullablePtr<Pattern> pattern = parsePatternAtom();
NullablePtr<Pattern> pattern = parsePatternAtom(CForLoopHack);
if (pattern.isNull()) return nullptr;
// Now parse an optional type annotation.
@@ -285,16 +289,18 @@ NullablePtr<Pattern> Parser::parsePatternIdentifier() {
///
/// pattern-atom ::= identifier
/// pattern-atom ::= pattern-tuple
NullablePtr<Pattern> Parser::parsePatternAtom() {
NullablePtr<Pattern> Parser::parsePatternAtom(bool &CForLoopHack) {
switch (Tok.getKind()) {
case tok::l_paren:
case tok::l_paren_space:
return parsePatternTuple(/*AllowInitExpr*/false);
return parsePatternTuple(CForLoopHack, /*AllowInitExpr*/false);
case tok::identifier:
CForLoopHack = false;
return parsePatternIdentifier();
default:
CForLoopHack = false;
diagnose(Tok, diag::expected_pattern);
return nullptr;
}
@@ -309,19 +315,28 @@ NullablePtr<Pattern> Parser::parsePatternAtom() {
/// pattern-tuple-element:
/// pattern ('=' expr)?
NullablePtr<Pattern> Parser::parsePatternTuple(bool AllowInitExpr) {
NullablePtr<Pattern> Parser::parsePatternTuple(bool &CForLoopHack,
bool AllowInitExpr) {
assert(Tok.isAnyLParen());
// We're looking at the left parenthesis; consume it.
SourceLoc lp = consumeToken();
// We have a gross hack/contract with c-style-for loop parsing
if (CForLoopHack && peekToken().is(tok::equal)) {
return nullptr;
} else {
CForLoopHack = false;
}
// Parse all the elements.
SmallVector<TuplePatternElt, 8> elts;
bool hadEllipsis = false;
bool Invalid = false;
if (Tok.isNot(tok::r_paren)) {
do {
NullablePtr<Pattern> pattern = parsePattern();
bool CForLoopHack = false;
NullablePtr<Pattern> pattern = parsePattern(CForLoopHack);
ExprHandle *init = nullptr;
if (pattern.isNull()) {