HLSL: 1) Implement lookahead buffers/stacks for token advance/recede, 2) use it for cast operation.
The grammar now accepts type casts, like "(int)x", but that
has to be disambiguated from "(a + b)", needed deeper lookahead
and backing up than what existed so far.
diff --git a/hlsl/hlslGrammar.cpp b/hlsl/hlslGrammar.cpp
index a6387b7..ddb7078 100755
--- a/hlsl/hlslGrammar.cpp
+++ b/hlsl/hlslGrammar.cpp
@@ -602,7 +602,8 @@
}
// unary_expression
-// : + unary_expression
+// : (type) unary_expression
+// | + unary_expression
// | - unary_expression
// | ! unary_expression
// | ~ unary_expression
@@ -612,9 +613,46 @@
//
bool HlslGrammar::acceptUnaryExpression(TIntermTyped*& node)
{
+ // (type) unary_expression
+ // Have to look two steps ahead, because this could be, e.g., a
+ // postfix_expression instead, since that also starts with at "(".
+ if (acceptTokenClass(EHTokLeftParen)) {
+ TType castType;
+ if (acceptType(castType)) {
+ if (! acceptTokenClass(EHTokRightParen)) {
+ expected("right parenthesis");
+ return false;
+ }
+
+ // We've matched "(type)" now, get the expression to cast
+ TSourceLoc loc = token.loc;
+ if (! acceptUnaryExpression(node))
+ return false;
+
+ // Hook it up like a constructor
+ TFunction* constructorFunction = parseContext.handleConstructorCall(loc, castType);
+ if (constructorFunction == nullptr) {
+ expected("type that can be constructed");
+ return false;
+ }
+ TIntermTyped* arguments = nullptr;
+ parseContext.handleFunctionArgument(constructorFunction, arguments, node);
+ node = parseContext.handleFunctionCall(loc, constructorFunction, arguments);
+
+ return true;
+ } else {
+ // This isn't a type cast, but it still started "(", so if it is a
+ // unary expression, it can only be a postfix_expression, so try that.
+ // Back it up first.
+ recedeToken();
+ return acceptPostfixExpression(node);
+ }
+ }
+
+ // peek for "op unary_expression"
TOperator unaryOp = HlslOpMap::preUnary(peek());
- // postfix_expression
+ // postfix_expression (if no unary operator)
if (unaryOp == EOpNull)
return acceptPostfixExpression(node);