Add new shift expression grammar rule.

This CL adds the `shift_expression.post.unary_expression` grammar
rule into the WGSL parser.

Bug: tint:1633
Change-Id: I833ddb05399afe8c792bd0b1abf3eda7f1d114e7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/99760
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/tint/reader/wgsl/parser_impl.cc

@@ -2800,6 +2800,41 @@ Maybe<const ast::Expression*> ParserImpl::element_count_expression() {
     return math.value;
 }
 
+// shift_expression.post.unary_expression
+//   : multiplicative_expression.post.unary_expression?
+//   | SHIFT_LEFT unary_expression
+//   | SHIFT_RIGHT unary_expression
+//
+// Note, add the `multiplicative_expression.post.unary_expression` is added here to make
+// implementation simpler.
+Expect<const ast::Expression*> ParserImpl::expect_shift_expression_post_unary_expression(
+    const ast::Expression* lhs) {
+    auto& t = peek();
+    if (match(Token::Type::kShiftLeft) || match(Token::Type::kShiftRight)) {
+        std::string name;
+        ast::BinaryOp op = ast::BinaryOp::kNone;
+        if (t.Is(Token::Type::kShiftLeft)) {
+            op = ast::BinaryOp::kShiftLeft;
+            name = "<<";
+        } else if (t.Is(Token::Type::kShiftRight)) {
+            op = ast::BinaryOp::kShiftRight;
+            name = ">>";
+        }
+
+        auto rhs = unary_expression();
+        if (rhs.errored) {
+            return Failure::kErrored;
+        }
+        if (!rhs.matched) {
+            return add_error(t,
+                             std::string("unable to parse right side of ") + name + " expression");
+        }
+        return create<ast::BinaryExpression>(t.source(), op, lhs, rhs.value);
+    }
+
+    return expect_multiplicative_expression_post_unary_expression(lhs);
+}
+
 // singular_expression
 //   : primary_expression postfix_expr
 Maybe<const ast::Expression*> ParserImpl::singular_expression() {

src/tint/reader/wgsl/parser_impl.h

@@ -667,6 +667,11 @@ class ParserImpl {
     /// Parses an `element_count_expression` grammar element
     /// @returns the parsed expression or nullptr
     Maybe<const ast::Expression*> element_count_expression();
+    /// Parses a `shift_expression.post.unary_expression` grammar element
+    /// @param lhs the left side of the expression
+    /// @returns the parsed expression or `lhs` if no match
+    Expect<const ast::Expression*> expect_shift_expression_post_unary_expression(
+        const ast::Expression* lhs);
     /// Parse the `additive_operator` grammar element
     /// @returns the parsed operator if successful
     Maybe<ast::BinaryOp> additive_operator();

src/tint/reader/wgsl/parser_impl_shift_expression_test.cc

@@ -17,7 +17,7 @@
 namespace tint::reader::wgsl {
 namespace {
 
-TEST_F(ParserImplTest, ShiftExpression_Parses_ShiftLeft) {
+TEST_F(ParserImplTest, ShiftExpression_Orig_Parses_ShiftLeft) {
     auto p = parser("a << true");
     auto e = p->shift_expression();
     EXPECT_TRUE(e.matched);
@@ -42,7 +42,7 @@ TEST_F(ParserImplTest, ShiftExpression_Parses_ShiftLeft) {
     ASSERT_TRUE(rel->rhs->As<ast::BoolLiteralExpression>()->value);
 }
 
-TEST_F(ParserImplTest, ShiftExpression_Parses_ShiftRight) {
+TEST_F(ParserImplTest, ShiftExpression_Orig_Parses_ShiftRight) {
     auto p = parser("a >> true");
     auto e = p->shift_expression();
     EXPECT_TRUE(e.matched);
@@ -67,7 +67,7 @@ TEST_F(ParserImplTest, ShiftExpression_Parses_ShiftRight) {
     ASSERT_TRUE(rel->rhs->As<ast::BoolLiteralExpression>()->value);
 }
 
-TEST_F(ParserImplTest, ShiftExpression_InvalidSpaceLeft) {
+TEST_F(ParserImplTest, ShiftExpression_Orig_InvalidSpaceLeft) {
     auto p = parser("a < < true");
     auto e = p->shift_expression();
     EXPECT_TRUE(e.matched);
@@ -76,7 +76,7 @@ TEST_F(ParserImplTest, ShiftExpression_InvalidSpaceLeft) {
     EXPECT_FALSE(e.value->Is<ast::BinaryExpression>());
 }
 
-TEST_F(ParserImplTest, ShiftExpression_InvalidSpaceRight) {
+TEST_F(ParserImplTest, ShiftExpression_Orig_InvalidSpaceRight) {
     auto p = parser("a > > true");
     auto e = p->shift_expression();
     EXPECT_TRUE(e.matched);
@@ -85,7 +85,7 @@ TEST_F(ParserImplTest, ShiftExpression_InvalidSpaceRight) {
     EXPECT_FALSE(e.value->Is<ast::BinaryExpression>());
 }
 
-TEST_F(ParserImplTest, ShiftExpression_InvalidLHS) {
+TEST_F(ParserImplTest, ShiftExpression_Orig_InvalidLHS) {
     auto p = parser("if (a) {} << true");
     auto e = p->shift_expression();
     EXPECT_FALSE(e.matched);
@@ -94,7 +94,7 @@ TEST_F(ParserImplTest, ShiftExpression_InvalidLHS) {
     EXPECT_EQ(e.value, nullptr);
 }
 
-TEST_F(ParserImplTest, ShiftExpression_InvalidRHS) {
+TEST_F(ParserImplTest, ShiftExpression_Orig_InvalidRHS) {
     auto p = parser("true << if (a) {}");
     auto e = p->shift_expression();
     EXPECT_FALSE(e.matched);
@@ -104,7 +104,7 @@ TEST_F(ParserImplTest, ShiftExpression_InvalidRHS) {
     EXPECT_EQ(p->error(), "1:9: unable to parse right side of << expression");
 }
 
-TEST_F(ParserImplTest, ShiftExpression_NoOr_ReturnsLHS) {
+TEST_F(ParserImplTest, ShiftExpression_Orig_NoOr_ReturnsLHS) {
     auto p = parser("a true");
     auto e = p->shift_expression();
     EXPECT_TRUE(e.matched);
@@ -114,5 +114,114 @@ TEST_F(ParserImplTest, ShiftExpression_NoOr_ReturnsLHS) {
     ASSERT_TRUE(e->Is<ast::IdentifierExpression>());
 }
 
+TEST_F(ParserImplTest, ShiftExpression_Parses_ShiftLeft) {
+    auto p = parser("a << true");
+    auto lhs = p->unary_expression();
+    auto e = p->expect_shift_expression_post_unary_expression(lhs.value);
+    EXPECT_FALSE(e.errored);
+    EXPECT_FALSE(p->has_error()) << p->error();
+    ASSERT_NE(e.value, nullptr);
+
+    EXPECT_EQ(e->source.range.begin.line, 1u);
+    EXPECT_EQ(e->source.range.begin.column, 3u);
+    EXPECT_EQ(e->source.range.end.line, 1u);
+    EXPECT_EQ(e->source.range.end.column, 5u);
+
+    ASSERT_TRUE(e->Is<ast::BinaryExpression>());
+    auto* rel = e->As<ast::BinaryExpression>();
+    EXPECT_EQ(ast::BinaryOp::kShiftLeft, rel->op);
+
+    ASSERT_TRUE(rel->lhs->Is<ast::IdentifierExpression>());
+    auto* ident = rel->lhs->As<ast::IdentifierExpression>();
+    EXPECT_EQ(ident->symbol, p->builder().Symbols().Get("a"));
+
+    ASSERT_TRUE(rel->rhs->Is<ast::BoolLiteralExpression>());
+    ASSERT_TRUE(rel->rhs->As<ast::BoolLiteralExpression>()->value);
+}
+
+TEST_F(ParserImplTest, ShiftExpression_Parses_ShiftRight) {
+    auto p = parser("a >> true");
+    auto lhs = p->unary_expression();
+    auto e = p->expect_shift_expression_post_unary_expression(lhs.value);
+    EXPECT_FALSE(e.errored);
+    EXPECT_FALSE(p->has_error()) << p->error();
+    ASSERT_NE(e.value, nullptr);
+
+    EXPECT_EQ(e->source.range.begin.line, 1u);
+    EXPECT_EQ(e->source.range.begin.column, 3u);
+    EXPECT_EQ(e->source.range.end.line, 1u);
+    EXPECT_EQ(e->source.range.end.column, 5u);
+
+    ASSERT_TRUE(e->Is<ast::BinaryExpression>());
+    auto* rel = e->As<ast::BinaryExpression>();
+    EXPECT_EQ(ast::BinaryOp::kShiftRight, rel->op);
+
+    ASSERT_TRUE(rel->lhs->Is<ast::IdentifierExpression>());
+    auto* ident = rel->lhs->As<ast::IdentifierExpression>();
+    EXPECT_EQ(ident->symbol, p->builder().Symbols().Get("a"));
+
+    ASSERT_TRUE(rel->rhs->Is<ast::BoolLiteralExpression>());
+    ASSERT_TRUE(rel->rhs->As<ast::BoolLiteralExpression>()->value);
+}
+
+TEST_F(ParserImplTest, ShiftExpression_Parses_Multiplicative) {
+    auto p = parser("a * b");
+    auto lhs = p->unary_expression();
+    auto e = p->expect_shift_expression_post_unary_expression(lhs.value);
+    EXPECT_FALSE(e.errored);
+    EXPECT_FALSE(p->has_error()) << p->error();
+    ASSERT_NE(e.value, nullptr);
+
+    ASSERT_TRUE(e->Is<ast::BinaryExpression>());
+    auto* rel = e->As<ast::BinaryExpression>();
+    EXPECT_EQ(ast::BinaryOp::kMultiply, rel->op);
+
+    ASSERT_TRUE(rel->lhs->Is<ast::IdentifierExpression>());
+    auto* ident = rel->lhs->As<ast::IdentifierExpression>();
+    EXPECT_EQ(ident->symbol, p->builder().Symbols().Get("a"));
+
+    ASSERT_TRUE(rel->rhs->Is<ast::IdentifierExpression>());
+    ident = rel->rhs->As<ast::IdentifierExpression>();
+    EXPECT_EQ(ident->symbol, p->builder().Symbols().Get("b"));
+}
+
+TEST_F(ParserImplTest, ShiftExpression_InvalidSpaceLeft) {
+    auto p = parser("a < < true");
+    auto lhs = p->unary_expression();
+    auto e = p->expect_shift_expression_post_unary_expression(lhs.value);
+    EXPECT_FALSE(e.errored);
+    ASSERT_NE(e.value, nullptr);
+    EXPECT_FALSE(e.value->Is<ast::BinaryExpression>());
+}
+
+TEST_F(ParserImplTest, ShiftExpression_InvalidSpaceRight) {
+    auto p = parser("a > > true");
+    auto lhs = p->unary_expression();
+    auto e = p->expect_shift_expression_post_unary_expression(lhs.value);
+    EXPECT_FALSE(e.errored);
+    ASSERT_NE(e.value, nullptr);
+    EXPECT_FALSE(e.value->Is<ast::BinaryExpression>());
+}
+
+TEST_F(ParserImplTest, ShiftExpression_InvalidRHS) {
+    auto p = parser("a << if (a) {}");
+    auto lhs = p->unary_expression();
+    auto e = p->expect_shift_expression_post_unary_expression(lhs.value);
+    EXPECT_TRUE(e.errored);
+    EXPECT_TRUE(p->has_error());
+    EXPECT_EQ(e.value, nullptr);
+    EXPECT_EQ(p->error(), "1:3: unable to parse right side of << expression");
+}
+
+TEST_F(ParserImplTest, ShiftExpression_NoOr_ReturnsLHS) {
+    auto p = parser("a true");
+    auto lhs = p->unary_expression();
+    auto e = p->expect_shift_expression_post_unary_expression(lhs.value);
+    EXPECT_FALSE(e.errored);
+    EXPECT_FALSE(p->has_error()) << p->error();
+    ASSERT_NE(e.value, nullptr);
+    ASSERT_EQ(lhs.value, e.value);
+}
+
 }  // namespace
 }  // namespace tint::reader::wgsl