Add `@must_use` AST node.

This CL adds the `@must_use` ast node and hooks it into the
program_builder.

Bug: tint:1844
Change-Id: I2ffe99bbf29ec287446788253aa8cf63cc4da50b
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/120820
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/tint/BUILD.gn

@@ -490,6 +490,7 @@ libtint_source_set("libtint_ast_hdrs") {
     "ast/loop_statement.h",
     "ast/member_accessor_expression.h",
     "ast/module.h",
+    "ast/must_use_attribute.h",
     "ast/node.h",
     "ast/node_id.h",
     "ast/override.h",
@@ -575,6 +576,7 @@ libtint_source_set("libtint_ast_src") {
     "ast/loop_statement.cc",
     "ast/member_accessor_expression.cc",
     "ast/module.cc",
+    "ast/must_use_attribute.cc",
     "ast/node.cc",
     "ast/override.cc",
     "ast/parameter.cc",
@@ -1268,7 +1270,6 @@ if (tint_build_unittests) {
       "ast/index_accessor_expression_test.cc",
       "ast/int_literal_expression_test.cc",
       "ast/interpolate_attribute_test.cc",
-      "ast/invariant_attribute_test.cc",
       "ast/location_attribute_test.cc",
       "ast/loop_statement_test.cc",
       "ast/member_accessor_expression_test.cc",

src/tint/CMakeLists.txt

@@ -174,6 +174,8 @@ list(APPEND TINT_LIB_SRCS
   ast/member_accessor_expression.h
   ast/module.cc
   ast/module.h
+  ast/must_use_attribute.cc
+  ast/must_use_attribute.h
   ast/node_id.h
   ast/node.cc
   ast/node.h
@@ -831,7 +833,6 @@ if(TINT_BUILD_TESTS)
     ast/index_accessor_expression_test.cc
     ast/int_literal_expression_test.cc
     ast/interpolate_attribute_test.cc
-    ast/invariant_attribute_test.cc
     ast/location_attribute_test.cc
     ast/loop_statement_test.cc
     ast/member_accessor_expression_test.cc

src/tint/ast/invariant_attribute_test.cc

@@ -1,25 +0,0 @@
-// Copyright 2021 The Tint Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#include "src/tint/ast/invariant_attribute.h"
-
-#include "src/tint/ast/test_helper.h"
-
-namespace tint::ast {
-namespace {
-
-using InvariantAttributeTest = TestHelper;
-
-}  // namespace
-}  // namespace tint::ast

src/tint/ast/must_use_attribute.cc

@@ -0,0 +1,38 @@
+// Copyright 2023 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/tint/ast/must_use_attribute.h"
+
+#include "src/tint/program_builder.h"
+
+TINT_INSTANTIATE_TYPEINFO(tint::ast::MustUseAttribute);
+
+namespace tint::ast {
+
+MustUseAttribute::MustUseAttribute(ProgramID pid, NodeID nid, const Source& src)
+    : Base(pid, nid, src) {}
+
+MustUseAttribute::~MustUseAttribute() = default;
+
+std::string MustUseAttribute::Name() const {
+    return "must_use";
+}
+
+const MustUseAttribute* MustUseAttribute::Clone(CloneContext* ctx) const {
+    // Clone arguments outside of create() call to have deterministic ordering
+    auto src = ctx->Clone(source);
+    return ctx->dst->create<MustUseAttribute>(src);
+}
+
+}  // namespace tint::ast

src/tint/ast/must_use_attribute.h

@@ -0,0 +1,46 @@
+// Copyright 2023 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef SRC_TINT_AST_MUST_USE_ATTRIBUTE_H_
+#define SRC_TINT_AST_MUST_USE_ATTRIBUTE_H_
+
+#include <string>
+
+#include "src/tint/ast/attribute.h"
+
+namespace tint::ast {
+
+/// The must_use attribute
+class MustUseAttribute final : public Castable<MustUseAttribute, Attribute> {
+  public:
+    /// constructor
+    /// @param pid the identifier of the program that owns this node
+    /// @param nid the unique node identifier
+    /// @param src the source of this node
+    MustUseAttribute(ProgramID pid, NodeID nid, const Source& src);
+    ~MustUseAttribute() override;
+
+    /// @returns the WGSL name for the attribute
+    std::string Name() const override;
+
+    /// Clones this node and all transitive child nodes using the `CloneContext`
+    /// `ctx`.
+    /// @param ctx the clone context
+    /// @return the newly cloned node
+    const MustUseAttribute* Clone(CloneContext* ctx) const override;
+};
+
+}  // namespace tint::ast
+
+#endif  // SRC_TINT_AST_MUST_USE_ATTRIBUTE_H_

src/tint/ir/builder_impl.cc

@@ -800,6 +800,9 @@ bool BuilderImpl::EmitAttribute(const ast::Attribute* attr) {
         // [&](const ast::InvariantAttribute* i) {
         // TODO(dsinclair): Implement
         // },
+        // [&](const ast::MustUseAttribute* i) {
+        // TODO(dsinclair): Implement
+        // },
         [&](const ast::IdAttribute*) {
             diagnostics_.add_warning(tint::diag::System::IR,
                                      "found an `Id` attribute. The SubstituteOverrides transform "

src/tint/program_builder.h

@@ -56,6 +56,7 @@
 #include "src/tint/ast/loop_statement.h"
 #include "src/tint/ast/member_accessor_expression.h"
 #include "src/tint/ast/module.h"
+#include "src/tint/ast/must_use_attribute.h"
 #include "src/tint/ast/override.h"
 #include "src/tint/ast/parameter.h"
 #include "src/tint/ast/phony_expression.h"
@@ -3504,6 +3505,17 @@ class ProgramBuilder {
     /// @returns the invariant attribute pointer
     const ast::InvariantAttribute* Invariant() { return create<ast::InvariantAttribute>(source_); }
 
+    /// Creates an ast::MustUseAttribute
+    /// @param source the source information
+    /// @returns the invariant attribute pointer
+    const ast::MustUseAttribute* MustUse(const Source& source) {
+        return create<ast::MustUseAttribute>(source);
+    }
+
+    /// Creates an ast::MustUseAttribute
+    /// @returns the invariant attribute pointer
+    const ast::MustUseAttribute* MustUse() { return create<ast::MustUseAttribute>(source_); }
+
     /// Creates an ast::LocationAttribute
     /// @param source the source information
     /// @param location the location value expression

src/tint/reader/wgsl/parser_impl.cc

@@ -85,12 +85,12 @@ bool is_reserved(const Token& t) {
            t == "finally" || t == "friend" || t == "from" || t == "fxgroup" || t == "get" ||
            t == "goto" || t == "groupshared" || t == "handle" || t == "highp" || t == "impl" ||
            t == "implements" || t == "import" || t == "inline" || t == "inout" ||
-           t == "instanceof" || t == "interface" || t == "invariant" || t == "layout" ||
+           t == "instanceof" || t == "interface" || t == "layout" || t == "lowp" || t == "macro" ||
-           t == "lowp" || t == "macro" || t == "macro_rules" || t == "match" || t == "mediump" ||
+           t == "macro_rules" || t == "match" || t == "mediump" || t == "meta" || t == "mod" ||
-           t == "meta" || t == "mod" || t == "module" || t == "move" || t == "mut" ||
+           t == "module" || t == "move" || t == "mut" || t == "mutable" || t == "namespace" ||
-           t == "mutable" || t == "namespace" || t == "new" || t == "nil" || t == "noexcept" ||
+           t == "new" || t == "nil" || t == "noexcept" || t == "noinline" ||
-           t == "noinline" || t == "nointerpolation" || t == "noperspective" || t == "null" ||
+           t == "nointerpolation" || t == "noperspective" || t == "null" || t == "nullptr" ||
-           t == "nullptr" || t == "of" || t == "operator" || t == "package" || t == "packoffset" ||
+           t == "of" || t == "operator" || t == "package" || t == "packoffset" ||
            t == "partition" || t == "pass" || t == "patch" || t == "pixelfragment" ||
            t == "precise" || t == "precision" || t == "premerge" || t == "priv" ||
            t == "protected" || t == "pub" || t == "public" || t == "readonly" || t == "ref" ||

src/tint/reader/wgsl/parser_impl_reserved_keyword_test.cc

@@ -152,7 +152,6 @@ INSTANTIATE_TEST_SUITE_P(ParserImplReservedKeywordTest,
                                          "inout",
                                          "instanceof",
                                          "interface",
-                                         "invariant",
                                          "layout",
                                          "lowp",
                                          "macro",

src/tint/resolver/dependency_graph.cc

@@ -39,6 +39,7 @@
 #include "src/tint/ast/invariant_attribute.h"
 #include "src/tint/ast/location_attribute.h"
 #include "src/tint/ast/loop_statement.h"
+#include "src/tint/ast/must_use_attribute.h"
 #include "src/tint/ast/override.h"
 #include "src/tint/ast/return_statement.h"
 #include "src/tint/ast/stage_attribute.h"
@@ -460,8 +461,9 @@ class DependencyScanner {
         }
 
         if (attr->IsAnyOf<ast::BuiltinAttribute, ast::DiagnosticAttribute, ast::InternalAttribute,
-                          ast::InterpolateAttribute, ast::InvariantAttribute, ast::StageAttribute,
+                          ast::InterpolateAttribute, ast::InvariantAttribute, ast::MustUseAttribute,
-                          ast::StrideAttribute, ast::StructMemberOffsetAttribute>()) {
+                          ast::StageAttribute, ast::StrideAttribute,
+                          ast::StructMemberOffsetAttribute>()) {
             return;
         }