tint/sem: Add FunctionExpression

Will be generated for expressions that resolve to functions.

Bug: tint:1810
Change-Id: I334729c9499be7b1c4ab229c1845a4d5f06fa107
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/119701
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>

src/tint/BUILD.gn

@@ -361,6 +361,7 @@ libtint_source_set("libtint_syntax_tree_src") {
     "sem/expression.h",
     "sem/for_loop_statement.h",
     "sem/function.h",
+    "sem/function_expression.h",
     "sem/if_statement.h",
     "sem/index_accessor_expression.h",
     "sem/info.h",
@@ -741,6 +742,8 @@ libtint_source_set("libtint_sem_src") {
     "sem/for_loop_statement.h",
     "sem/function.cc",
     "sem/function.h",
+    "sem/function_expression.cc",
+    "sem/function_expression.h",
     "sem/if_statement.cc",
     "sem/if_statement.h",
     "sem/index_accessor_expression.cc",

src/tint/CMakeLists.txt

@@ -316,6 +316,8 @@ list(APPEND TINT_LIB_SRCS
   sem/expression.h
   sem/for_loop_statement.cc
   sem/for_loop_statement.h
+  sem/function_expression.cc
+  sem/function_expression.h
   sem/function.cc
   sem/if_statement.cc
   sem/if_statement.h

src/tint/sem/function_expression.cc

@@ -0,0 +1,28 @@
+// 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/sem/function_expression.h"
+
+TINT_INSTANTIATE_TYPEINFO(tint::sem::FunctionExpression);
+
+namespace tint::sem {
+
+FunctionExpression::FunctionExpression(const ast::Expression* declaration,
+                                       const Statement* statement,
+                                       const sem::Function* function)
+    : Base(declaration, statement), function_(function) {}
+
+FunctionExpression::~FunctionExpression() = default;
+
+}  // namespace tint::sem

src/tint/sem/function_expression.h

@@ -0,0 +1,51 @@
+// 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_SEM_FUNCTION_EXPRESSION_H_
+#define SRC_TINT_SEM_FUNCTION_EXPRESSION_H_
+
+#include "src/tint/sem/expression.h"
+
+// Forward declarations
+namespace tint::sem {
+class Function;
+}  // namespace tint::sem
+
+namespace tint::sem {
+
+/// FunctionExpression holds the semantic information for expression nodes that resolve to
+/// functions.
+class FunctionExpression : public Castable<FunctionExpression, Expression> {
+  public:
+    /// Constructor
+    /// @param declaration the AST node
+    /// @param statement the statement that owns this expression
+    /// @param function the function that the expression resolved to
+    FunctionExpression(const ast::Expression* declaration,
+                       const Statement* statement,
+                       const sem::Function* function);
+
+    /// Destructor
+    ~FunctionExpression() override;
+
+    /// @return the function that the expression resolved to
+    const sem::Function* Function() const { return function_; }
+
+  private:
+    sem::Function const* const function_;
+};
+
+}  // namespace tint::sem
+
+#endif  // SRC_TINT_SEM_FUNCTION_EXPRESSION_H_