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// Copyright 2020 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#include <utility>
#include <vector>
#include "src/ast/access.h"
#include "src/ast/decoration.h"
#include "src/ast/expression.h"
#include "src/ast/storage_class.h"
namespace tint {
namespace ast {
// Forward declarations
class BindingDecoration;
class GroupDecoration;
class LocationDecoration;
class Type;
/// VariableBindingPoint holds a group and binding decoration.
struct VariableBindingPoint {
/// The `[[group]]` part of the binding point
const GroupDecoration* group = nullptr;
/// The `[[binding]]` part of the binding point
const BindingDecoration* binding = nullptr;
/// @returns true if the BindingPoint has a valid group and binding
/// decoration.
inline operator bool() const { return group && binding; }
/// A Variable statement.
/// An instance of this class represents one of three constructs in WGSL: "var"
/// declaration, "let" declaration, or formal parameter to a function.
/// 1. A "var" declaration is a name for typed storage. Examples:
/// // Declared outside a function, i.e. at module scope, requires
/// // a storage class.
/// var<workgroup> width : i32; // no initializer
/// var<private> height : i32 = 3; // with initializer
/// // A variable declared inside a function doesn't take a storage class,
/// // and maps to SPIR-V Function storage.
/// var computed_depth : i32;
/// var area : i32 = compute_area(width, height);
/// 2. A "let" declaration is a name for a typed value. Examples:
/// let twice_depth : i32 = width + width; // Must have initializer
/// 3. A formal parameter to a function is a name for a typed value to
/// be passed into a function. Example:
/// fn twice(a: i32) -> i32 { // "a:i32" is the formal parameter
/// return a + a;
/// }
/// From the WGSL draft, about "var"::
/// A variable is a named reference to storage that can contain a value of a
/// particular type.
/// Two types are associated with a variable: its store type (the type of
/// value that may be placed in the referenced storage) and its reference
/// type (the type of the variable itself). If a variable has store type T
/// and storage class S, then its reference type is pointer-to-T-in-S.
/// This class uses the term "type" to refer to:
/// the value type of a "let",
/// the value type of the formal parameter,
/// or the store type of the "var".
/// Setting is_const:
/// - "var" gets false
/// - "let" gets true
/// - formal parameter gets true
/// Setting storage class:
/// - "var" is StorageClass::kNone when using the
/// defaulting syntax for a "var" declared inside a function.
/// - "let" is always StorageClass::kNone.
/// - formal parameter is always StorageClass::kNone.
class Variable : public Castable<Variable, Node> {
/// Create a variable
/// @param program_id the identifier of the program that owns this node
/// @param source the variable source
/// @param sym the variable symbol
/// @param declared_storage_class the declared storage class
/// @param declared_access the declared access control
/// @param type the declared variable type
/// @param is_const true if the variable is const
/// @param constructor the constructor expression
/// @param decorations the variable decorations
Variable(ProgramID program_id,
const Source& source,
const Symbol& sym,
StorageClass declared_storage_class,
Access declared_access,
const ast::Type* type,
bool is_const,
const Expression* constructor,
DecorationList decorations);
/// Move constructor
~Variable() override;
/// @returns the binding point information for the variable
VariableBindingPoint BindingPoint() const;
/// Clones this node and all transitive child nodes using the `CloneContext`
/// `ctx`.
/// @param ctx the clone context
/// @return the newly cloned node
const Variable* Clone(CloneContext* ctx) const override;
/// The variable symbol
const Symbol symbol;
/// The variable type
const ast::Type* const type;
/// True if this is a constant, false otherwise
const bool is_const;
/// The constructor expression or nullptr if none set
const Expression* const constructor;
/// The decorations attached to this variable
const DecorationList decorations;
/// The declared storage class
const StorageClass declared_storage_class;
/// The declared access control
const Access declared_access;
/// A list of variables
using VariableList = std::vector<const Variable*>;
} // namespace ast
} // namespace tint