// Copyright (C) 2025 Free Software Foundation, Inc.
// This file is part of GCC.
// GCC is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 3, or (at your option) any later
// version.
// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
// for more details.
// You should have received a copy of the GNU General Public License
// along with GCC; see the file COPYING3. If not see
// .
#include "rust-desugar-for-loops.h"
#include "rust-ast-visitor.h"
#include "rust-ast.h"
#include "rust-hir-map.h"
#include "rust-path.h"
#include "rust-pattern.h"
#include "rust-stmt.h"
#include "rust-expr.h"
#include "rust-ast-builder.h"
namespace Rust {
namespace AST {
DesugarForLoops::DesugarForLoops () {}
void
DesugarForLoops::go (AST::Crate &crate)
{
DefaultASTVisitor::visit (crate);
}
static void
replace_for_loop (std::unique_ptr &for_loop,
std::unique_ptr &&expanded)
{
for_loop = std::move (expanded);
}
MatchArm
DesugarForLoops::DesugarCtx::make_match_arm (std::unique_ptr &&path)
{
auto patterns = std::vector> ();
patterns.emplace_back (std::move (path));
return MatchArm (std::move (patterns), loc);
}
MatchCase
DesugarForLoops::DesugarCtx::make_break_arm ()
{
auto arm = make_match_arm (std::unique_ptr (new PathInExpression (
builder.path_in_expression (LangItem::Kind::OPTION_NONE))));
auto break_expr = std::unique_ptr (
new BreakExpr (Lifetime::error (), nullptr, {}, loc));
return MatchCase (std::move (arm), std::move (break_expr));
}
MatchCase
DesugarForLoops::DesugarCtx::make_continue_arm ()
{
auto val = builder.identifier_pattern (DesugarCtx::continue_pattern_id);
auto patterns = std::vector> ();
patterns.emplace_back (std::move (val));
auto pattern_item = std::unique_ptr (
new TupleStructItemsNoRange (std::move (patterns)));
auto pattern = std::unique_ptr (new TupleStructPattern (
builder.path_in_expression (LangItem::Kind::OPTION_SOME),
std::move (pattern_item)));
auto val_arm = make_match_arm (std::move (pattern));
auto next = builder.identifier (DesugarCtx::next_value_id);
auto assignment = std::unique_ptr (
new AssignmentExpr (std::move (next),
builder.identifier (DesugarCtx::continue_pattern_id),
{}, loc));
return MatchCase (std::move (val_arm), std::move (assignment));
}
std::unique_ptr
DesugarForLoops::DesugarCtx::statementify (std::unique_ptr &&expr)
{
return std::unique_ptr (new ExprStmt (std::move (expr), loc, true));
}
std::unique_ptr
DesugarForLoops::desugar (AST::ForLoopExpr &expr)
{
auto ctx = DesugarCtx (expr.get_locus ());
auto into_iter = std::make_unique (
ctx.builder.path_in_expression (LangItem::Kind::INTOITER_INTOITER));
auto next = std::make_unique (
ctx.builder.path_in_expression (LangItem::Kind::ITERATOR_NEXT));
// IntoIterator::into_iter()
auto into_iter_call
= ctx.builder.call (std::move (into_iter),
expr.get_iterator_expr ().clone_expr ());
// Iterator::next(iter)
auto next_call = ctx.builder.call (
std::move (next),
ctx.builder.ref (ctx.builder.identifier (DesugarCtx::iter_id), true));
// None => break,
auto break_arm = ctx.make_break_arm ();
// Some(val) => __next = val; },
auto continue_arm = ctx.make_continue_arm ();
// match {
//
//
// }
auto match_next
= ctx.builder.match (std::move (next_call),
{std::move (continue_arm), std::move (break_arm)});
// let mut __next;
auto let_next = ctx.builder.let (
ctx.builder.identifier_pattern (DesugarCtx::next_value_id, true));
// let = __next;
auto let_pat
= ctx.builder.let (expr.get_pattern ().clone_pattern (), nullptr,
ctx.builder.identifier (DesugarCtx::next_value_id));
auto loop_stmts = std::vector> ();
loop_stmts.emplace_back (std::move (let_next));
loop_stmts.emplace_back (ctx.statementify (std::move (match_next)));
loop_stmts.emplace_back (std::move (let_pat));
loop_stmts.emplace_back (
ctx.statementify (expr.get_loop_block ().clone_expr ()));
// loop {
// ;
// ;
// ;
//
// ;
// }
auto loop = ctx.builder.loop (std::move (loop_stmts));
auto mut_iter_pattern
= ctx.builder.identifier_pattern (DesugarCtx::iter_id, true);
auto match_iter
= ctx.builder.match (std::move (into_iter_call),
{ctx.builder.match_case (std::move (mut_iter_pattern),
std::move (loop))});
auto let_result
= ctx.builder.let (ctx.builder.identifier_pattern (DesugarCtx::result_id),
nullptr, std::move (match_iter));
auto result_return = ctx.builder.identifier (DesugarCtx::result_id);
return ctx.builder.block (std::move (let_result), std::move (result_return));
}
void
DesugarForLoops::maybe_desugar_expr (std::unique_ptr &expr)
{
if (expr->get_expr_kind () == AST::Expr::Kind::Loop)
{
auto &loop = static_cast (*expr);
if (loop.get_loop_kind () == AST::BaseLoopExpr::Kind::For)
{
auto &for_loop = static_cast (loop);
auto desugared = desugar (for_loop);
replace_for_loop (expr, std::move (desugared));
}
}
}
void
DesugarForLoops::visit (AST::BlockExpr &block)
{
for (auto &stmt : block.get_statements ())
if (stmt->get_stmt_kind () == AST::Stmt::Kind::Expr)
maybe_desugar_expr (static_cast (*stmt).get_expr_ptr ());
if (block.has_tail_expr ())
maybe_desugar_expr (block.get_tail_expr_ptr ());
DefaultASTVisitor::visit (block);
}
} // namespace AST
} // namespace Rust