https://gcc.gnu.org/g:bdb6f7f2c065c878f84e9d52c74962cb2d40fc2c
commit r16-2978-gbdb6f7f2c065c878f84e9d52c74962cb2d40fc2c
Author: Arthur Cohen <arthur.co...@embecosm.com>
Date: Tue Jul 22 17:16:02 2025 +0200
gccrs: desugar: Add base for desugaring while-let loops
gcc/rust/ChangeLog:
* Make-lang.in:
* ast/rust-expression-yeast.cc (ExpressionYeast::dispatch_loops):
Call DesugarWhileLet.
* ast/rust-desugar-while-let.cc: New file.
* ast/rust-desugar-while-let.h: New file.
gcc/testsuite/ChangeLog:
* rust/compile/while_let1.rs: New test.
Diff:
---
gcc/rust/Make-lang.in | 1 +
gcc/rust/ast/rust-desugar-while-let.cc | 104 +++++++++++++++++++++++++++++
gcc/rust/ast/rust-desugar-while-let.h | 71 ++++++++++++++++++++
gcc/rust/ast/rust-expression-yeast.cc | 6 +-
gcc/testsuite/rust/compile/while_let1.rs | 109 +++++++++++++++++++++++++++++++
5 files changed, 289 insertions(+), 2 deletions(-)
diff --git a/gcc/rust/Make-lang.in b/gcc/rust/Make-lang.in
index 98590d20b8ce..1c58bc88e9cd 100644
--- a/gcc/rust/Make-lang.in
+++ b/gcc/rust/Make-lang.in
@@ -245,6 +245,7 @@ GRS_OBJS = \
rust/rust-collect-lang-items.o \
rust/rust-expression-yeast.o \
rust/rust-desugar-for-loops.o \
+ rust/rust-desugar-while-let.o \
rust/rust-desugar-question-mark.o \
rust/rust-desugar-apit.o \
rust/rust-desugar-try-block.o \
diff --git a/gcc/rust/ast/rust-desugar-while-let.cc
b/gcc/rust/ast/rust-desugar-while-let.cc
new file mode 100644
index 000000000000..5eadc5908fd0
--- /dev/null
+++ b/gcc/rust/ast/rust-desugar-while-let.cc
@@ -0,0 +1,104 @@
+// 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
+// <http://www.gnu.org/licenses/>.
+
+#include "rust-desugar-while-let.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 {
+
+DesugarWhileLet::DesugarWhileLet () {}
+
+MatchCase
+DesugarWhileLet::DesugarCtx::make_break_arm ()
+{
+ auto arm = builder.match_arm (builder.wildcard ());
+
+ auto break_expr
+ = std::unique_ptr<Expr> (new BreakExpr (tl::nullopt, nullptr, {}, loc));
+
+ return MatchCase (std::move (arm), std::move (break_expr));
+}
+
+MatchCase
+DesugarWhileLet::DesugarCtx::make_continue_arm (
+ std::unique_ptr<Pattern> &&pattern, std::unique_ptr<BlockExpr> &&body)
+{
+ auto arm = builder.match_arm (std::move (pattern));
+
+ return MatchCase (std::move (arm), std::move (body));
+}
+
+std::unique_ptr<Expr>
+DesugarWhileLet::desugar (WhileLetLoopExpr &expr)
+{
+ rust_assert (expr.get_patterns ().size () == 1);
+
+ auto pattern = expr.get_patterns ()[0]->clone_pattern ();
+ auto body = expr.get_loop_block ().clone_block_expr ();
+ auto scrutinee = expr.get_scrutinee_expr ().clone_expr ();
+
+ auto ctx = DesugarCtx (expr.get_locus ());
+
+ // _ => break,
+ auto break_arm = ctx.make_break_arm ();
+
+ // <pattern> => <body>,
+ auto continue_arm
+ = ctx.make_continue_arm (std::move (pattern), std::move (body));
+
+ // match <scrutinee> {
+ // <continue_arm>
+ // <break_arm>
+ // }
+ auto match_expr
+ = ctx.builder.match (std::move (scrutinee),
+ {std::move (continue_arm), std::move (break_arm)});
+
+ auto loop_stmts = std::vector<std::unique_ptr<Stmt>> ();
+ loop_stmts.emplace_back (ctx.builder.statementify (std::move (match_expr)));
+
+ // loop {
+ // <match_expr>
+ // }
+ return ctx.builder.loop (std::move (loop_stmts));
+}
+
+void
+DesugarWhileLet::go (std::unique_ptr<Expr> &ptr)
+{
+ rust_assert (ptr->get_expr_kind () == Expr::Kind::Loop);
+
+ auto &loop = static_cast<BaseLoopExpr &> (*ptr);
+
+ rust_assert (loop.get_loop_kind () == BaseLoopExpr::Kind::WhileLet);
+
+ auto &while_let = static_cast<WhileLetLoopExpr &> (loop);
+ auto desugared = DesugarWhileLet ().desugar (while_let);
+
+ ptr = std::move (desugared);
+}
+
+} // namespace AST
+} // namespace Rust
diff --git a/gcc/rust/ast/rust-desugar-while-let.h
b/gcc/rust/ast/rust-desugar-while-let.h
new file mode 100644
index 000000000000..60e06934e492
--- /dev/null
+++ b/gcc/rust/ast/rust-desugar-while-let.h
@@ -0,0 +1,71 @@
+// 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
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_DESUGAR_WHILE_LET_H
+#define RUST_DESUGAR_WHILE_LET_H
+
+#include "rust-ast-builder.h"
+#include "rust-expr.h"
+
+namespace Rust {
+namespace AST {
+
+// Desugar while-let into a set of other AST nodes. The desugar is of the
+// following form:
+//
+// ```
+// whilet let <pat> = <expr> <body>
+// ```
+//
+// becomes:
+//
+// ```
+// loop {
+// match <expr> {
+// <pat> => <body>,
+// _ => break
+// }
+// }
+// ```
+class DesugarWhileLet
+{
+public:
+ static void go (std::unique_ptr<Expr> &ptr);
+
+private:
+ DesugarWhileLet ();
+
+ struct DesugarCtx
+ {
+ DesugarCtx (location_t loc) : builder (Builder (loc)), loc (loc) {}
+
+ Builder builder;
+ location_t loc;
+
+ MatchCase make_break_arm ();
+ MatchCase make_continue_arm (std::unique_ptr<Pattern> &&pattern,
+ std::unique_ptr<BlockExpr> &&body);
+ };
+
+ std::unique_ptr<Expr> desugar (WhileLetLoopExpr &expr);
+};
+
+} // namespace AST
+} // namespace Rust
+
+#endif // ! RUST_DESUGAR_WHILE_LET_H
diff --git a/gcc/rust/ast/rust-expression-yeast.cc
b/gcc/rust/ast/rust-expression-yeast.cc
index e8cf6d5af8e4..9f6a62ff37c2 100644
--- a/gcc/rust/ast/rust-expression-yeast.cc
+++ b/gcc/rust/ast/rust-expression-yeast.cc
@@ -22,6 +22,7 @@
#include "rust-desugar-try-block.h"
#include "rust-desugar-for-loops.h"
#include "rust-ast-full.h"
+#include "rust-desugar-while-let.h"
#include "rust-expr.h"
#include "rust-stmt.h"
@@ -44,9 +45,10 @@ ExpressionYeast::dispatch_loops (std::unique_ptr<Expr>
&loop_expr)
case BaseLoopExpr::Kind::For:
DesugarForLoops::go (loop_expr);
break;
- case BaseLoopExpr::Kind::Loop:
- case BaseLoopExpr::Kind::While:
case BaseLoopExpr::Kind::WhileLet:
+ DesugarWhileLet::go (loop_expr);
+ break;
+ default:
break;
}
}
diff --git a/gcc/testsuite/rust/compile/while_let1.rs
b/gcc/testsuite/rust/compile/while_let1.rs
new file mode 100644
index 000000000000..a3fa3053226a
--- /dev/null
+++ b/gcc/testsuite/rust/compile/while_let1.rs
@@ -0,0 +1,109 @@
+// use self::Ordering::*;
+// use Ordering::*;
+
+// enum Ordering {
+// A,
+// B,
+// }
+
+// fn foo(_: Ordering) {}
+
+// fn main() {
+// let a = A;
+
+// foo(a);
+// foo(B);
+// }
+
+#[lang = "sized"]
+trait Sized {}
+
+enum Result<T, E> {
+ Ok(T),
+ Err(E),
+}
+
+pub trait Try {
+ /// The type of this value when viewed as successful.
+ #[unstable(feature = "try_trait", issue = "42327")]
+ type Ok;
+ /// The type of this value when viewed as failed.
+ #[unstable(feature = "try_trait", issue = "42327")]
+ type Error;
+
+ /// Applies the "?" operator. A return of `Ok(t)` means that the
+ /// execution should continue normally, and the result of `?` is the
+ /// value `t`. A return of `Err(e)` means that execution should branch
+ /// to the innermost enclosing `catch`, or return from the function.
+ ///
+ /// If an `Err(e)` result is returned, the value `e` will be "wrapped"
+ /// in the return type of the enclosing scope (which must itself implement
+ /// `Try`). Specifically, the value `X::from_error(From::from(e))`
+ /// is returned, where `X` is the return type of the enclosing function.
+ #[lang = "into_result"]
+ #[unstable(feature = "try_trait", issue = "42327")]
+ fn into_result(self) -> Result<Self::Ok, Self::Error>;
+
+ /// Wrap an error value to construct the composite result. For example,
+ /// `Result::Err(x)` and `Result::from_error(x)` are equivalent.
+ #[lang = "from_error"]
+ #[unstable(feature = "try_trait", issue = "42327")]
+ fn from_error(v: Self::Error) -> Self;
+
+ /// Wrap an OK value to construct the composite result. For example,
+ /// `Result::Ok(x)` and `Result::from_ok(x)` are equivalent.
+ #[lang = "from_ok"]
+ #[unstable(feature = "try_trait", issue = "42327")]
+ fn from_ok(v: Self::Ok) -> Self;
+}
+
+pub struct NoneError;
+
+pub enum Option<T> {
+ /// No value
+ None,
+ /// Some value `T`
+ Some(T),
+}
+
+impl<T> Option<T> {
+ pub fn ok_or<E>(self, err: E) -> Result<T, E> {
+ match self {
+ Some(ok) => Result::Ok(ok),
+ None => Result::Err(err),
+ }
+ }
+}
+
+use Option::*;
+
+#[unstable(feature = "try_trait", issue = "42327")]
+impl<T> Try for Option<T> {
+ type Ok = T;
+ type Error = NoneError;
+
+ #[inline]
+ fn into_result(self) -> Result<T, NoneError> {
+ self.ok_or(NoneError)
+ }
+
+ #[inline]
+ fn from_ok(v: T) -> Self {
+ Some(v)
+ }
+
+ #[inline]
+ fn from_error(_: NoneError) -> Self {
+ None
+ }
+}
+
+fn foo() -> Option<i32> {
+ Option::Some(15)
+}
+
+fn main() {
+ // let _: Option<i32> = try { 15i32 };
+
+ while let Option::Some(15) = foo() {}
+}
