[gcc r17-2236] gccrs: add non shorthand field patterns lint

https://gcc.gnu.org/g:e4d8913b6b1d031621f10b5e47ebe00bfd674c6f

commit r17-2236-ge4d8913b6b1d031621f10b5e47ebe00bfd674c6f
Author: Lucas Ly Ba <[email protected]>
Date:   Sat Jun 27 00:39:10 2026 +0200

    gccrs: add non shorthand field patterns lint
    
    gcc/rust/ChangeLog:
    
            * checks/lints/unused/rust-unused-checker.cc (UnusedChecker::visit):
            New.
            * checks/lints/unused/rust-unused-checker.h (UnusedChecker::visit):
            New.
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/non-shorthand-field-patterns_0.rs: New test.
    
    Signed-off-by: Lucas Ly Ba <[email protected]>

Diff:
---
 gcc/rust/checks/lints/unused/rust-unused-checker.cc     | 17 +++++++++++++++++
 gcc/rust/checks/lints/unused/rust-unused-checker.h      |  1 +
 .../rust/compile/non-shorthand-field-patterns_0.rs      | 15 +++++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/gcc/rust/checks/lints/unused/rust-unused-checker.cc b/gcc/rust/checks/lints/unused/rust-unused-checker.cc
index 6fd6c6efe1ca..7d875daef339 100644
--- a/gcc/rust/checks/lints/unused/rust-unused-checker.cc
+++ b/gcc/rust/checks/lints/unused/rust-unused-checker.cc
@@ -198,5 +198,22 @@ UnusedChecker::visit_loop_label (HIR::LoopLabel &label)
 		     "unused label %qs", lifetime.to_string ().c_str ());
 }
 
+void
+UnusedChecker::visit (HIR::StructPatternFieldIdentPat &field)
+{
+  auto &pattern = field.get_pattern ();
+  if (pattern.get_pattern_type () == HIR::Pattern::PatternType::IDENTIFIER)
+    {
+      auto &ident = static_cast<HIR::IdentifierPattern &> (pattern);
+      if (!ident.has_subpattern ()
+	  && ident.get_identifier ().as_string ()
+	       == field.get_identifier ().as_string ())
+	rust_warning_at (field.get_locus (), OPT_Wunused_variable,
+			 "the %qs in this pattern is redundant",
+			 (field.get_identifier ().as_string () + ":").c_str ());
+    }
+  walk (field);
+}
+
 } // namespace Analysis
 } // namespace Rust
diff --git a/gcc/rust/checks/lints/unused/rust-unused-checker.h b/gcc/rust/checks/lints/unused/rust-unused-checker.h
index 58e588022c60..055d49b193e1 100644
--- a/gcc/rust/checks/lints/unused/rust-unused-checker.h
+++ b/gcc/rust/checks/lints/unused/rust-unused-checker.h
@@ -48,6 +48,7 @@ private:
   virtual void visit (HIR::Function &fct) override;
   virtual void visit (HIR::Module &mod) override;
   virtual void visit (HIR::LifetimeParam &lft) override;
+  virtual void visit (HIR::StructPatternFieldIdentPat &field) override;
   virtual void visit_loop_label (HIR::LoopLabel &label) override;
 };
 } // namespace Analysis
diff --git a/gcc/testsuite/rust/compile/non-shorthand-field-patterns_0.rs b/gcc/testsuite/rust/compile/non-shorthand-field-patterns_0.rs
new file mode 100644
index 000000000000..364246e9d557
--- /dev/null
+++ b/gcc/testsuite/rust/compile/non-shorthand-field-patterns_0.rs
@@ -0,0 +1,15 @@
+// { dg-additional-options "-frust-unused-check-2.0" }
+#![feature(no_core)]
+#![no_core]
+
+pub struct Point {
+    pub x: i32,
+    pub y: i32,
+}
+
+pub fn foo(p: Point) -> i32 {
+    match p {
+	Point { x: x, y: _y } => x,
+// { dg-warning "in this pattern is redundant" "" { target *-*-* } .-1 }
+    }
+}