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Implement unused variable checker on HIR.
gcc/rust/ChangeLog: * Make-lang.in: New file. * checks/lints/unused-var/rust-unused-var-checker.cc (UnusedVarChecker): Implement unused variable checker. * checks/lints/unused-var/rust-unused-var-checker.h (UnusedVarChecker): Implement unused variable checker. * checks/lints/unused-var/rust-unused-var-collector.cc (UnusedVarCollector): Implement unused variable collector. * checks/lints/unused-var/rust-unused-var-collector.h (UnusedVarCollector): Implement unused variable collector. * checks/lints/unused-var/rust-unused-var-context.cc (UnusedVarContext): Implement unused variable context. * checks/lints/unused-var/rust-unused-var-context.h (UnusedVarContext): Implement unused variable context. Signed-off-by: Ryutaro Okada <[email protected]>
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‎gcc/rust/Make-lang.in

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@@ -208,6 +208,9 @@ GRS_OBJS = \
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rust/rust-const-checker.o \
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rust/rust-lint-marklive.o \
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rust/rust-lint-unused-var.o \
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rust/rust-unused-var-checker.o \
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rust/rust-unused-var-collector.o \
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rust/rust-unused-var-context.o \
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rust/rust-readonly-check.o \
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rust/rust-readonly-check2.o \
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rust/rust-hir-type-check-path.o \
@@ -441,6 +444,7 @@ RUST_INCLUDES = -I $(srcdir)/rust \
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-I $(srcdir)/rust/typecheck \
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-I $(srcdir)/rust/checks/lints \
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-I $(srcdir)/rust/checks/errors \
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-I $(srcdir)/rust/checks/lints/unused-var \
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-I $(srcdir)/rust/checks/errors/privacy \
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-I $(srcdir)/rust/checks/errors/borrowck \
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-I $(srcdir)/rust/util \
@@ -510,6 +514,11 @@ rust/%.o: rust/checks/lints/%.cc
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$(COMPILE) $(RUST_CXXFLAGS) $(RUST_INCLUDES) $<
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$(POSTCOMPILE)
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# build unused variable checking pass files in rust folder
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rust/%.o: rust/checks/lints/unused-var/%.cc
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$(COMPILE) $(RUST_CXXFLAGS) $(RUST_INCLUDES) $<
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$(POSTCOMPILE)
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# build rust/checks/errors files in rust folder
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rust/%.o: rust/checks/errors/%.cc
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$(COMPILE) $(RUST_CXXFLAGS) $(RUST_INCLUDES) $<

‎gcc/rust/checks/lints/unused-var/rust-unused-var-checker.cc

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// Copyright (C) 2025 Free Software Foundation, Inc.
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// This file is part of GCC.
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// GCC is free software; you can redistribute it and/or modify it under
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// the terms of the GNU General Public License as published by the Free
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// Software Foundation; either version 3, or (at your option) any later
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// version.
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// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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// You should have received a copy of the GNU General Public License
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// along with GCC; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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#include "rust-unused-var-checker.h"
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#include "rust-hir-item.h"
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#include "options.h"
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namespace Rust {
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namespace Analysis {
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UnusedVarChecker::UnusedVarChecker ()
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: nr_context (
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Resolver2_0::ImmutableNameResolutionContext::get ().resolver ()),
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mappings (Analysis::Mappings::get ()),
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unused_var_context (*UnusedVarContext::get ())
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{}
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void
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UnusedVarChecker::go (HIR::Crate &crate)
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{
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UnusedVarCollector ().go (crate);
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for (auto &item : crate.get_items ())
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item->accept_vis (*this);
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}
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void
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UnusedVarChecker::visit (HIR::LetStmt &stmt)
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{
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HIR::Pattern &pattern = stmt.get_pattern ();
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check_variable (pattern);
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walk (stmt);
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}
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void
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UnusedVarChecker::visit_function_param (HIR::FunctionParam &param)
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{
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check_variable (param.get_param_name ());
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}
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void
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UnusedVarChecker::visit (HIR::ConstantItem &item)
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{
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std::string var_name = item.get_identifier ().as_string ();
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bool starts_with_under_score = var_name.compare (0, 1, "_") == 0;
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auto id = item.get_mappings ().get_hirid ();
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if (!unused_var_context.is_variable_used (id) && !starts_with_under_score)
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rust_warning_at (item.get_locus (), OPT_Wunused_variable,
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"unused name '%s'",
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item.get_identifier ().as_string ().c_str ());
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}
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void
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UnusedVarChecker::visit (HIR::StaticItem &item)
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{
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std::string var_name = item.get_identifier ().as_string ();
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bool starts_with_under_score = var_name.compare (0, 1, "_") == 0;
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auto id = item.get_mappings ().get_hirid ();
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if (!unused_var_context.is_variable_used (id) && !starts_with_under_score)
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rust_warning_at (item.get_locus (), OPT_Wunused_variable,
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"unused name '%s'",
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item.get_identifier ().as_string ().c_str ());
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}
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void
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UnusedVarChecker::visit (HIR::TraitItemFunc &item)
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{
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// TODO: check trait item functions if they are not derived.
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}
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void
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UnusedVarChecker::check_variable (HIR::Pattern &pattern)
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{
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switch (pattern.get_pattern_type ())
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{
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case HIR::Pattern::PatternType::IDENTIFIER:
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check_variable_identifier (
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static_cast<HIR::IdentifierPattern &> (pattern));
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break;
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case HIR::Pattern::PatternType::TUPLE:
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check_variable_tuple (static_cast<HIR::TuplePattern &> (pattern));
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break;
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default:
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break;
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}
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}
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void
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UnusedVarChecker::check_variable_identifier (HIR::IdentifierPattern &pattern)
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{
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std::string var_name = pattern.get_identifier ().as_string ();
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bool starts_with_under_score = var_name.compare (0, 1, "_") == 0;
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auto id = pattern.get_mappings ().get_hirid ();
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if (!unused_var_context.is_variable_used (id) && var_name != "self"
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&& !starts_with_under_score)
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rust_warning_at (pattern.get_locus (), OPT_Wunused_variable,
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"unused name '%s'",
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pattern.get_identifier ().as_string ().c_str ());
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}
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void
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UnusedVarChecker::check_variable_tuple (HIR::TuplePattern &pattern)
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{
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switch (pattern.get_items ().get_item_type ())
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{
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case HIR::TupleItems::ItemType::MULTIPLE:
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{
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auto items = static_cast<HIR::TuplePatternItemsMultiple &> (
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pattern.get_items ());
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for (auto &item : items.get_patterns ())
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check_variable (*item);
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}
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break;
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default:
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break;
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}
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}
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} // namespace Analysis
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} // namespace Rust

‎gcc/rust/checks/lints/unused-var/rust-unused-var-checker.h

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// Copyright (C) 2025 Free Software Foundation, Inc.
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// This file is part of GCC.
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// GCC is free software; you can redistribute it and/or modify it under
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// the terms of the GNU General Public License as published by the Free
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// Software Foundation; either version 3, or (at your option) any later
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// version.
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// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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// You should have received a copy of the GNU General Public License
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// along with GCC; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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#include "rust-hir-item.h"
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#include "rust-hir-visitor.h"
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#include "rust-immutable-name-resolution-context.h"
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#include "rust-unused-var-collector.h"
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namespace Rust {
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namespace Analysis {
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class UnusedVarChecker : public HIR::DefaultHIRVisitor
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{
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public:
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UnusedVarChecker ();
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void go (HIR::Crate &crate);
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private:
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const Resolver2_0::NameResolutionContext &nr_context;
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Analysis::Mappings &mappings;
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UnusedVarContext &unused_var_context;
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using HIR::DefaultHIRVisitor::visit;
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virtual void visit (HIR::LetStmt &stmt) override;
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virtual void visit_function_param (HIR::FunctionParam &param) override;
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virtual void visit (HIR::TraitItemFunc &decl) override;
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virtual void visit (HIR::ConstantItem &item) override;
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virtual void visit (HIR::StaticItem &item) override;
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void check_variable_identifier (HIR::IdentifierPattern &identifier);
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void check_variable_tuple (HIR::TuplePattern &pattern);
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void check_variable (HIR::Pattern &pattern);
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};
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} // namespace Analysis
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} // namespace Rust

‎gcc/rust/checks/lints/unused-var/rust-unused-var-collector.cc

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// Copyright (C) 2025 Free Software Foundation, Inc.
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// This file is part of GCC.
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// GCC is free software; you can redistribute it and/or modify it under
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// the terms of the GNU General Public License as published by the Free
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// Software Foundation; either version 3, or (at your option) any later
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// version.
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// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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// You should have received a copy of the GNU General Public License
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// along with GCC; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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#include "rust-unused-var-collector.h"
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#include "rust-hir-full-decls.h"
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#include "rust-hir-item.h"
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#include "rust-hir-path.h"
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#include "rust-immutable-name-resolution-context.h"
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namespace Rust {
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namespace Analysis {
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UnusedVarCollector::UnusedVarCollector ()
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: nr_context (
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Resolver2_0::ImmutableNameResolutionContext::get ().resolver ()),
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mappings (Analysis::Mappings::get ()),
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unused_var_context (*UnusedVarContext::get ())
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{}
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void
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UnusedVarCollector::go (HIR::Crate &crate)
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{
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for (auto &item : crate.get_items ())
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item->accept_vis (*this);
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}
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void
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UnusedVarCollector::visit (HIR::LetStmt &stmt)
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{
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HIR::Pattern &pattern = stmt.get_pattern ();
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collect_variable (pattern);
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walk (stmt);
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}
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void
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UnusedVarCollector::visit (HIR::ConstantItem &item)
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{
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unused_var_context.add_variable (item.get_mappings ().get_hirid ());
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walk (item);
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}
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void
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UnusedVarCollector::visit (HIR::StaticItem &item)
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{
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unused_var_context.add_variable (item.get_mappings ().get_hirid ());
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walk (item);
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}
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void
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UnusedVarCollector::visit_function_param (HIR::FunctionParam &param)
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{
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collect_variable (param.get_param_name ());
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}
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void
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UnusedVarCollector::visit_closure_param (HIR::ClosureParam &param)
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{
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collect_variable (param.get_pattern ());
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}
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void
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UnusedVarCollector::collect_variable (HIR::Pattern &pattern)
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{
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switch (pattern.get_pattern_type ())
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{
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case HIR::Pattern::PatternType::IDENTIFIER:
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{
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auto &identifier = static_cast<HIR::IdentifierPattern &> (pattern);
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auto id = identifier.get_mappings ().get_hirid ();
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unused_var_context.add_variable (id);
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}
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break;
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case HIR::Pattern::PatternType::TUPLE:
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{
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collect_variable_tuple (static_cast<HIR::TuplePattern &> (pattern));
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}
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break;
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default:
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break;
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}
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}
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void
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UnusedVarCollector::collect_variable_tuple (HIR::TuplePattern &pattern)
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{
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switch (pattern.get_items ().get_item_type ())
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{
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case HIR::TuplePatternItems::ItemType::MULTIPLE:
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{
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auto &items = static_cast<HIR::TuplePatternItemsMultiple &> (
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pattern.get_items ());
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for (auto &sub : items.get_patterns ())
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collect_variable (*sub);
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}
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break;
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default:
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break;
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}
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}
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void
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UnusedVarCollector::visit (HIR::PathInExpression &expr)
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{
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mark_path_used (expr);
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}
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void
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UnusedVarCollector::visit (HIR::QualifiedPathInExpression &expr)
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{
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mark_path_used (expr);
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}
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void
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UnusedVarCollector::visit (HIR::StructExprFieldIdentifier &ident)
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{
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mark_path_used (ident);
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}
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} // namespace Analysis
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} // namespace Rust

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