1 // Copyright (C) 2021-2023 Free Software Foundation, Inc.
2
3 // This file is part of GCC.
4
5 // GCC is free software; you can redistribute it and/or modify it under
6 // the terms of the GNU General Public License as published by the Free
7 // Software Foundation; either version 3, or (at your option) any later
8 // version.
9
10 // GCC is distributed in the hope that it will be useful, but WITHOUT ANY
11 // WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 // FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 // for more details.
14
15 // You should have received a copy of the GNU General Public License
16 // along with GCC; see the file COPYING3. If not see
17 // <http://www.gnu.org/licenses/>.
18
19 #ifndef RUST_HIR_SCAN_DEADCODE
20 #define RUST_HIR_SCAN_DEADCODE
21
22 #include "rust-hir-full-decls.h"
23 #include "rust-hir-map.h"
24 #include "rust-lint-marklive.h"
25 #include "rust-name-resolver.h"
26 #include "rust-diagnostics.h"
27
28 namespace Rust {
29 namespace Analysis {
30
31 // Scan item symbols and warn the symbol if it is not in the live_symbols set.
32 // There are three kinds of item we should handle in this pass.
33 // 1. Function item
34 // 2. The function item in the impl block without trait
35 // 3. StructStruct, e.g., `Struct Foo{one: 1, two: 2}`. Furthermore, the unused
36 // struct fields will be warned too.
37 // 4. TupleStruct, e.g., `Struct Foo(i32, i32)`
38 class ScanDeadcode : public MarkLiveBase
39 {
40 using Rust::Analysis::MarkLiveBase::visit;
41
42 public:
43 static void Scan (HIR::Crate &crate)
44 {
45 std::set<HirId> live_symbols = Analysis::MarkLive::Analysis (crate);
46 ScanDeadcode sdc (live_symbols);
47 for (auto it = crate.items.begin (); it != crate.items.end (); it++)
48 {
49 it->get ()->accept_vis (sdc);
50 }
51 };
52
53 void visit (HIR::Function &function) override
54 {
55 HirId hirId = function.get_mappings ().get_hirid ();
56 if (should_warn (hirId) && !function.get_visibility ().is_public ())
57 {
58 if (mappings->is_impl_item (hirId))
59 {
60 HIR::ImplBlock *implBlock
61 = mappings->lookup_associated_impl (hirId);
62 if (!implBlock->has_trait_ref ())
63 {
64 rust_warning_at (function.get_locus (), 0,
65 "associated function is never used: %<%s%>",
66 function.get_function_name ().c_str ());
67 }
68 }
69 else
70 {
71 rust_warning_at (function.get_locus (), 0,
72 "function is never used: %<%s%>",
73 function.get_function_name ().c_str ());
74 }
75 }
76 }
77
78 void visit (HIR::StructStruct &stct) override
79 {
80 HirId hirId = stct.get_mappings ().get_hirid ();
81 if (should_warn (hirId) && !stct.get_visibility ().is_public ())
82 {
83 bool name_starts_underscore = stct.get_identifier ().at (0) == '_';
84 if (!name_starts_underscore)
85 rust_warning_at (stct.get_locus (), 0,
86 "struct is never constructed: %<%s%>",
87 stct.get_identifier ().c_str ());
88 }
89 else
90 {
91 // only warn the unused fields when in unwarned struct.
92 for (auto &field : stct.get_fields ())
93 {
94 HirId field_hir_id = field.get_mappings ().get_hirid ();
95 if (should_warn (field_hir_id)
96 && !field.get_visibility ().is_public ())
97 {
98 rust_warning_at (field.get_locus (), 0,
99 "field is never read: %<%s%>",
100 field.get_field_name ().c_str ());
101 }
102 }
103 }
104 }
105
106 void visit (HIR::TupleStruct &stct) override
107 {
108 // only warn tuple struct unconstructed, and ignoring unused field
109 HirId hirId = stct.get_mappings ().get_hirid ();
110 if (should_warn (hirId) && !stct.get_visibility ().is_public ())
111 {
112 rust_warning_at (stct.get_locus (), 0,
113 "struct is never constructed: %<%s%>",
114 stct.get_identifier ().c_str ());
115 }
116 }
117
118 void visit (HIR::ImplBlock &blc) override
119 {
120 if (blc.has_impl_items ())
121 {
122 for (auto &implItem : blc.get_impl_items ())
123 {
124 implItem->accept_vis (*this);
125 }
126 }
127 }
128
129 void visit (HIR::Module &mod) override
130 {
131 for (auto &item : mod.get_items ())
132 item->accept_vis (*this);
133 }
134
135 private:
136 std::set<HirId> live_symbols;
137 Resolver::Resolver *resolver;
138 Analysis::Mappings *mappings;
139
140 ScanDeadcode (std::set<HirId> &live_symbols)
141 : live_symbols (live_symbols), resolver (Resolver::Resolver::get ()),
142 mappings (Analysis::Mappings::get ()){};
143
144 bool should_warn (HirId hirId)
145 {
146 // TODO: There are more condition to check if should warn, i.e visibility,
147 // attributes.
148 return live_symbols.find (hirId) == live_symbols.end ();
149 }
150 };
151
152 } // namespace Analysis
153 } // namespace Rust
154
155 #endif