rust-lang / rust-lang/rust-clippy
Simplifying long if-nested-else chains fails
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C-bug
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Description
Summary
When running clippy on long if-nested-else chains, like those produced by c2rust in https://github.com/immunant/c2rust/issues/769, though not the exact code shown in that report, clippy warns with a recommendation to report an issue.
Clippy does make progress, and repeating cargo clippy --fix does result in fixed code.
Reproducer
I tried this code:
cargo clippy --fix
On this lib.rs:
#[no_mangle]
pub unsafe extern "C" fn c_type_name(
mut c: *mut compile_t,
mut name: *const libc::c_char,
) -> *const libc::c_char {
if name == (*c).str_Bool {
return b"bool\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_I8 {
return b"int8_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_I16 {
return b"int16_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_I32 {
return b"int32_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_I64 {
return b"int64_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_I128 {
return b"__int128_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_ILong {
return b"long\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_ISize {
return b"ssize_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_U8 {
return b"char\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_U16 {
return b"uint16_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_U32 {
return b"uint32_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_U64 {
return b"uint64_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_U128 {
return b"__uint128_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_ULong {
return b"unsigned long\0" as *const u8
as *const libc::c_char
} else {
if name == (*c).str_USize {
return b"size_t\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_F32 {
return b"float\0" as *const u8 as *const libc::c_char
} else {
if name == (*c).str_F64 {
return b"double\0" as *const u8 as *const libc::c_char;
}
}
}
}
}
}
}
}
}
}
}
}
}
}
}
}
}
return 0 as *const libc::c_char;
}
#[derive(Copy, Clone)]
#[repr(C)]
pub struct compile_t {
pub filename: *const libc::c_char,
pub str_builtin: *const libc::c_char,
pub str_Bool: *const libc::c_char,
pub str_I8: *const libc::c_char,
pub str_I16: *const libc::c_char,
pub str_I32: *const libc::c_char,
pub str_I64: *const libc::c_char,
pub str_I128: *const libc::c_char,
pub str_ILong: *const libc::c_char,
pub str_ISize: *const libc::c_char,
pub str_U8: *const libc::c_char,
pub str_U16: *const libc::c_char,
pub str_U32: *const libc::c_char,
pub str_U64: *const libc::c_char,
pub str_U128: *const libc::c_char,
pub str_ULong: *const libc::c_char,
pub str_USize: *const libc::c_char,
pub str_F32: *const libc::c_char,
pub str_F64: *const libc::c_char,
pub str_Pointer: *const libc::c_char,
pub str_NullablePointer: *const libc::c_char,
pub str_DoNotOptimise: *const libc::c_char,
pub str_Array: *const libc::c_char,
pub str_String: *const libc::c_char,
pub str_Platform: *const libc::c_char,
pub str_Main: *const libc::c_char,
pub str_Env: *const libc::c_char,
pub str_add: *const libc::c_char,
pub str_sub: *const libc::c_char,
pub str_mul: *const libc::c_char,
pub str_div: *const libc::c_char,
pub str_rem: *const libc::c_char,
pub str_neg: *const libc::c_char,
pub str_add_unsafe: *const libc::c_char,
pub str_sub_unsafe: *const libc::c_char,
pub str_mul_unsafe: *const libc::c_char,
pub str_div_unsafe: *const libc::c_char,
pub str_rem_unsafe: *const libc::c_char,
pub str_neg_unsafe: *const libc::c_char,
pub str_and: *const libc::c_char,
pub str_or: *const libc::c_char,
pub str_xor: *const libc::c_char,
pub str_not: *const libc::c_char,
pub str_shl: *const libc::c_char,
pub str_shr: *const libc::c_char,
pub str_shl_unsafe: *const libc::c_char,
pub str_shr_unsafe: *const libc::c_char,
pub str_eq: *const libc::c_char,
pub str_ne: *const libc::c_char,
pub str_lt: *const libc::c_char,
pub str_le: *const libc::c_char,
pub str_ge: *const libc::c_char,
pub str_gt: *const libc::c_char,
pub str_eq_unsafe: *const libc::c_char,
pub str_ne_unsafe: *const libc::c_char,
pub str_lt_unsafe: *const libc::c_char,
pub str_le_unsafe: *const libc::c_char,
pub str_ge_unsafe: *const libc::c_char,
pub str_gt_unsafe: *const libc::c_char,
pub str_this: *const libc::c_char,
pub str_create: *const libc::c_char,
pub str__create: *const libc::c_char,
pub str__init: *const libc::c_char,
pub str__final: *const libc::c_char,
pub str__event_notify: *const libc::c_char,
pub str__serialise_space: *const libc::c_char,
pub str__serialise: *const libc::c_char,
pub str__deserialise: *const libc::c_char,
}
I expected to see this happen:
clippy writing a fully simplified else-if chain.
Instead, this happened:
Checking repo v0.1.0 (/private/var/folders/bx/x6mc5wkd69sg5_gsd07xsvc00000gn/T/tmp.pICq7eEq/repo)
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 5410...6712 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 5170...6758 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 4942...6800 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 4726...6838 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 4527...6872 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 4334...6902 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 4156...6928 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 3985...6950 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 3830...6968 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 3687...6982 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 3556...6992 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
warning: error applying suggestions to `src/lib.rs`
The full error message was:
> Could not replace range 3439...6998 in file -- maybe parts of it were already replaced?
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
Fixed src/lib.rs (6 fixes)
warning: this `else { if .. }` block can be collapsed
--> src/lib.rs:97:12
|
97 | } else {
| ____________^
98 | | if name == (*c).str_I8 {
99 | | return b"int8_t\0" as *const u8 as *const libc::c_char
100 | | } else {
... |
153 | | }
154 | | }
| |_____^
|
= note: `#[warn(clippy::collapsible_else_if)]` on by default
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#collapsible_else_if
help: collapse nested if block
|
97 ~ } else if name == (*c).str_I8 {
98 + return b"int8_t\0" as *const u8 as *const libc::c_char
99 + } else {
100 + if name == (*c).str_I16 {
101 + return b"int16_t\0" as *const u8 as *const libc::c_char
102 + } else {
103 + if name == (*c).str_I32 {
104 + return b"int32_t\0" as *const u8 as *const libc::c_char
105 + } else {
106 + if name == (*c).str_I64 {
107 + return b"int64_t\0" as *const u8 as *const libc::c_char
108 + } else {
109 + if name == (*c).str_I128 {
110 + return b"__int128_t\0" as *const u8 as *const libc::c_char
111 + } else {
112 + if name == (*c).str_ILong {
113 + return b"long\0" as *const u8 as *const libc::c_char
114 + } else {
115 + if name == (*c).str_ISize {
116 + return b"ssize_t\0" as *const u8 as *const libc::c_char
117 + } else {
118 + if name == (*c).str_U8 {
119 + return b"char\0" as *const u8 as *const libc::c_char
120 + } else {
121 + if name == (*c).str_U16 {
122 + return b"uint16_t\0" as *const u8 as *const libc::c_char
123 + } else {
124 + if name == (*c).str_U32 {
125 + return b"uint32_t\0" as *const u8 as *const libc::c_char
126 + } else {
127 + if name == (*c).str_U64 {
128 + return b"uint64_t\0" as *const u8 as *const libc::c_char
129 + } else {
130 + if name == (*c).str_U128 {
131 + return b"__uint128_t\0" as *const u8 as *const libc::c_char
132 + } else if name == (*c).str_ULong {
133 + return b"unsigned long\0" as *const u8
134 + as *const libc::c_char
135 + } else if name == (*c).str_USize {
136 + return b"size_t\0" as *const u8 as *const libc::c_char
137 + } else if name == (*c).str_F32 {
138 + return b"float\0" as *const u8 as *const libc::c_char
139 + } else if name == (*c).str_F64 {
140 + return b"double\0" as *const u8 as *const libc::c_char;
141 + }
142 + }
143 + }
144 + }
145 + }
146 + }
147 + }
148 + }
149 + }
150 + }
151 + }
152 + }
|
[… Repeated several times …]
warning: unsafe function's docs miss `# Safety` section
--> src/lib.rs:91:1
|
91 | / pub unsafe extern "C" fn c_type_name(
92 | | mut c: *mut compile_t,
93 | | mut name: *const libc::c_char,
94 | | ) -> *const libc::c_char {
... |
147 | | std::ptr::null::<libc::c_char>()
148 | | }
| |_^
|
= note: `#[warn(clippy::missing_safety_doc)]` on by default
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#missing_safety_doc
warning: `repo` (lib test) generated 9 warnings
Finished dev [unoptimized + debuginfo] target(s) in 2.47s
Version
rustc 1.65.0 (897e37553 2022-11-02)
binary: rustc
commit-hash: 897e37553bba8b42751c67658967889d11ecd120
commit-date: 2022-11-02
host: x86_64-apple-darwin
release: 1.65.0
LLVM version: 15.0.0
Additional Labels
No response
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the problem with cargo clippy --fix on the provided src/lib.rs nested if/else chain and inspect the suggestions that produce overlapping replacement ranges. Trace the Clippy lint and suggestion application path responsible for the simplification; done means the chain is fully simplified without replacement warnings.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100