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Auto merge of #3808 - mikerite:useless-format-suggestions, r=oli-obk 

Fix `useless_format` suggestions
This commit is contained in:
bors 2019-02-25 16:21:26 +00:00
parent 2141ebf695 0182a6640e
commit 50d9473856
5 changed files with 107 additions and 55 deletions
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2
ci/base-tests.sh
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@ -59,7 +59,7 @@ rustup override set nightly
# avoid loop spam and allow cmds with exit status != 0
set +ex
for file in `find tests -not -path "tests/ui/format.rs" -not -path "tests/ui/formatting.rs" -not -path "tests/ui/empty_line_after_outer_attribute.rs" -not -path "tests/ui/double_parens.rs" -not -path "tests/ui/doc.rs" -not -path "tests/ui/unused_unit.rs" | grep "\.rs$"` ; do
for file in `find tests -not -path "tests/ui/formatting.rs" -not -path "tests/ui/empty_line_after_outer_attribute.rs" -not -path "tests/ui/double_parens.rs" -not -path "tests/ui/doc.rs" -not -path "tests/ui/unused_unit.rs" | grep "\.rs$"` ; do
rustfmt ${file} --check
if [ $? -ne 0 ]; then
echo "${file} needs reformatting!"

40
clippy_lints/src/format.rs
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@ -5,11 +5,12 @@ use crate::utils::{
};
use if_chain::if_chain;
use rustc::hir::*;
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use rustc::lint::{LateContext, LateLintPass, LintArray, LintContext, LintPass};
use rustc::ty;
use rustc::{declare_tool_lint, lint_array};
use rustc_errors::Applicability;
use syntax::ast::LitKind;
use syntax::source_map::Span;
/// **What it does:** Checks for the use of `format!("string literal with no
/// argument")` and `format!("{}", foo)` where `foo` is a string.
@ -82,14 +83,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
}
};
span_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
db.span_suggestion(
expr.span,
message,
sugg,
Applicability::MachineApplicable,
);
});
span_useless_format(cx, span, message, sugg);
}
}
},
@ -98,14 +92,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
if let ExprKind::Tup(ref tup) = matchee.node {
if tup.is_empty() {
let sugg = format!("{}.to_string()", snippet(cx, expr.span, "<expr>").into_owned());
span_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
db.span_suggestion(
span,
"consider using .to_string()",
sugg,
Applicability::MachineApplicable, // snippet
);
});
span_useless_format(cx, span, "consider using .to_string()", sugg);
}
}
},
@ -115,6 +102,25 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
}
}
fn span_useless_format<'a, 'tcx: 'a, T: LintContext<'tcx>>(cx: &'a T, span: Span, help: &str, mut sugg: String) {
let to_replace = span.source_callsite();
// The callsite span contains the statement semicolon for some reason.
let snippet = snippet(cx, to_replace, "..");
if snippet.ends_with(';') {
sugg.push(';');
}
span_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
db.span_suggestion(
to_replace,
help,
sugg,
Applicability::MachineApplicable, // snippet
);
});
}
/// Checks if the expressions matches `&[""]`
fn check_single_piece(expr: &Expr) -> bool {
if_chain! {

60
tests/ui/format.fixed Normal file
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@ -0,0 +1,60 @@
// run-rustfix
#![allow(clippy::print_literal)]
#![warn(clippy::useless_format)]
struct Foo(pub String);
macro_rules! foo {
($($t:tt)*) => (Foo(format!($($t)*)))
}
fn main() {
"foo".to_string();
"foo".to_string();
format!("{:?}", "foo"); // don't warn about debug
format!("{:8}", "foo");
format!("{:width$}", "foo", width = 8);
"foo".to_string(); // warn when the format makes no difference
"foo".to_string(); // warn when the format makes no difference
format!("foo {}", "bar");
format!("{} bar", "foo");
let arg: String = "".to_owned();
arg.to_string();
format!("{:?}", arg); // don't warn about debug
format!("{:8}", arg);
format!("{:width$}", arg, width = 8);
arg.to_string(); // warn when the format makes no difference
arg.to_string(); // warn when the format makes no difference
format!("foo {}", arg);
format!("{} bar", arg);
// we don’t want to warn for non-string args, see #697
format!("{}", 42);
format!("{:?}", 42);
format!("{:+}", 42);
format!("foo {}", 42);
format!("{} bar", 42);
// we only want to warn about `format!` itself
println!("foo");
println!("{}", "foo");
println!("foo {}", "foo");
println!("{}", 42);
println!("foo {}", 42);
// A format! inside a macro should not trigger a warning
foo!("should not warn");
// precision on string means slicing without panicking on size:
format!("{:.1}", "foo"); // could be "foo"[..1]
format!("{:.10}", "foo"); // could not be "foo"[..10]
format!("{:.prec$}", "foo", prec = 1);
format!("{:.prec$}", "foo", prec = 10);
42.to_string();
let x = std::path::PathBuf::from("/bar/foo/qux");
x.display().to_string();
}

2
tests/ui/format.rs
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@ -1,3 +1,5 @@
// run-rustfix
#![allow(clippy::print_literal)]
#![warn(clippy::useless_format)]

58
tests/ui/format.stderr
View File

@ -1,74 +1,58 @@
error: useless use of `format!`
--> $DIR/format.rs:11:5
--> $DIR/format.rs:13:5
|
LL | format!("foo");
| ^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string()`
| ^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string();`
|
= note: `-D clippy::useless-format` implied by `-D warnings`
error: useless use of `format!`
--> $DIR/format.rs:13:5
--> $DIR/format.rs:15:5
|
LL | format!("{}", "foo");
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string()`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string();`
error: useless use of `format!`
--> $DIR/format.rs:17:5
--> $DIR/format.rs:19:5
|
LL | format!("{:+}", "foo"); // warn when the format makes no difference
| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string()`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string();`
error: useless use of `format!`
--> $DIR/format.rs:18:5
--> $DIR/format.rs:20:5
|
LL | format!("{:<}", "foo"); // warn when the format makes no difference
| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string()`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string();`
error: useless use of `format!`
--> $DIR/format.rs:23:5
--> $DIR/format.rs:25:5
|
LL | format!("{}", arg);
| ^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.to_string()`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.to_string();`
error: useless use of `format!`
--> $DIR/format.rs:27:5
--> $DIR/format.rs:29:5
|
LL | format!("{:+}", arg); // warn when the format makes no difference
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.to_string()`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.to_string();`
error: useless use of `format!`
--> $DIR/format.rs:28:5
--> $DIR/format.rs:30:5
|
LL | format!("{:<}", arg); // warn when the format makes no difference
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.to_string()`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error: useless use of `format!`
--> $DIR/format.rs:55:5
|
LL | format!("{}", 42.to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: `to_string()` is enough: `42.to_string()`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.to_string();`
error: useless use of `format!`
--> $DIR/format.rs:57:5
|
LL | format!("{}", x.display().to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: `to_string()` is enough: `x.display().to_string()`
LL | format!("{}", 42.to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: `to_string()` is enough: `42.to_string();`
error: useless use of `format!`
--> $DIR/format.rs:59:5
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
LL | format!("{}", x.display().to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: `to_string()` is enough: `x.display().to_string();`
error: aborting due to 9 previous errors