Merge pull request #2662 from mikerite/issue_2546
Fix useless_format false negative
This commit is contained in:
Oliver Schneider
GitHub
commit
b2e4b88d18
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@ -2,8 +2,9 @@ use rustc::hir::*;
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use rustc::lint::*;
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use rustc::ty;
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use syntax::ast::LitKind;
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use syntax_pos::Span;
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use utils::paths;
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use utils::{in_macro, is_expn_of, match_def_path, match_type, opt_def_id, resolve_node, snippet, span_lint_and_then, walk_ptrs_ty};
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use utils::{in_macro, is_expn_of, last_path_segment, match_def_path, match_type, opt_def_id, resolve_node, snippet, span_lint_and_then, walk_ptrs_ty};
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/// **What it does:** Checks for the use of `format!("string literal with no
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/// argument")` and `format!("{}", foo)` where `foo` is a string.
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@ -43,20 +44,19 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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return;
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}
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match expr.node {
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// `format!("{}", foo)` expansion
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ExprCall(ref fun, ref args) => {
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if_chain! {
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if let ExprPath(ref qpath) = fun.node;
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if args.len() == 2;
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if args.len() == 3;
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if let Some(fun_def_id) = opt_def_id(resolve_node(cx, qpath, fun.hir_id));
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if match_def_path(cx.tcx, fun_def_id, &paths::FMT_ARGUMENTS_NEWV1);
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// ensure the format string is `"{..}"` with only one argument and no text
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if check_static_str(&args[0]);
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// ensure the format argument is `{}` ie. Display with no fancy option
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// and that the argument is a string
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if check_arg_is_display(cx, &args[1]);
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if match_def_path(cx.tcx, fun_def_id, &paths::FMT_ARGUMENTS_NEWV1FORMATTED);
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if check_single_piece(&args[0]);
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if let Some(format_arg) = get_single_string_arg(cx, &args[1]);
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if check_unformatted(&args[2]);
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then {
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let sugg = format!("{}.to_string()", snippet(cx, expr.span, "<expr>").into_owned());
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let sugg = format!("{}.to_string()", snippet(cx, format_arg, "<arg>").into_owned());
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span_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
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db.span_suggestion(expr.span, "consider using .to_string()", sugg);
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});
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@ -79,7 +79,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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}
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/// Checks if the expressions matches `&[""]`
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fn check_static_str(expr: &Expr) -> bool {
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fn check_single_piece(expr: &Expr) -> bool {
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if_chain! {
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if let ExprAddrOf(_, ref expr) = expr.node; // &[""]
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if let ExprArray(ref exprs) = expr.node; // [""]
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@ -96,15 +96,17 @@ fn check_static_str(expr: &Expr) -> bool {
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/// Checks if the expressions matches
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/// ```rust,ignore
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/// &match (&42,) {
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/// &match (&"arg",) {
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/// (__arg0,) => [::std::fmt::ArgumentV1::new(__arg0,
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/// ::std::fmt::Display::fmt)],
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/// }
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/// ```
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fn check_arg_is_display(cx: &LateContext, expr: &Expr) -> bool {
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/// and that type of `__arg0` is `&str` or `String`
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/// then returns the span of first element of the matched tuple
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fn get_single_string_arg(cx: &LateContext, expr: &Expr) -> Option<Span> {
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if_chain! {
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if let ExprAddrOf(_, ref expr) = expr.node;
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if let ExprMatch(_, ref arms, _) = expr.node;
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if let ExprMatch(ref match_expr, ref arms, _) = expr.node;
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if arms.len() == 1;
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if arms[0].pats.len() == 1;
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if let PatKind::Tuple(ref pat, None) = arms[0].pats[0].node;
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@ -118,8 +120,40 @@ fn check_arg_is_display(cx: &LateContext, expr: &Expr) -> bool {
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if match_def_path(cx.tcx, fun_def_id, &paths::DISPLAY_FMT_METHOD);
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then {
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let ty = walk_ptrs_ty(cx.tables.pat_ty(&pat[0]));
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if ty.sty == ty::TyStr || match_type(cx, ty, &paths::STRING) {
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if let ExprTup(ref values) = match_expr.node {
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return Some(values[0].span);
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}
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}
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}
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}
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return ty.sty == ty::TyStr || match_type(cx, ty, &paths::STRING);
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None
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}
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/// Checks if the expression matches
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/// ```rust,ignore
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/// &[_ {
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/// format: _ {
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/// width: _::Implied,
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/// ...
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/// },
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/// ...,
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/// }]
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/// ```
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fn check_unformatted(expr: &Expr) -> bool {
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if_chain! {
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if let ExprAddrOf(_, ref expr) = expr.node;
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if let ExprArray(ref exprs) = expr.node;
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if exprs.len() == 1;
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if let ExprStruct(_, ref fields, _) = exprs[0].node;
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if let Some(format_field) = fields.iter().find(|f| f.name.node == "format");
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if let ExprStruct(_, ref fields, _) = format_field.expr.node;
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if let Some(align_field) = fields.iter().find(|f| f.name.node == "width");
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if let ExprPath(ref qpath) = align_field.expr.node;
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if last_path_segment(qpath).name == "Implied";
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then {
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return true;
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}
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}
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@ -12,15 +12,19 @@ fn main() {
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format!("foo");
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format!("{}", "foo");
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format!("{:?}", "foo"); // we only want to warn about `{}`
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format!("{:+}", "foo"); // we only want to warn about `{}`
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format!("{:?}", "foo"); // don't warn about debug
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format!("{:8}", "foo");
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format!("{:+}", "foo"); // warn when the format makes no difference
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format!("{:<}", "foo"); // warn when the format makes no difference
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format!("foo {}", "bar");
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format!("{} bar", "foo");
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let arg: String = "".to_owned();
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format!("{}", arg);
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format!("{:?}", arg); // we only want to warn about `{}`
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format!("{:+}", arg); // we only want to warn about `{}`
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format!("{:?}", arg); // don't warn about debug
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format!("{:8}", arg);
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format!("{:+}", arg); // warn when the format makes no difference
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format!("{:<}", arg); // warn when the format makes no difference
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format!("foo {}", arg);
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format!("{} bar", arg);
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@ -6,5 +6,53 @@ error: useless use of `format!`
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= note: `-D useless-format` implied by `-D warnings`
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error: aborting due to previous error
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error: useless use of `format!`
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--> $DIR/format.rs:14:5
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14 | format!("{}", "foo");
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| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string()`
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= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
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error: useless use of `format!`
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--> $DIR/format.rs:17:5
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17 | format!("{:+}", "foo"); // warn when the format makes no difference
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| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string()`
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= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
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error: useless use of `format!`
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--> $DIR/format.rs:18:5
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18 | format!("{:<}", "foo"); // warn when the format makes no difference
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| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".to_string()`
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= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
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error: useless use of `format!`
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--> $DIR/format.rs:23:5
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23 | format!("{}", arg);
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| ^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.to_string()`
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= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
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error: useless use of `format!`
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--> $DIR/format.rs:26:5
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26 | format!("{:+}", arg); // warn when the format makes no difference
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| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.to_string()`
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= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
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error: useless use of `format!`
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--> $DIR/format.rs:27:5
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27 | format!("{:<}", arg); // warn when the format makes no difference
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| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.to_string()`
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= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
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error: aborting due to 7 previous errors
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