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Extend useless_conversion
lint with TryFrom
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@ -1,13 +1,16 @@
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use crate::utils::{
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match_def_path, match_trait_method, paths, same_tys, snippet, snippet_with_macro_callsite, span_lint_and_sugg,
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is_type_diagnostic_item, match_def_path, match_trait_method, paths, same_tys, snippet, snippet_with_macro_callsite,
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span_lint_and_help, span_lint_and_sugg,
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};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, HirId, MatchSource};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty;
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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declare_clippy_lint! {
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/// **What it does:** Checks for `Into`/`From`/`IntoIter` calls that useless converts
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/// **What it does:** Checks for `Into`, `From`, `TryFrom`,`IntoIter` calls that useless converts
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/// to the same type as caller.
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///
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/// **Why is this bad?** Redundant code.
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@ -26,7 +29,7 @@ declare_clippy_lint! {
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/// ```
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pub USELESS_CONVERSION,
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complexity,
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"calls to `Into`/`From`/`IntoIter` that performs useless conversions to the same type"
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"calls to `Into`, `From`, `TryFrom`, `IntoIter` that performs useless conversions to the same type"
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}
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#[derive(Default)]
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@ -68,7 +71,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessConversion {
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cx,
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USELESS_CONVERSION,
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e.span,
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"useless conversion",
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"Useless conversion to the same type",
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"consider removing `.into()`",
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sugg,
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Applicability::MachineApplicable, // snippet
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@ -84,7 +87,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessConversion {
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cx,
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USELESS_CONVERSION,
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e.span,
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"useless conversion",
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"Useless conversion to the same type",
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"consider removing `.into_iter()`",
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sugg,
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Applicability::MachineApplicable, // snippet
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@ -94,11 +97,35 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessConversion {
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},
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ExprKind::Call(ref path, ref args) => {
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if let ExprKind::Path(ref qpath) = path.kind {
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if let Some(def_id) = cx.tables.qpath_res(qpath, path.hir_id).opt_def_id() {
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if_chain! {
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if args.len() == 1;
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if let ExprKind::Path(ref qpath) = path.kind;
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if let Some(def_id) = cx.tables.qpath_res(qpath, path.hir_id).opt_def_id();
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let a = cx.tables.expr_ty(e);
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let b = cx.tables.expr_ty(&args[0]);
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then {
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if_chain! {
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if match_def_path(cx, def_id, &paths::TRY_FROM);
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if is_type_diagnostic_item(cx, a, sym!(result_type));
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if let ty::Adt(_, substs) = a.kind;
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if let Some(a_type) = substs.types().nth(0);
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if same_tys(cx, a_type, b);
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then {
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let hint = format!("consider removing `{}()`", snippet(cx, path.span, "TryFrom::try_from"));
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span_lint_and_help(
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cx,
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USELESS_CONVERSION,
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e.span,
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"Useless conversion to the same type",
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None,
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&hint,
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);
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}
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}
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if match_def_path(cx, def_id, &paths::FROM_FROM) {
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let a = cx.tables.expr_ty(e);
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let b = cx.tables.expr_ty(&args[0]);
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if same_tys(cx, a, b) {
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let sugg = snippet(cx, args[0].span.source_callsite(), "<expr>").into_owned();
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let sugg_msg =
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@ -107,7 +134,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessConversion {
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cx,
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USELESS_CONVERSION,
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e.span,
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"useless conversion",
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"Useless conversion to the same type",
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&sugg_msg,
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sugg,
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Applicability::MachineApplicable, // snippet
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@ -128,6 +128,7 @@ pub const TO_OWNED_METHOD: [&str; 4] = ["alloc", "borrow", "ToOwned", "to_owned"
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pub const TO_STRING: [&str; 3] = ["alloc", "string", "ToString"];
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pub const TO_STRING_METHOD: [&str; 4] = ["alloc", "string", "ToString", "to_string"];
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pub const TRANSMUTE: [&str; 4] = ["core", "intrinsics", "", "transmute"];
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pub const TRY_FROM: [&str; 4] = ["core", "convert", "TryFrom", "try_from"];
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pub const TRY_FROM_ERROR: [&str; 4] = ["std", "ops", "Try", "from_error"];
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pub const TRY_INTO_RESULT: [&str; 4] = ["std", "ops", "Try", "into_result"];
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pub const VEC: [&str; 3] = ["alloc", "vec", "Vec"];
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@ -1,4 +1,4 @@
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:6:13
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LL | let _ = T::from(val);
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@ -10,55 +10,55 @@ note: the lint level is defined here
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LL | #![deny(clippy::useless_conversion)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:7:5
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LL | val.into()
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| ^^^^^^^^^^ help: consider removing `.into()`: `val`
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:19:22
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LL | let _: i32 = 0i32.into();
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| ^^^^^^^^^^^ help: consider removing `.into()`: `0i32`
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:51:21
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LL | let _: String = "foo".to_string().into();
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| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into()`: `"foo".to_string()`
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:52:21
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LL | let _: String = From::from("foo".to_string());
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `From::from()`: `"foo".to_string()`
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:53:13
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LL | let _ = String::from("foo".to_string());
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `String::from()`: `"foo".to_string()`
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:54:13
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LL | let _ = String::from(format!("A: {:04}", 123));
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `String::from()`: `format!("A: {:04}", 123)`
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:55:13
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LL | let _ = "".lines().into_iter();
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| ^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `"".lines()`
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:56:13
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LL | let _ = vec![1, 2, 3].into_iter().into_iter();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `vec![1, 2, 3].into_iter()`
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error: useless conversion
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error: Useless conversion to the same type
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--> $DIR/useless_conversion.rs:57:21
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LL | let _: String = format!("Hello {}", "world").into();
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25
tests/ui/useless_conversion_try.rs
Normal file
25
tests/ui/useless_conversion_try.rs
Normal file
@ -0,0 +1,25 @@
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#![deny(clippy::useless_conversion)]
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use std::convert::TryFrom;
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fn test_generic<T: Copy>(val: T) -> T {
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T::try_from(val).unwrap()
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}
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fn test_generic2<T: Copy + Into<i32> + Into<U>, U: From<T>>(val: T) {
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let _ = U::try_from(val).unwrap();
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}
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fn main() {
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test_generic(10i32);
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test_generic2::<i32, i32>(10i32);
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let _: String = TryFrom::try_from("foo").unwrap();
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let _ = String::try_from("foo").unwrap();
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#[allow(clippy::useless_conversion)]
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let _ = String::try_from("foo").unwrap();
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let _: String = TryFrom::try_from("foo".to_string()).unwrap();
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let _ = String::try_from("foo".to_string()).unwrap();
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let _ = String::try_from(format!("A: {:04}", 123)).unwrap();
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}
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39
tests/ui/useless_conversion_try.stderr
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39
tests/ui/useless_conversion_try.stderr
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@ -0,0 +1,39 @@
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error: Useless conversion to the same type
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--> $DIR/useless_conversion_try.rs:6:5
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LL | T::try_from(val).unwrap()
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| ^^^^^^^^^^^^^^^^
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note: the lint level is defined here
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--> $DIR/useless_conversion_try.rs:1:9
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LL | #![deny(clippy::useless_conversion)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: consider removing `T::try_from()`
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error: Useless conversion to the same type
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--> $DIR/useless_conversion_try.rs:22:21
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LL | let _: String = TryFrom::try_from("foo".to_string()).unwrap();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: consider removing `TryFrom::try_from()`
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error: Useless conversion to the same type
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--> $DIR/useless_conversion_try.rs:23:13
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LL | let _ = String::try_from("foo".to_string()).unwrap();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: consider removing `String::try_from()`
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error: Useless conversion to the same type
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--> $DIR/useless_conversion_try.rs:24:13
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LL | let _ = String::try_from(format!("A: {:04}", 123)).unwrap();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: consider removing `String::try_from()`
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error: aborting due to 4 previous errors
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