add lint: could_be_assoc_type_bounds

CHANGELOG.md

@@ -5410,6 +5410,7 @@ Released 2018-09-13
 [`const_is_empty`]: https://rust-lang.github.io/rust-clippy/master/index.html#const_is_empty
 [`const_static_lifetime`]: https://rust-lang.github.io/rust-clippy/master/index.html#const_static_lifetime
 [`copy_iterator`]: https://rust-lang.github.io/rust-clippy/master/index.html#copy_iterator
+[`could_be_assoc_type_bounds`]: https://rust-lang.github.io/rust-clippy/master/index.html#could_be_assoc_type_bounds
 [`crate_in_macro_def`]: https://rust-lang.github.io/rust-clippy/master/index.html#crate_in_macro_def
 [`create_dir`]: https://rust-lang.github.io/rust-clippy/master/index.html#create_dir
 [`crosspointer_transmute`]: https://rust-lang.github.io/rust-clippy/master/index.html#crosspointer_transmute

book/src/lint_configuration.md

@@ -694,6 +694,7 @@ The minimum rust version that the project supports. Defaults to the `rust-versio
 * [`cloned_instead_of_copied`](https://rust-lang.github.io/rust-clippy/master/index.html#cloned_instead_of_copied)
 * [`collapsible_match`](https://rust-lang.github.io/rust-clippy/master/index.html#collapsible_match)
 * [`collapsible_str_replace`](https://rust-lang.github.io/rust-clippy/master/index.html#collapsible_str_replace)
+* [`could_be_assoc_type_bounds`](https://rust-lang.github.io/rust-clippy/master/index.html#could_be_assoc_type_bounds)
 * [`deprecated_cfg_attr`](https://rust-lang.github.io/rust-clippy/master/index.html#deprecated_cfg_attr)
 * [`derivable_impls`](https://rust-lang.github.io/rust-clippy/master/index.html#derivable_impls)
 * [`err_expect`](https://rust-lang.github.io/rust-clippy/master/index.html#err_expect)

clippy_config/src/conf.rs

@@ -577,6 +577,7 @@ define_Conf! {
         cloned_instead_of_copied,
         collapsible_match,
         collapsible_str_replace,
+        could_be_assoc_type_bounds,
         deprecated_cfg_attr,
         derivable_impls,
         err_expect,

clippy_lints/src/declared_lints.rs

@@ -111,6 +111,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::copies::IF_SAME_THEN_ELSE_INFO,
     crate::copies::SAME_FUNCTIONS_IN_IF_CONDITION_INFO,
     crate::copy_iterator::COPY_ITERATOR_INFO,
+    crate::could_be_assoc_type_bounds::COULD_BE_ASSOC_TYPE_BOUNDS_INFO,
     crate::crate_in_macro_def::CRATE_IN_MACRO_DEF_INFO,
     crate::create_dir::CREATE_DIR_INFO,
     crate::dbg_macro::DBG_MACRO_INFO,

clippy_lints/src/lib.rs

@@ -100,6 +100,7 @@ mod collection_is_never_read;
 mod comparison_chain;
 mod copies;
 mod copy_iterator;
+mod could_be_assoc_type_bounds;
 mod crate_in_macro_def;
 mod create_dir;
 mod dbg_macro;
@@ -963,5 +964,6 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     store.register_late_pass(|_| Box::new(manual_ignore_case_cmp::ManualIgnoreCaseCmp));
     store.register_late_pass(|_| Box::new(unnecessary_literal_bound::UnnecessaryLiteralBound));
     store.register_late_pass(move |_| Box::new(arbitrary_source_item_ordering::ArbitrarySourceItemOrdering::new(conf)));
+    store.register_late_pass(move |_| Box::new(could_be_assoc_type_bounds::ManualAssocTypeBounds::new(conf)));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }

clippy_utils/src/hir_utils.rs

@@ -455,7 +455,7 @@ impl HirEqInterExpr<'_, '_, '_> {
         left.ident.name == right.ident.name && self.eq_expr(left.expr, right.expr)
     }
 
-    fn eq_generic_arg(&mut self, left: &GenericArg<'_>, right: &GenericArg<'_>) -> bool {
+    pub fn eq_generic_arg(&mut self, left: &GenericArg<'_>, right: &GenericArg<'_>) -> bool {
         match (left, right) {
             (GenericArg::Const(l), GenericArg::Const(r)) => self.eq_const_arg(l, r),
             (GenericArg::Lifetime(l_lt), GenericArg::Lifetime(r_lt)) => Self::eq_lifetime(l_lt, r_lt),

clippy_utils/src/lib.rs

@@ -79,7 +79,7 @@ pub mod usage;
 pub mod visitors;
 
 pub use self::attrs::*;
-pub use self::check_proc_macro::{is_from_proc_macro, is_span_if, is_span_match};
+pub use self::check_proc_macro::{WithSearchPat, is_from_proc_macro, is_span_if, is_span_match};
 pub use self::hir_utils::{
     HirEqInterExpr, SpanlessEq, SpanlessHash, both, count_eq, eq_expr_value, hash_expr, hash_stmt, is_bool, over,
 };

clippy_utils/src/msrvs.rs

@@ -21,7 +21,8 @@ msrv_aliases! {
     1,83,0 { CONST_EXTERN_FN, CONST_FLOAT_BITS_CONV, CONST_FLOAT_CLASSIFY }
     1,82,0 { IS_NONE_OR, REPEAT_N }
     1,81,0 { LINT_REASONS_STABILIZATION }
-    1,80,0 { BOX_INTO_ITER}
+    1,80,0 { BOX_INTO_ITER }
+    1,79,0 { ASSOCIATED_TYPE_BOUNDS }
     1,77,0 { C_STR_LITERALS }
     1,76,0 { PTR_FROM_REF, OPTION_RESULT_INSPECT }
     1,73,0 { MANUAL_DIV_CEIL }

clippy_utils/src/ty.rs

@@ -251,7 +251,7 @@ pub fn implements_trait_with_env_from_iter<'tcx>(
     ty: Ty<'tcx>,
     trait_id: DefId,
     callee_id: Option<DefId>,
-    args: impl IntoIterator<Item = impl Into<Option<GenericArg<'tcx>>>>,
+    args: impl IntoIterator<Item: Into<Option<GenericArg<'tcx>>>>,
 ) -> bool {
     // Clippy shouldn't have infer types
     assert!(!ty.has_infer());
@@ -1073,7 +1073,7 @@ pub fn make_projection<'tcx>(
     tcx: TyCtxt<'tcx>,
     container_id: DefId,
     assoc_ty: Symbol,
-    args: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+    args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
 ) -> Option<AliasTy<'tcx>> {
     fn helper<'tcx>(
         tcx: TyCtxt<'tcx>,
@@ -1114,7 +1114,7 @@ pub fn make_normalized_projection<'tcx>(
     param_env: ParamEnv<'tcx>,
     container_id: DefId,
     assoc_ty: Symbol,
-    args: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+    args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
 ) -> Option<Ty<'tcx>> {
     fn helper<'tcx>(tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: AliasTy<'tcx>) -> Option<Ty<'tcx>> {
         #[cfg(debug_assertions)]
@@ -1241,7 +1241,7 @@ pub fn make_normalized_projection_with_regions<'tcx>(
     param_env: ParamEnv<'tcx>,
     container_id: DefId,
     assoc_ty: Symbol,
-    args: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+    args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
 ) -> Option<Ty<'tcx>> {
     fn helper<'tcx>(tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: AliasTy<'tcx>) -> Option<Ty<'tcx>> {
         #[cfg(debug_assertions)]

tests/ui/could_be_assoc_type_bounds.fixed

@@ -0,0 +1,95 @@
+//@aux-build:proc_macros.rs
+#![allow(clippy::extra_unused_type_parameters)]
+
+extern crate proc_macros;
+
+fn projection_with_existing_assoc_bounds<T>()
+where
+    T: Iterator<Item: Clone + Copy + Sized>,
+
+    //~^ could_be_assoc_type_bounds
+{
+}
+
+fn projection_with_existing_bounds<T: Iterator<Item: Clone + Copy + Sized>>()
+    //~^ could_be_assoc_type_bounds
+{
+}
+
+fn no_fully_qualified_path<T: Iterator<Item: Clone>>()
+where
+    // False negative for now: `T::Item` has a `Res::Err` resolution
+    T::Item: Copy + Sized,
+{
+}
+
+fn ty_param<T: Iterator<Item: Clone>, >() {}
+
+fn multiple_projections<T>()
+where
+    T: Iterator<Item: Sized + Clone>,
+
+{
+}
+
+fn ty_param_used_in_body<T: Iterator<Item = P>, P: Clone + Default>() {
+    P::default();
+}
+
+fn nested_impl_trait(_: impl Iterator<Item = impl Sized>) {}
+
+fn impl_trait_generic(_: impl Iterator<Item: Copy>) {}
+
+fn single_impl_trait(_: impl Iterator<Item = ()>) {}
+
+fn parenthesized<T: Iterator<Item: Fn()>, >() {} //~ could_be_assoc_type_bounds
+
+// Make sure implicit generic lifetime parameters for delim doesn't mess up spans
+pub fn elided_lifetime<I, >(iter: I, delim: &str)
+where
+    I: IntoIterator<Item: std::fmt::Display>,
+     //~ could_be_assoc_type_bounds
+{
+}
+
+fn parenthesized2<F: Fn()>()
+where
+    F::Output: Copy,
+{
+}
+fn many_ty_params<T, X>()
+//~^ could_be_assoc_type_bounds
+where
+    T: Iterator<Item: Copy>,
+{
+}
+
+#[clippy::msrv = "1.78.0"]
+fn low_msrv<T: Iterator<Item = P>, P: Copy + Default>() {
+    #[clippy::msrv = "1.79.0"]
+    P::default();
+}
+
+// More involved test case with multiple associated types and generic parameters
+trait Trait1<G1, G2>: Default {
+    type A2;
+    type A3;
+    type A4;
+}
+
+fn complex<T, G1, G2>()
+where
+    (T, T): Trait1<G1, G2, A2 = u32, A3: Clone, A4: Clone>,
+
+{
+}
+
+proc_macros::external! {
+    fn external<T: Iterator<Item = I>, I: Copy>() {}
+}
+proc_macros::with_span! {
+    span
+    fn external2<T: Iterator<Item = I>, I: Copy>() {}
+}
+
+fn main() {}

tests/ui/could_be_assoc_type_bounds.rs

@@ -0,0 +1,101 @@
+//@aux-build:proc_macros.rs
+#![allow(clippy::extra_unused_type_parameters)]
+
+extern crate proc_macros;
+
+fn projection_with_existing_assoc_bounds<T>()
+where
+    T: Iterator<Item: Clone>,
+    <T as Iterator>::Item: Copy + Sized,
+    //~^ could_be_assoc_type_bounds
+{
+}
+
+fn projection_with_existing_bounds<T: Iterator<Item: Clone>>()
+where
+    <T as Iterator>::Item: Copy + Sized,
+    //~^ could_be_assoc_type_bounds
+{
+}
+
+fn no_fully_qualified_path<T: Iterator<Item: Clone>>()
+where
+    // False negative for now: `T::Item` has a `Res::Err` resolution
+    T::Item: Copy + Sized,
+{
+}
+
+fn ty_param<T: Iterator<Item = P>, P: Clone>() {}
+
+fn multiple_projections<T>()
+where
+    T: Iterator,
+    <T as Iterator>::Item: Sized,
+    //~^ could_be_assoc_type_bounds
+    <T as Iterator>::Item: Clone,
+{
+}
+
+fn ty_param_used_in_body<T: Iterator<Item = P>, P: Clone + Default>() {
+    P::default();
+}
+
+fn nested_impl_trait(_: impl Iterator<Item = impl Sized>) {}
+
+fn impl_trait_generic<T: Copy>(_: impl Iterator<Item = T>) {}
+
+fn single_impl_trait(_: impl Iterator<Item = ()>) {}
+
+fn parenthesized<T: Iterator<Item = F>, F: Fn()>() {} //~ could_be_assoc_type_bounds
+
+// Make sure implicit generic lifetime parameters for delim doesn't mess up spans
+pub fn elided_lifetime<I, T>(iter: I, delim: &str)
+where
+    I: IntoIterator<Item = T>,
+    T: std::fmt::Display, //~ could_be_assoc_type_bounds
+{
+}
+
+fn parenthesized2<F: Fn()>()
+where
+    F::Output: Copy,
+{
+}
+fn many_ty_params<T, U: Copy, X>()
+//~^ could_be_assoc_type_bounds
+where
+    T: Iterator<Item = U>,
+{
+}
+
+#[clippy::msrv = "1.78.0"]
+fn low_msrv<T: Iterator<Item = P>, P: Copy + Default>() {
+    #[clippy::msrv = "1.79.0"]
+    P::default();
+}
+
+// More involved test case with multiple associated types and generic parameters
+trait Trait1<G1, G2>: Default {
+    type A2;
+    type A3;
+    type A4;
+}
+
+fn complex<T, U, G1, G2>()
+where
+    (T, T): Trait1<G1, G2, A2 = u32, A3 = U>,
+    <(T, T) as Trait1<G1, G2>>::A4: Clone,
+    //~^ could_be_assoc_type_bounds
+    U: Clone,
+{
+}
+
+proc_macros::external! {
+    fn external<T: Iterator<Item = I>, I: Copy>() {}
+}
+proc_macros::with_span! {
+    span
+    fn external2<T: Iterator<Item = I>, I: Copy>() {}
+}
+
+fn main() {}