Auto merge of #6896 - TaKO8Ki:refactor-lints-in-methods-module, r=phansch

Refactor lints in methods module

This PR refactors methods lints other than the lints I refactored in #6826 and moves some functions to methods/utils.rs.
Basically, I follow the instruction described in #6680.

**For ease of review, I refactored step by step, keeping each commit small.**

closes #6886
cc: `@phansch,` `@flip1995,` `@Y-Nak`

changelog: Move lints in methods module to their own modules and some function to methods/utils.rs.

Author: bors

clippy_lints/src/methods/chars_cmp.rs

@@ -0,0 +1,54 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet_with_applicability;
+use clippy_utils::{method_chain_args, single_segment_path};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_lint::Lint;
+use rustc_middle::ty;
+use rustc_span::sym;
+
+/// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
+pub(super) fn check(
+    cx: &LateContext<'_>,
+    info: &crate::methods::BinaryExprInfo<'_>,
+    chain_methods: &[&str],
+    lint: &'static Lint,
+    suggest: &str,
+) -> bool {
+    if_chain! {
+        if let Some(args) = method_chain_args(info.chain, chain_methods);
+        if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.kind;
+        if arg_char.len() == 1;
+        if let hir::ExprKind::Path(ref qpath) = fun.kind;
+        if let Some(segment) = single_segment_path(qpath);
+        if segment.ident.name == sym::Some;
+        then {
+            let mut applicability = Applicability::MachineApplicable;
+            let self_ty = cx.typeck_results().expr_ty_adjusted(&args[0][0]).peel_refs();
+
+            if *self_ty.kind() != ty::Str {
+                return false;
+            }
+
+            span_lint_and_sugg(
+                cx,
+                lint,
+                info.expr.span,
+                &format!("you should use the `{}` method", suggest),
+                "like this",
+                format!("{}{}.{}({})",
+                        if info.eq { "" } else { "!" },
+                        snippet_with_applicability(cx, args[0][0].span, "..", &mut applicability),
+                        suggest,
+                        snippet_with_applicability(cx, arg_char[0].span, "..", &mut applicability)),
+                applicability,
+            );
+
+            return true;
+        }
+    }
+
+    false
+}

clippy_lints/src/methods/chars_cmp_with_unwrap.rs

@@ -0,0 +1,44 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::method_chain_args;
+use clippy_utils::source::snippet_with_applicability;
+use if_chain::if_chain;
+use rustc_ast::ast;
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_lint::Lint;
+
+/// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    info: &crate::methods::BinaryExprInfo<'_>,
+    chain_methods: &[&str],
+    lint: &'static Lint,
+    suggest: &str,
+) -> bool {
+    if_chain! {
+        if let Some(args) = method_chain_args(info.chain, chain_methods);
+        if let hir::ExprKind::Lit(ref lit) = info.other.kind;
+        if let ast::LitKind::Char(c) = lit.node;
+        then {
+            let mut applicability = Applicability::MachineApplicable;
+            span_lint_and_sugg(
+                cx,
+                lint,
+                info.expr.span,
+                &format!("you should use the `{}` method", suggest),
+                "like this",
+                format!("{}{}.{}('{}')",
+                        if info.eq { "" } else { "!" },
+                        snippet_with_applicability(cx, args[0][0].span, "..", &mut applicability),
+                        suggest,
+                        c),
+                applicability,
+            );
+
+            true
+        } else {
+            false
+        }
+    }
+}

clippy_lints/src/methods/chars_last_cmp.rs

@@ -0,0 +1,13 @@
+use crate::methods::chars_cmp;
+use rustc_lint::LateContext;
+
+use super::CHARS_LAST_CMP;
+
+/// Checks for the `CHARS_LAST_CMP` lint.
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, info: &crate::methods::BinaryExprInfo<'_>) -> bool {
+    if chars_cmp::check(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
+        true
+    } else {
+        chars_cmp::check(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
+    }
+}

clippy_lints/src/methods/chars_last_cmp_with_unwrap.rs

@@ -0,0 +1,13 @@
+use crate::methods::chars_cmp_with_unwrap;
+use rustc_lint::LateContext;
+
+use super::CHARS_LAST_CMP;
+
+/// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, info: &crate::methods::BinaryExprInfo<'_>) -> bool {
+    if chars_cmp_with_unwrap::check(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
+        true
+    } else {
+        chars_cmp_with_unwrap::check(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
+    }
+}

clippy_lints/src/methods/chars_next_cmp.rs

@@ -0,0 +1,8 @@
+use rustc_lint::LateContext;
+
+use super::CHARS_NEXT_CMP;
+
+/// Checks for the `CHARS_NEXT_CMP` lint.
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, info: &crate::methods::BinaryExprInfo<'_>) -> bool {
+    crate::methods::chars_cmp::check(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
+}

clippy_lints/src/methods/chars_next_cmp_with_unwrap.rs

@@ -0,0 +1,8 @@
+use rustc_lint::LateContext;
+
+use super::CHARS_NEXT_CMP;
+
+/// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, info: &crate::methods::BinaryExprInfo<'_>) -> bool {
+    crate::methods::chars_cmp_with_unwrap::check(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
+}

clippy_lints/src/methods/clone_on_copy.rs

@@ -4,14 +4,20 @@ use clippy_utils::ty::is_copy;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
-use rustc_middle::ty::{self, Ty};
+use rustc_middle::ty;
+use rustc_span::symbol::{sym, Symbol};
 use std::iter;
 
 use super::CLONE_DOUBLE_REF;
 use super::CLONE_ON_COPY;
 
 /// Checks for the `CLONE_ON_COPY` lint.
-pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>, arg_ty: Ty<'_>) {
+pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, method_name: Symbol, args: &[hir::Expr<'_>]) {
+    if !(args.len() == 1 && method_name == sym::clone) {
+        return;
+    }
+    let arg = &args[0];
+    let arg_ty = cx.typeck_results().expr_ty_adjusted(&args[0]);
     let ty = cx.typeck_results().expr_ty(expr);
     if let ty::Ref(_, inner, _) = arg_ty.kind() {
         if let ty::Ref(_, innermost, _) = inner.kind() {

clippy_lints/src/methods/clone_on_ref_ptr.rs

@@ -6,11 +6,15 @@ use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
 use rustc_middle::ty;
-use rustc_span::symbol::sym;
+use rustc_span::symbol::{sym, Symbol};
 
 use super::CLONE_ON_REF_PTR;
 
-pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
+pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, method_name: Symbol, args: &[hir::Expr<'_>]) {
+    if !(args.len() == 1 && method_name == sym::clone) {
+        return;
+    }
+    let arg = &args[0];
     let obj_ty = cx.typeck_results().expr_ty(arg).peel_refs();
 
     if let ty::Adt(_, subst) = obj_ty.kind() {

clippy_lints/src/methods/filter_flat_map.rs

@@ -7,12 +7,7 @@ use rustc_span::sym;
 use super::FILTER_MAP;
 
 /// lint use of `filter().flat_map()` for `Iterators`
-pub(super) fn check<'tcx>(
-    cx: &LateContext<'tcx>,
-    expr: &'tcx hir::Expr<'_>,
-    _filter_args: &'tcx [hir::Expr<'_>],
-    _map_args: &'tcx [hir::Expr<'_>],
-) {
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
     // lint if caller of `.filter().flat_map()` is an Iterator
     if is_trait_method(cx, expr, sym::Iterator) {
         let msg = "called `filter(..).flat_map(..)` on an `Iterator`";

clippy_lints/src/methods/filter_map_flat_map.rs

@@ -7,12 +7,7 @@ use rustc_span::sym;
 use super::FILTER_MAP;
 
 /// lint use of `filter_map().flat_map()` for `Iterators`
-pub(super) fn check<'tcx>(
-    cx: &LateContext<'tcx>,
-    expr: &'tcx hir::Expr<'_>,
-    _filter_args: &'tcx [hir::Expr<'_>],
-    _map_args: &'tcx [hir::Expr<'_>],
-) {
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
     // lint if caller of `.filter_map().flat_map()` is an Iterator
     if is_trait_method(cx, expr, sym::Iterator) {
         let msg = "called `filter_map(..).flat_map(..)` on an `Iterator`";