Auto merge of #11750 - Alexendoo:let-chains, r=flip1995

Replace if_chain with let chains

Closes #9353

Let chains are now supported by rustfmt 🎉

The PR is split into two commits
1. The result of running [`if-to-let-chain clippy*/**/*.rs`](https://github.com/Alexendoo/if-to-let-chain)
2. The manual clean up: fixing some errors/formatting, dogfood lints, removing the if_chain internal lint

r? `@flip1995`

changelog: none

Author: bors

Diff for: clippy_lints/Cargo.toml

@@ -14,7 +14,6 @@ cargo_metadata = "0.15.3"
 clippy_config = { path = "../clippy_config" }
 clippy_utils = { path = "../clippy_utils" }
 declare_clippy_lint = { path = "../declare_clippy_lint" }
-if_chain = "1.0"
 itertools = "0.10.1"
 quine-mc_cluskey = "0.2"
 regex-syntax = "0.7"

Diff for: clippy_lints/src/allow_attributes.rs

@@ -52,24 +52,22 @@ declare_lint_pass!(AllowAttribute => [ALLOW_ATTRIBUTES]);
 impl LateLintPass<'_> for AllowAttribute {
     // Separate each crate's features.
     fn check_attribute<'cx>(&mut self, cx: &LateContext<'cx>, attr: &'cx Attribute) {
-        if_chain! {
-            if !in_external_macro(cx.sess(), attr.span);
-            if cx.tcx.features().lint_reasons;
-            if let AttrStyle::Outer = attr.style;
-            if let Some(ident) = attr.ident();
-            if ident.name == rustc_span::symbol::sym::allow;
-            if !is_from_proc_macro(cx, &attr);
-            then {
-                span_lint_and_sugg(
-                    cx,
-                    ALLOW_ATTRIBUTES,
-                    ident.span,
-                    "#[allow] attribute found",
-                    "replace it with",
-                    "expect".into(),
-                    Applicability::MachineApplicable,
-                );
-            }
+        if !in_external_macro(cx.sess(), attr.span)
+            && cx.tcx.features().lint_reasons
+            && let AttrStyle::Outer = attr.style
+            && let Some(ident) = attr.ident()
+            && ident.name == rustc_span::symbol::sym::allow
+            && !is_from_proc_macro(cx, &attr)
+        {
+            span_lint_and_sugg(
+                cx,
+                ALLOW_ATTRIBUTES,
+                ident.span,
+                "#[allow] attribute found",
+                "replace it with",
+                "expect".into(),
+                Applicability::MachineApplicable,
+            );
         }
     }
 }

Diff for: clippy_lints/src/attrs.rs

@@ -5,7 +5,6 @@ use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_sug
 use clippy_utils::is_from_proc_macro;
 use clippy_utils::macros::{is_panic, macro_backtrace};
 use clippy_utils::source::{first_line_of_span, is_present_in_source, snippet_opt, without_block_comments};
-use if_chain::if_chain;
 use rustc_ast::token::{Token, TokenKind};
 use rustc_ast::tokenstream::TokenTree;
 use rustc_ast::{
@@ -471,13 +470,11 @@ impl<'tcx> LateLintPass<'tcx> for Attributes {
                     return;
                 }
                 for item in items {
-                    if_chain! {
-                        if let NestedMetaItem::MetaItem(mi) = &item;
-                        if let MetaItemKind::NameValue(lit) = &mi.kind;
-                        if mi.has_name(sym::since);
-                        then {
-                            check_semver(cx, item.span(), lit);
-                        }
+                    if let NestedMetaItem::MetaItem(mi) = &item
+                        && let MetaItemKind::NameValue(lit) = &mi.kind
+                        && mi.has_name(sym::since)
+                    {
+                        check_semver(cx, item.span(), lit);
                     }
                 }
             }
@@ -580,15 +577,13 @@ impl<'tcx> LateLintPass<'tcx> for Attributes {
 
 /// Returns the lint name if it is clippy lint.
 fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<Symbol> {
-    if_chain! {
-        if let Some(meta_item) = lint.meta_item();
-        if meta_item.path.segments.len() > 1;
-        if let tool_name = meta_item.path.segments[0].ident;
-        if tool_name.name == sym::clippy;
-        then {
-            let lint_name = meta_item.path.segments.last().unwrap().ident.name;
-            return Some(lint_name);
-        }
+    if let Some(meta_item) = lint.meta_item()
+        && meta_item.path.segments.len() > 1
+        && let tool_name = meta_item.path.segments[0].ident
+        && tool_name.name == sym::clippy
+    {
+        let lint_name = meta_item.path.segments.last().unwrap().ident.name;
+        return Some(lint_name);
     }
     None
 }
@@ -857,40 +852,38 @@ fn check_empty_line_after_outer_attr(cx: &EarlyContext<'_>, item: &rustc_ast::It
 }
 
 fn check_deprecated_cfg_attr(cx: &EarlyContext<'_>, attr: &Attribute, msrv: &Msrv) {
-    if_chain! {
-        if msrv.meets(msrvs::TOOL_ATTRIBUTES);
+    if msrv.meets(msrvs::TOOL_ATTRIBUTES)
         // check cfg_attr
-        if attr.has_name(sym::cfg_attr);
-        if let Some(items) = attr.meta_item_list();
-        if items.len() == 2;
+        && attr.has_name(sym::cfg_attr)
+        && let Some(items) = attr.meta_item_list()
+        && items.len() == 2
         // check for `rustfmt`
-        if let Some(feature_item) = items[0].meta_item();
-        if feature_item.has_name(sym::rustfmt);
+        && let Some(feature_item) = items[0].meta_item()
+        && feature_item.has_name(sym::rustfmt)
         // check for `rustfmt_skip` and `rustfmt::skip`
-        if let Some(skip_item) = &items[1].meta_item();
-        if skip_item.has_name(sym!(rustfmt_skip))
+        && let Some(skip_item) = &items[1].meta_item()
+        && (skip_item.has_name(sym!(rustfmt_skip))
             || skip_item
                 .path
                 .segments
                 .last()
                 .expect("empty path in attribute")
                 .ident
                 .name
-                == sym::skip;
+                == sym::skip)
         // Only lint outer attributes, because custom inner attributes are unstable
         // Tracking issue: https://github.com/rust-lang/rust/issues/54726
-        if attr.style == AttrStyle::Outer;
-        then {
-            span_lint_and_sugg(
-                cx,
-                DEPRECATED_CFG_ATTR,
-                attr.span,
-                "`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes",
-                "use",
-                "#[rustfmt::skip]".to_string(),
-                Applicability::MachineApplicable,
-            );
-        }
+        && attr.style == AttrStyle::Outer
+    {
+        span_lint_and_sugg(
+            cx,
+            DEPRECATED_CFG_ATTR,
+            attr.span,
+            "`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes",
+            "use",
+            "#[rustfmt::skip]".to_string(),
+            Applicability::MachineApplicable,
+        );
     }
 }
 
@@ -990,12 +983,10 @@ fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
                         mismatched.extend(find_mismatched_target_os(list));
                     },
                     MetaItemKind::Word => {
-                        if_chain! {
-                            if let Some(ident) = meta.ident();
-                            if let Some(os) = find_os(ident.name.as_str());
-                            then {
-                                mismatched.push((os, ident.span));
-                            }
+                        if let Some(ident) = meta.ident()
+                            && let Some(os) = find_os(ident.name.as_str())
+                        {
+                            mismatched.push((os, ident.span));
                         }
                     },
                     MetaItemKind::NameValue(..) => {},
@@ -1006,30 +997,28 @@ fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
         mismatched
     }
 
-    if_chain! {
-        if attr.has_name(sym::cfg);
-        if let Some(list) = attr.meta_item_list();
-        let mismatched = find_mismatched_target_os(&list);
-        if !mismatched.is_empty();
-        then {
-            let mess = "operating system used in target family position";
-
-            span_lint_and_then(cx, MISMATCHED_TARGET_OS, attr.span, mess, |diag| {
-                // Avoid showing the unix suggestion multiple times in case
-                // we have more than one mismatch for unix-like systems
-                let mut unix_suggested = false;
-
-                for (os, span) in mismatched {
-                    let sugg = format!("target_os = \"{os}\"");
-                    diag.span_suggestion(span, "try", sugg, Applicability::MaybeIncorrect);
-
-                    if !unix_suggested && is_unix(os) {
-                        diag.help("did you mean `unix`?");
-                        unix_suggested = true;
-                    }
+    if attr.has_name(sym::cfg)
+        && let Some(list) = attr.meta_item_list()
+        && let mismatched = find_mismatched_target_os(&list)
+        && !mismatched.is_empty()
+    {
+        let mess = "operating system used in target family position";
+
+        span_lint_and_then(cx, MISMATCHED_TARGET_OS, attr.span, mess, |diag| {
+            // Avoid showing the unix suggestion multiple times in case
+            // we have more than one mismatch for unix-like systems
+            let mut unix_suggested = false;
+
+            for (os, span) in mismatched {
+                let sugg = format!("target_os = \"{os}\"");
+                diag.span_suggestion(span, "try", sugg, Applicability::MaybeIncorrect);
+
+                if !unix_suggested && is_unix(os) {
+                    diag.help("did you mean `unix`?");
+                    unix_suggested = true;
                 }
-            });
-        }
+            }
+        });
     }
 }
 

Diff for: clippy_lints/src/blocks_in_if_conditions.rs

@@ -4,7 +4,6 @@ use clippy_utils::ty::implements_trait;
 use clippy_utils::visitors::{for_each_expr, Descend};
 use clippy_utils::{get_parent_expr, higher};
 use core::ops::ControlFlow;
-use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::{BlockCheckMode, Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
@@ -114,15 +113,13 @@ impl<'tcx> LateLintPass<'tcx> for BlocksInIfConditions {
                 let _: Option<!> = for_each_expr(cond, |e| {
                     if let ExprKind::Closure(closure) = e.kind {
                         // do not lint if the closure is called using an iterator (see #1141)
-                        if_chain! {
-                            if let Some(parent) = get_parent_expr(cx, e);
-                            if let ExprKind::MethodCall(_, self_arg, _, _) = &parent.kind;
-                            let caller = cx.typeck_results().expr_ty(self_arg);
-                            if let Some(iter_id) = cx.tcx.get_diagnostic_item(sym::Iterator);
-                            if implements_trait(cx, caller, iter_id, &[]);
-                            then {
-                                return ControlFlow::Continue(Descend::No);
-                            }
+                        if let Some(parent) = get_parent_expr(cx, e)
+                            && let ExprKind::MethodCall(_, self_arg, _, _) = &parent.kind
+                            && let caller = cx.typeck_results().expr_ty(self_arg)
+                            && let Some(iter_id) = cx.tcx.get_diagnostic_item(sym::Iterator)
+                            && implements_trait(cx, caller, iter_id, &[])
+                        {
+                            return ControlFlow::Continue(Descend::No);
                         }
 
                         let body = cx.tcx.hir().body(closure.body);

Diff for: clippy_lints/src/booleans.rs

@@ -2,7 +2,6 @@ use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then};
 use clippy_utils::eq_expr_value;
 use clippy_utils::source::snippet_opt;
 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
-use if_chain::if_chain;
 use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::{walk_expr, FnKind, Visitor};
@@ -152,17 +151,15 @@ impl<'a, 'tcx, 'v> Hir2Qmm<'a, 'tcx, 'v> {
                 return Ok(Bool::Term(n as u8));
             }
 
-            if_chain! {
-                if let ExprKind::Binary(e_binop, e_lhs, e_rhs) = &e.kind;
-                if implements_ord(self.cx, e_lhs);
-                if let ExprKind::Binary(expr_binop, expr_lhs, expr_rhs) = &expr.kind;
-                if negate(e_binop.node) == Some(expr_binop.node);
-                if eq_expr_value(self.cx, e_lhs, expr_lhs);
-                if eq_expr_value(self.cx, e_rhs, expr_rhs);
-                then {
-                    #[expect(clippy::cast_possible_truncation)]
-                    return Ok(Bool::Not(Box::new(Bool::Term(n as u8))));
-                }
+            if let ExprKind::Binary(e_binop, e_lhs, e_rhs) = &e.kind
+                && implements_ord(self.cx, e_lhs)
+                && let ExprKind::Binary(expr_binop, expr_lhs, expr_rhs) = &expr.kind
+                && negate(e_binop.node) == Some(expr_binop.node)
+                && eq_expr_value(self.cx, e_lhs, expr_lhs)
+                && eq_expr_value(self.cx, e_rhs, expr_rhs)
+            {
+                #[expect(clippy::cast_possible_truncation)]
+                return Ok(Bool::Not(Box::new(Bool::Term(n as u8))));
             }
         }
         let n = self.terminals.len();