Auto merge of #9870 - koka831:unformat-unused-rounding, r=Jarcho

[rust.git] / clippy_lints / src / implicit_saturating_sub.rs

diff --git a/clippy_lints/src/implicit_saturating_sub.rs b/clippy_lints/src/implicit_saturating_sub.rs
index 4088c54623d36a3dc4187589ada0bf02e4345053..29d59c26d92c4a2f697399ff93df5c753bc89152 100644 (file)
--- a/clippy_lints/src/implicit_saturating_sub.rs
+++ b/clippy_lints/src/implicit_saturating_sub.rs
@@ -1,10 +1,9 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::higher;
-use clippy_utils::SpanlessEq;
+use clippy_utils::{higher, is_integer_literal, peel_blocks_with_stmt, SpanlessEq};
 use if_chain::if_chain;
 use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
-use rustc_hir::{lang_items::LangItem, BinOpKind, Expr, ExprKind, QPath, StmtKind};
+use rustc_hir::{BinOpKind, Expr, ExprKind, QPath};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
@@ -17,22 +16,26 @@
     ///
     /// ### Example
     /// ```rust
-    /// let end: u32 = 10;
-    /// let start: u32 = 5;
-    ///
+    /// # let end: u32 = 10;
+    /// # let start: u32 = 5;
     /// let mut i: u32 = end - start;
     ///
-    /// // Bad
     /// if i != 0 {
     ///     i -= 1;
     /// }
+    /// ```
+    ///
+    /// Use instead:
+    /// ```rust
+    /// # let end: u32 = 10;
+    /// # let start: u32 = 5;
+    /// let mut i: u32 = end - start;
     ///
-    /// // Good
     /// i = i.saturating_sub(1);
     /// ```
     #[clippy::version = "1.44.0"]
     pub IMPLICIT_SATURATING_SUB,
-    pedantic,
+    style,
     "Perform saturating subtraction instead of implicitly checking lower bound of data type"
 }
 
@@ -49,16 +52,11 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
             // Check if the conditional expression is a binary operation
             if let ExprKind::Binary(ref cond_op, cond_left, cond_right) = cond.kind;
 
-            // Ensure that the binary operator is >, != and <
+            // Ensure that the binary operator is >, !=, or <
             if BinOpKind::Ne == cond_op.node || BinOpKind::Gt == cond_op.node || BinOpKind::Lt == cond_op.node;
 
-            // Check if the true condition block has only one statement
-            if let ExprKind::Block(block, _) = then.kind;
-            if block.stmts.len() == 1 && block.expr.is_none();
-
             // Check if assign operation is done
-            if let StmtKind::Semi(e) = block.stmts[0].kind;
-            if let Some(target) = subtracts_one(cx, e);
+            if let Some(target) = subtracts_one(cx, then);
 
             // Extracting out the variable name
             if let ExprKind::Path(QPath::Resolved(_, ares_path)) = target.kind;
@@ -88,21 +86,13 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
 
                 // Get the variable name
                 let var_name = ares_path.segments[0].ident.name.as_str();
-                const INT_TYPES: [LangItem; 5] = [
-                    LangItem::I8,
-                    LangItem::I16,
-                    LangItem::I32,
-                    LangItem::I64,
-                    LangItem::Isize
-                ];
-
                 match cond_num_val.kind {
                     ExprKind::Lit(ref cond_lit) => {
                         // Check if the constant is zero
                         if let LitKind::Int(0, _) = cond_lit.node {
                             if cx.typeck_results().expr_ty(cond_left).is_signed() {
                             } else {
-                                print_lint_and_sugg(cx, &var_name, expr);
+                                print_lint_and_sugg(cx, var_name, expr);
                             };
                         }
                     },
@@ -111,10 +101,10 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
                             if name.ident.as_str() == "MIN";
                             if let Some(const_id) = cx.typeck_results().type_dependent_def_id(cond_num_val.hir_id);
                             if let Some(impl_id) = cx.tcx.impl_of_method(const_id);
-                            let mut int_ids = INT_TYPES.iter().filter_map(|&ty| cx.tcx.lang_items().require(ty).ok());
-                            if int_ids.any(|int_id| int_id == impl_id);
+                            if let None = cx.tcx.impl_trait_ref(impl_id); // An inherent impl
+                            if cx.tcx.type_of(impl_id).is_integral();
                             then {
-                                print_lint_and_sugg(cx, &var_name, expr)
+                                print_lint_and_sugg(cx, var_name, expr)
                             }
                         }
                     },
@@ -124,10 +114,10 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
                             if name.ident.as_str() == "min_value";
                             if let Some(func_id) = cx.typeck_results().type_dependent_def_id(func.hir_id);
                             if let Some(impl_id) = cx.tcx.impl_of_method(func_id);
-                            let mut int_ids = INT_TYPES.iter().filter_map(|&ty| cx.tcx.lang_items().require(ty).ok());
-                            if int_ids.any(|int_id| int_id == impl_id);
+                            if let None = cx.tcx.impl_trait_ref(impl_id); // An inherent impl
+                            if cx.tcx.type_of(impl_id).is_integral();
                             then {
-                                print_lint_and_sugg(cx, &var_name, expr)
+                                print_lint_and_sugg(cx, var_name, expr)
                             }
                         }
                     },
@@ -138,20 +128,11 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
     }
 }
 
-fn subtracts_one<'a>(cx: &LateContext<'_>, expr: &Expr<'a>) -> Option<&'a Expr<'a>> {
-    match expr.kind {
+fn subtracts_one<'a>(cx: &LateContext<'_>, expr: &'a Expr<'a>) -> Option<&'a Expr<'a>> {
+    match peel_blocks_with_stmt(expr).kind {
         ExprKind::AssignOp(ref op1, target, value) => {
-            if_chain! {
-                if BinOpKind::Sub == op1.node;
-                // Check if literal being subtracted is one
-                if let ExprKind::Lit(ref lit1) = value.kind;
-                if let LitKind::Int(1, _) = lit1.node;
-                then {
-                    Some(target)
-                } else {
-                    None
-                }
-            }
+            // Check if literal being subtracted is one
+            (BinOpKind::Sub == op1.node && is_integer_literal(value, 1)).then_some(target)
         },
         ExprKind::Assign(target, value, _) => {
             if_chain! {
@@ -160,8 +141,7 @@ fn subtracts_one<'a>(cx: &LateContext<'_>, expr: &Expr<'a>) -> Option<&'a Expr<'
 
                 if SpanlessEq::new(cx).eq_expr(left1, target);
 
-                if let ExprKind::Lit(ref lit1) = right1.kind;
-                if let LitKind::Int(1, _) = lit1.node;
+                if is_integer_literal(right1, 1);
                 then {
                     Some(target)
                 } else {
@@ -180,7 +160,7 @@ fn print_lint_and_sugg(cx: &LateContext<'_>, var_name: &str, expr: &Expr<'_>) {
         expr.span,
         "implicitly performing saturating subtraction",
         "try",
-        format!("{} = {}.saturating_sub({});", var_name, var_name, '1'),
+        format!("{var_name} = {var_name}.saturating_sub({});", '1'),
         Applicability::MachineApplicable,
     );
 }