-use crate::utils::{higher, in_macro, span_lint_and_sugg};
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::{in_macro, match_qpath, SpanlessEq};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
declare_clippy_lint! {
/// **What it does:** Checks for implicit saturating subtraction.
///
- /// **Why is this bad?** Simplicity and readability. Instead we can easily use an inbuilt function.
+ /// **Why is this bad?** Simplicity and readability. Instead we can easily use an builtin function.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
- /// let end = 10;
- /// let start = 5;
+ /// let end: u32 = 10;
+ /// let start: u32 = 5;
///
- /// let mut i = end - start;
+ /// let mut i: u32 = end - start;
///
/// // Bad
/// if i != 0 {
/// i -= 1;
/// }
- /// ```
- /// Use instead:
- /// ```rust
- /// let end = 10;
- /// let start = 5;
- ///
- /// let mut i = end - start;
///
/// // Good
- /// i.saturating_sub(1);
+ /// i = i.saturating_sub(1);
/// ```
pub IMPLICIT_SATURATING_SUB,
pedantic,
declare_lint_pass!(ImplicitSaturatingSub => [IMPLICIT_SATURATING_SUB]);
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitSaturatingSub {
- fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) {
+impl<'tcx> LateLintPass<'tcx> for ImplicitSaturatingSub {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
if in_macro(expr.span) {
return;
}
if_chain! {
- if let Some((ref cond, ref then, None)) = higher::if_block(&expr);
+ if let ExprKind::If(cond, then, None) = &expr.kind;
+
// Check if the conditional expression is a binary operation
- if let ExprKind::Binary(ref op, ref left, ref right) = cond.kind;
- // Ensure that the binary operator is > or !=
- if BinOpKind::Ne == op.node || BinOpKind::Gt == op.node;
- if let ExprKind::Path(ref cond_path) = left.kind;
- // Get the literal on the right hand side
- if let ExprKind::Lit(ref lit) = right.kind;
- if let LitKind::Int(0, _) = lit.node;
+ if let ExprKind::Binary(ref cond_op, ref cond_left, ref cond_right) = cond.kind;
+
+ // Ensure that the binary operator is >, != and <
+ 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(ref block, _) = then.kind;
- if block.stmts.len() == 1;
+ if block.stmts.len() == 1 && block.expr.is_none();
+
// Check if assign operation is done
if let StmtKind::Semi(ref e) = block.stmts[0].kind;
- if let ExprKind::AssignOp(ref op1, ref target, ref value) = e.kind;
- if BinOpKind::Sub == op1.node;
- if let ExprKind::Path(ref assign_path) = target.kind;
- // Check if the variable in the condition and assignment statement are the same
- if let (QPath::Resolved(_, ref cres_path), QPath::Resolved(_, ref ares_path)) = (cond_path, assign_path);
- if cres_path.res == ares_path.res;
- if let ExprKind::Lit(ref lit1) = value.kind;
- if let LitKind::Int(assign_lit, _) = lit1.node;
+ if let Some(target) = subtracts_one(cx, e);
+
+ // Extracting out the variable name
+ if let ExprKind::Path(QPath::Resolved(_, ref ares_path)) = target.kind;
+
then {
+ // Handle symmetric conditions in the if statement
+ let (cond_var, cond_num_val) = if SpanlessEq::new(cx).eq_expr(cond_left, target) {
+ if BinOpKind::Gt == cond_op.node || BinOpKind::Ne == cond_op.node {
+ (cond_left, cond_right)
+ } else {
+ return;
+ }
+ } else if SpanlessEq::new(cx).eq_expr(cond_right, target) {
+ if BinOpKind::Lt == cond_op.node || BinOpKind::Ne == cond_op.node {
+ (cond_right, cond_left)
+ } else {
+ return;
+ }
+ } else {
+ return;
+ };
+
+ // Check if the variable in the condition statement is an integer
+ if !cx.typeck_results().expr_ty(cond_var).is_integral() {
+ return;
+ }
+
// Get the variable name
let var_name = ares_path.segments[0].ident.name.as_str();
- let applicability = Applicability::MaybeIncorrect;
- span_lint_and_sugg(
- cx,
- IMPLICIT_SATURATING_SUB,
- expr.span,
- "Implicitly performing saturating subtraction",
- "try",
- format!("{}.saturating_sub({});", var_name, assign_lit.to_string()),
- applicability
- );
+ const INT_TYPES: [&str; 5] = ["i8", "i16", "i32", "i64", "i128"];
+
+ 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);
+ };
+ }
+ },
+ ExprKind::Path(ref cond_num_path) => {
+ if INT_TYPES.iter().any(|int_type| match_qpath(cond_num_path, &[int_type, "MIN"])) {
+ print_lint_and_sugg(cx, &var_name, expr);
+ };
+ },
+ ExprKind::Call(ref func, _) => {
+ if let ExprKind::Path(ref cond_num_path) = func.kind {
+ if INT_TYPES.iter().any(|int_type| match_qpath(cond_num_path, &[int_type, "min_value"])) {
+ print_lint_and_sugg(cx, &var_name, expr);
+ }
+ };
+ },
+ _ => (),
+ }
}
}
}
}
+
+fn subtracts_one<'a>(cx: &LateContext<'_>, expr: &Expr<'a>) -> Option<&'a Expr<'a>> {
+ match expr.kind {
+ ExprKind::AssignOp(ref op1, ref target, ref 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
+ }
+ }
+ },
+ ExprKind::Assign(ref target, ref value, _) => {
+ if_chain! {
+ if let ExprKind::Binary(ref op1, ref left1, ref right1) = value.kind;
+ if BinOpKind::Sub == op1.node;
+
+ if SpanlessEq::new(cx).eq_expr(left1, target);
+
+ if let ExprKind::Lit(ref lit1) = right1.kind;
+ if let LitKind::Int(1, _) = lit1.node;
+ then {
+ Some(target)
+ } else {
+ None
+ }
+ }
+ },
+ _ => None,
+ }
+}
+
+fn print_lint_and_sugg(cx: &LateContext<'_>, var_name: &str, expr: &Expr<'_>) {
+ span_lint_and_sugg(
+ cx,
+ IMPLICIT_SATURATING_SUB,
+ expr.span,
+ "implicitly performing saturating subtraction",
+ "try",
+ format!("{} = {}.saturating_sub({});", var_name, var_name, '1'),
+ Applicability::MachineApplicable,
+ );
+}
projects / rust.git / blobdiff