Rollup merge of #91562 - dtolnay:asyncspace, r=Mark-Simulacrum

[rust.git] / src / tools / clippy / clippy_lints / src / strings.rs

diff --git a/src/tools/clippy/clippy_lints/src/strings.rs b/src/tools/clippy/clippy_lints/src/strings.rs
index 35b6bde56964c17f64c1f711dae4ed77fe9839d0..368274440d5dcb23551ed30be7d4a8ba5f808ece 100644 (file)
--- a/src/tools/clippy/clippy_lints/src/strings.rs
+++ b/src/tools/clippy/clippy_lints/src/strings.rs
@@ -31,6 +31,7 @@
     /// x += ", World";
     /// x.push_str(", World");
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub STRING_ADD_ASSIGN,
     pedantic,
     "using `x = x + ..` where x is a `String` instead of `push_str()`"
@@ -58,6 +59,7 @@
     /// let x = "Hello".to_owned();
     /// x + ", World";
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub STRING_ADD,
     restriction,
     "using `x + ..` where x is a `String` instead of `push_str()`"
@@ -102,56 +104,94 @@
     /// // Good
     /// let bs = b"a byte string";
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub STRING_LIT_AS_BYTES,
     nursery,
     "calling `as_bytes` on a string literal instead of using a byte string literal"
 }
 
-declare_lint_pass!(StringAdd => [STRING_ADD, STRING_ADD_ASSIGN]);
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for slice operations on strings
+    ///
+    /// ### Why is this bad?
+    /// UTF-8 characters span multiple bytes, and it is easy to inadvertently confuse character
+    /// counts and string indices. This may lead to panics, and should warrant some test cases
+    /// containing wide UTF-8 characters. This lint is most useful in code that should avoid
+    /// panics at all costs.
+    ///
+    /// ### Known problems
+    /// Probably lots of false positives. If an index comes from a known valid position (e.g.
+    /// obtained via `char_indices` over the same string), it is totally OK.
+    ///
+    /// # Example
+    /// ```rust,should_panic
+    /// &"Ölkanne"[1..];
+    /// ```
+    #[clippy::version = "1.58.0"]
+    pub STRING_SLICE,
+    restriction,
+    "slicing a string"
+}
+
+declare_lint_pass!(StringAdd => [STRING_ADD, STRING_ADD_ASSIGN, STRING_SLICE]);
 
 impl<'tcx> LateLintPass<'tcx> for StringAdd {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
         if in_external_macro(cx.sess(), e.span) {
             return;
         }
-
-        if let ExprKind::Binary(
-            Spanned {
-                node: BinOpKind::Add, ..
-            },
-            left,
-            _,
-        ) = e.kind
-        {
-            if is_string(cx, left) {
-                if !is_lint_allowed(cx, STRING_ADD_ASSIGN, e.hir_id) {
-                    let parent = get_parent_expr(cx, e);
-                    if let Some(p) = parent {
-                        if let ExprKind::Assign(target, _, _) = p.kind {
-                            // avoid duplicate matches
-                            if SpanlessEq::new(cx).eq_expr(target, left) {
-                                return;
+        match e.kind {
+            ExprKind::Binary(
+                Spanned {
+                    node: BinOpKind::Add, ..
+                },
+                left,
+                _,
+            ) => {
+                if is_string(cx, left) {
+                    if !is_lint_allowed(cx, STRING_ADD_ASSIGN, e.hir_id) {
+                        let parent = get_parent_expr(cx, e);
+                        if let Some(p) = parent {
+                            if let ExprKind::Assign(target, _, _) = p.kind {
+                                // avoid duplicate matches
+                                if SpanlessEq::new(cx).eq_expr(target, left) {
+                                    return;
+                                }
                             }
                         }
                     }
+                    span_lint(
+                        cx,
+                        STRING_ADD,
+                        e.span,
+                        "you added something to a string. Consider using `String::push_str()` instead",
+                    );
                 }
-                span_lint(
-                    cx,
-                    STRING_ADD,
-                    e.span,
-                    "you added something to a string. Consider using `String::push_str()` instead",
-                );
-            }
-        } else if let ExprKind::Assign(target, src, _) = e.kind {
-            if is_string(cx, target) && is_add(cx, src, target) {
-                span_lint(
-                    cx,
-                    STRING_ADD_ASSIGN,
-                    e.span,
-                    "you assigned the result of adding something to this string. Consider using \
-                     `String::push_str()` instead",
-                );
-            }
+            },
+            ExprKind::Assign(target, src, _) => {
+                if is_string(cx, target) && is_add(cx, src, target) {
+                    span_lint(
+                        cx,
+                        STRING_ADD_ASSIGN,
+                        e.span,
+                        "you assigned the result of adding something to this string. Consider using \
+                         `String::push_str()` instead",
+                    );
+                }
+            },
+            ExprKind::Index(target, _idx) => {
+                let e_ty = cx.typeck_results().expr_ty(target).peel_refs();
+                if matches!(e_ty.kind(), ty::Str) || is_type_diagnostic_item(cx, e_ty, sym::String) {
+                    span_lint(
+                        cx,
+                        STRING_SLICE,
+                        e.span,
+                        "indexing into a string may panic if the index is within a UTF-8 character",
+                    );
+                }
+            },
+            _ => {},
         }
     }
 }
@@ -191,6 +231,7 @@ fn is_add(cx: &LateContext<'_>, src: &Expr<'_>, target: &Expr<'_>) -> bool {
     /// ```rust
     /// let _ = &"Hello World!"[6..11];
     /// ```
+    #[clippy::version = "1.50.0"]
     pub STRING_FROM_UTF8_AS_BYTES,
     complexity,
     "casting string slices to byte slices and back"
@@ -335,6 +376,7 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
     /// // example code which does not raise clippy warning
     /// let _ = "str".to_owned();
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub STR_TO_STRING,
     restriction,
     "using `to_string()` on a `&str`, which should be `to_owned()`"
@@ -384,6 +426,7 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'_>) {
     /// let msg = String::from("Hello World");
     /// let _ = msg.clone();
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub STRING_TO_STRING,
     restriction,
     "using `to_string()` on a `String`, which should be `clone()`"