Auto merge of #6105 - bugadani:sus-char, r=ebroto

Lint for invisible Unicode characters other than ZWSP

This PR extends the existing `zero_width_space` lint to look for other invisible characters as well (in this case, `\\u{ad}` soft hyphen.

I feel like this lint is the logical place to add the check, but I also realize the lint name is not particularly flexible, but I also understand that it shouldn't be renamed for compatibility reasons.

Open questions:
 - What other characters should trigger the lint?
 - What should be done with the lint name?
 - How to indicate the change in functionality?

Motivation behind this PR: rust-lang/rust#77417 - I managed to shoot myself in the foot by an invisible character pasted into my test case.

Author: bors

CHANGELOG.md

@@ -1647,6 +1647,7 @@ Released 2018-09-13
 [`invalid_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#invalid_ref
 [`invalid_regex`]: https://rust-lang.github.io/rust-clippy/master/index.html#invalid_regex
 [`invalid_upcast_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#invalid_upcast_comparisons
+[`invisible_characters`]: https://rust-lang.github.io/rust-clippy/master/index.html#invisible_characters
 [`items_after_statements`]: https://rust-lang.github.io/rust-clippy/master/index.html#items_after_statements
 [`iter_cloned_collect`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_cloned_collect
 [`iter_next_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_next_loop
@@ -1922,6 +1923,5 @@ Released 2018-09-13
 [`zero_divided_by_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_divided_by_zero
 [`zero_prefixed_literal`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_prefixed_literal
 [`zero_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_ptr
-[`zero_width_space`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_width_space
 [`zst_offset`]: https://rust-lang.github.io/rust-clippy/master/index.html#zst_offset
 <!-- end autogenerated links to lint list -->

clippy_lints/src/lib.rs

@@ -854,9 +854,9 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         &types::UNIT_CMP,
         &types::UNNECESSARY_CAST,
         &types::VEC_BOX,
+        &unicode::INVISIBLE_CHARACTERS,
         &unicode::NON_ASCII_LITERAL,
         &unicode::UNICODE_NOT_NFC,
-        &unicode::ZERO_WIDTH_SPACE,
         &unit_return_expecting_ord::UNIT_RETURN_EXPECTING_ORD,
         &unnamed_address::FN_ADDRESS_COMPARISONS,
         &unnamed_address::VTABLE_ADDRESS_COMPARISONS,
@@ -1511,7 +1511,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&types::UNIT_CMP),
         LintId::of(&types::UNNECESSARY_CAST),
         LintId::of(&types::VEC_BOX),
-        LintId::of(&unicode::ZERO_WIDTH_SPACE),
+        LintId::of(&unicode::INVISIBLE_CHARACTERS),
         LintId::of(&unit_return_expecting_ord::UNIT_RETURN_EXPECTING_ORD),
         LintId::of(&unnamed_address::FN_ADDRESS_COMPARISONS),
         LintId::of(&unnamed_address::VTABLE_ADDRESS_COMPARISONS),
@@ -1779,7 +1779,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&types::ABSURD_EXTREME_COMPARISONS),
         LintId::of(&types::CAST_REF_TO_MUT),
         LintId::of(&types::UNIT_CMP),
-        LintId::of(&unicode::ZERO_WIDTH_SPACE),
+        LintId::of(&unicode::INVISIBLE_CHARACTERS),
         LintId::of(&unit_return_expecting_ord::UNIT_RETURN_EXPECTING_ORD),
         LintId::of(&unnamed_address::FN_ADDRESS_COMPARISONS),
         LintId::of(&unnamed_address::VTABLE_ADDRESS_COMPARISONS),
@@ -1910,6 +1910,7 @@ pub fn register_renamed(ls: &mut rustc_lint::LintStore) {
     ls.register_renamed("clippy::for_loop_over_option", "clippy::for_loops_over_fallibles");
     ls.register_renamed("clippy::for_loop_over_result", "clippy::for_loops_over_fallibles");
     ls.register_renamed("clippy::identity_conversion", "clippy::useless_conversion");
+    ls.register_renamed("clippy::zero_width_space", "clippy::invisible_characters");
 }
 
 // only exists to let the dogfood integration test works.

clippy_lints/src/unicode.rs

@@ -8,18 +8,18 @@ use rustc_span::source_map::Span;
 use unicode_normalization::UnicodeNormalization;
 
 declare_clippy_lint! {
-    /// **What it does:** Checks for the Unicode zero-width space in the code.
+    /// **What it does:** Checks for invisible Unicode characters in the code.
     ///
     /// **Why is this bad?** Having an invisible character in the code makes for all
     /// sorts of April fools, but otherwise is very much frowned upon.
     ///
     /// **Known problems:** None.
     ///
-    /// **Example:** You don't see it, but there may be a zero-width space
-    /// somewhere in this text.
-    pub ZERO_WIDTH_SPACE,
+    /// **Example:** You don't see it, but there may be a zero-width space or soft hyphen
+    /// some­where in this text.
+    pub INVISIBLE_CHARACTERS,
     correctness,
-    "using a zero-width space in a string literal, which is confusing"
+    "using an invisible character in a string literal, which is confusing"
 }
 
 declare_clippy_lint! {
@@ -63,7 +63,7 @@ declare_clippy_lint! {
     "using a Unicode literal not in NFC normal form (see [Unicode tr15](http://www.unicode.org/reports/tr15/) for further information)"
 }
 
-declare_lint_pass!(Unicode => [ZERO_WIDTH_SPACE, NON_ASCII_LITERAL, UNICODE_NOT_NFC]);
+declare_lint_pass!(Unicode => [INVISIBLE_CHARACTERS, NON_ASCII_LITERAL, UNICODE_NOT_NFC]);
 
 impl LateLintPass<'_> for Unicode {
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'_ Expr<'_>) {
@@ -91,14 +91,17 @@ fn escape<T: Iterator<Item = char>>(s: T) -> String {
 
 fn check_str(cx: &LateContext<'_>, span: Span, id: HirId) {
     let string = snippet(cx, span, "");
-    if string.contains('\u{200B}') {
+    if string.chars().any(|c| ['\u{200B}', '\u{ad}', '\u{2060}'].contains(&c)) {
         span_lint_and_sugg(
             cx,
-            ZERO_WIDTH_SPACE,
+            INVISIBLE_CHARACTERS,
             span,
-            "zero-width space detected",
+            "invisible character detected",
             "consider replacing the string with",
-            string.replace("\u{200B}", "\\u{200B}"),
+            string
+                .replace("\u{200B}", "\\u{200B}")
+                .replace("\u{ad}", "\\u{AD}")
+                .replace("\u{2060}", "\\u{2060}"),
             Applicability::MachineApplicable,
         );
     }

src/lintlist/mod.rs

@@ -969,6 +969,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
         deprecation: None,
         module: "types",
     },
+    Lint {
+        name: "invisible_characters",
+        group: "correctness",
+        desc: "using an invisible character in a string literal, which is confusing",
+        deprecation: None,
+        module: "unicode",
+    },
     Lint {
         name: "items_after_statements",
         group: "pedantic",
@@ -2810,13 +2817,6 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
         deprecation: None,
         module: "misc",
     },
-    Lint {
-        name: "zero_width_space",
-        group: "correctness",
-        desc: "using a zero-width space in a string literal, which is confusing",
-        deprecation: None,
-        module: "unicode",
-    },
     Lint {
         name: "zst_offset",
         group: "correctness",

tests/ui/unicode.rs

@@ -1,7 +1,11 @@
-#[warn(clippy::zero_width_space)]
+#[warn(clippy::invisible_characters)]
 fn zero() {
     print!("Here >​< is a ZWS, and ​another");
     print!("This\u{200B}is\u{200B}fine");
+    print!("Here >­< is a SHY, and ­another");
+    print!("This\u{ad}is\u{ad}fine");
+    print!("Here >⁠< is a WJ, and ⁠another");
+    print!("This\u{2060}is\u{2060}fine");
 }
 
 #[warn(clippy::unicode_not_nfc)]

tests/ui/unicode.stderr

@@ -1,26 +1,38 @@
-error: zero-width space detected
+error: invisible character detected
   --> $DIR/unicode.rs:3:12
    |
 LL |     print!("Here >​< is a ZWS, and ​another");
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing the string with: `"Here >/u{200B}< is a ZWS, and /u{200B}another"`
    |
-   = note: `-D clippy::zero-width-space` implied by `-D warnings`
+   = note: `-D clippy::invisible-characters` implied by `-D warnings`
+
+error: invisible character detected
+  --> $DIR/unicode.rs:5:12
+   |
+LL |     print!("Here >­< is a SHY, and ­another");
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing the string with: `"Here >/u{AD}< is a SHY, and /u{AD}another"`
+
+error: invisible character detected
+  --> $DIR/unicode.rs:7:12
+   |
+LL |     print!("Here >⁠< is a WJ, and ⁠another");
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing the string with: `"Here >/u{2060}< is a WJ, and /u{2060}another"`
 
 error: non-NFC Unicode sequence detected
-  --> $DIR/unicode.rs:9:12
+  --> $DIR/unicode.rs:13:12
    |
 LL |     print!("̀àh?");
    |            ^^^^^ help: consider replacing the string with: `"̀àh?"`
    |
    = note: `-D clippy::unicode-not-nfc` implied by `-D warnings`
 
 error: literal non-ASCII character detected
-  --> $DIR/unicode.rs:15:12
+  --> $DIR/unicode.rs:19:12
    |
 LL |     print!("Üben!");
    |            ^^^^^^^ help: consider replacing the string with: `"/u{dc}ben!"`
    |
    = note: `-D clippy::non-ascii-literal` implied by `-D warnings`
 
-error: aborting due to 3 previous errors
+error: aborting due to 5 previous errors