Implement mixed script confusable lint.

8 files changed, 206 insertions, 12 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 0c1c533f395..e05439d71e7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5405,15 +5405,15 @@ dependencies = [
 
 [[package]]
 name = "unicode-script"
-version = "0.4.0"
+version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5b2c5c29e805da6817f5af6a627d65adb045cebf05cccd5a3493d6109454391c"
+checksum = "58b33414ea8db4b7ea0343548dbdc31d27aef06beacf7044a87e564d9b0feb7d"
 
 [[package]]
 name = "unicode-security"
-version = "0.0.3"
+version = "0.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a5f9011bbed9c13372bc8df618b55a38138445199caf3b61d432c6859c36dee0"
+checksum = "5d87c28edc5b263377e448d6cdcb935c06b95413d8013ba6fae470558ccab18f"
 dependencies = [
  "unicode-normalization",
  "unicode-script",
diff --git a/src/librustc_lint/Cargo.toml b/src/librustc_lint/Cargo.toml
index ada6f2a9381..58c15257326 100644
--- a/src/librustc_lint/Cargo.toml
+++ b/src/librustc_lint/Cargo.toml
@@ -10,7 +10,7 @@ path = "lib.rs"
 
 [dependencies]
 log = "0.4"
-unicode-security = "0.0.3"
+unicode-security = "0.0.5"
 rustc_middle = { path = "../librustc_middle" }
 rustc_ast_pretty = { path = "../librustc_ast_pretty" }
 rustc_attr = { path = "../librustc_attr" }
diff --git a/src/librustc_lint/non_ascii_idents.rs b/src/librustc_lint/non_ascii_idents.rs
index 90bd7ad4acf..30dbd069c29 100644
--- a/src/librustc_lint/non_ascii_idents.rs
+++ b/src/librustc_lint/non_ascii_idents.rs
@@ -24,12 +24,20 @@ declare_lint! {
     crate_level_only
 }
 
-declare_lint_pass!(NonAsciiIdents => [NON_ASCII_IDENTS, UNCOMMON_CODEPOINTS, CONFUSABLE_IDENTS]);
+declare_lint! {
+    pub MIXED_SCRIPT_CONFUSABLES,
+    Warn,
+    "detects Unicode scripts whose mixed script confusables codepoints are solely used",
+    crate_level_only
+}
+
+declare_lint_pass!(NonAsciiIdents => [NON_ASCII_IDENTS, UNCOMMON_CODEPOINTS, CONFUSABLE_IDENTS, MIXED_SCRIPT_CONFUSABLES]);
 
 impl EarlyLintPass for NonAsciiIdents {
     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
         use rustc_session::lint::Level;
         use rustc_span::Span;
+        use std::collections::BTreeMap;
         use unicode_security::GeneralSecurityProfile;
         use utils::CowBoxSymStr;
 
@@ -37,8 +45,14 @@ impl EarlyLintPass for NonAsciiIdents {
         let check_uncommon_codepoints =
             cx.builder.lint_level(UNCOMMON_CODEPOINTS).0 != Level::Allow;
         let check_confusable_idents = cx.builder.lint_level(CONFUSABLE_IDENTS).0 != Level::Allow;
+        let check_mixed_script_confusables =
+            cx.builder.lint_level(MIXED_SCRIPT_CONFUSABLES).0 != Level::Allow;
 
-        if !check_non_ascii_idents && !check_uncommon_codepoints && !check_confusable_idents {
+        if !check_non_ascii_idents
+            && !check_uncommon_codepoints
+            && !check_confusable_idents
+            && !check_mixed_script_confusables
+        {
             return;
         }
 
@@ -107,6 +121,115 @@ impl EarlyLintPass for NonAsciiIdents {
                     .or_insert((symbol_str, sp, is_ascii));
             }
         }
+
+        if has_non_ascii_idents && check_mixed_script_confusables {
+            use unicode_security::is_potential_mixed_script_confusable_char;
+            use unicode_security::mixed_script::AugmentedScriptSet;
+
+            #[derive(Clone)]
+            enum ScriptSetUsage {
+                Suspicious(Vec<char>, Span),
+                Verified,
+            }
+
+            let mut script_states: FxHashMap<AugmentedScriptSet, ScriptSetUsage> =
+                FxHashMap::default();
+            let latin_augmented_script_set = AugmentedScriptSet::for_char('A');
+            script_states.insert(latin_augmented_script_set, ScriptSetUsage::Verified);
+
+            let mut has_suspicous = false;
+            for (symbol, &sp) in symbols.iter() {
+                let symbol_str = symbol.as_str();
+                for ch in symbol_str.chars() {
+                    if ch.is_ascii() {
+                        // all ascii characters are covered by exception.
+                        continue;
+                    }
+                    if !GeneralSecurityProfile::identifier_allowed(ch) {
+                        // this character is covered by `uncommon_codepoints` lint.
+                        continue;
+                    }
+                    let augmented_script_set = AugmentedScriptSet::for_char(ch);
+                    script_states
+                        .entry(augmented_script_set)
+                        .and_modify(|existing_state| {
+                            if let ScriptSetUsage::Suspicious(ch_list, _) = existing_state {
+                                if is_potential_mixed_script_confusable_char(ch) {
+                                    ch_list.push(ch);
+                                } else {
+                                    *existing_state = ScriptSetUsage::Verified;
+                                }
+                            }
+                        })
+                        .or_insert_with(|| {
+                            if !is_potential_mixed_script_confusable_char(ch) {
+                                ScriptSetUsage::Verified
+                            } else {
+                                has_suspicous = true;
+                                ScriptSetUsage::Suspicious(vec![ch], sp)
+                            }
+                        });
+                }
+            }
+
+            if has_suspicous {
+                let verified_augmented_script_sets = script_states
+                    .iter()
+                    .flat_map(|(k, v)| match v {
+                        ScriptSetUsage::Verified => Some(*k),
+                        _ => None,
+                    })
+                    .collect::<Vec<_>>();
+
+                // we're sorting the output here.
+                let mut lint_reports: BTreeMap<(Span, Vec<char>), AugmentedScriptSet> =
+                    BTreeMap::new();
+
+                'outerloop: for (augment_script_set, usage) in script_states {
+                    let (mut ch_list, sp) = match usage {
+                        ScriptSetUsage::Verified => continue,
+                        ScriptSetUsage::Suspicious(ch_list, sp) => (ch_list, sp),
+                    };
+
+                    if augment_script_set.is_all() {
+                        continue;
+                    }
+
+                    for existing in verified_augmented_script_sets.iter() {
+                        if existing.is_all() {
+                            continue;
+                        }
+                        let mut intersect = *existing;
+                        intersect.intersect_with(augment_script_set);
+                        if !intersect.is_empty() && !intersect.is_all() {
+                            continue 'outerloop;
+                        }
+                    }
+
+                    ch_list.sort();
+                    ch_list.dedup();
+                    lint_reports.insert((sp, ch_list), augment_script_set);
+                }
+
+                for ((sp, ch_list), script_set) in lint_reports {
+                    cx.struct_span_lint(MIXED_SCRIPT_CONFUSABLES, sp, |lint| {
+                        let message = format!(
+                            "The usage of Script Group `{}` in this crate consists solely of mixed script confusables",
+                            script_set);
+                        let mut note = "The usage includes ".to_string();
+                        for (idx, ch) in ch_list.into_iter().enumerate() {
+                            if idx != 0 {
+                                note += ", ";
+                            }
+                            let char_info = format!("'{}' (U+{:04X})", ch, ch as u32);
+                            note += &char_info;
+                        }
+                        note += ".";
+                        lint.build(&message).note(&note).note("Please recheck to make sure their usages are indeed what you want.").emit()
+                    });
+                }
+            }
+        }
     }
 }
 
diff --git a/src/test/ui/lint/rfc-2457-non-ascii-idents/lint-mixed-script-confusables-2.rs b/src/test/ui/lint/rfc-2457-non-ascii-idents/lint-mixed-script-confusables-2.rs
new file mode 100644
index 00000000000..a5b45466da5
--- /dev/null
+++ b/src/test/ui/lint/rfc-2457-non-ascii-idents/lint-mixed-script-confusables-2.rs
@@ -0,0 +1,20 @@
+// check-pass
+#![feature(non_ascii_idents)]
+#![deny(mixed_script_confusables)]
+
+struct ΑctuallyNotLatin;
+
+fn main() {
+    let λ = 42; // this usage of Greek confirms that Greek is used intentionally.
+}
+
+mod роре {
+    const エ: &'static str = "アイウ";
+
+    // this usage of Katakana confirms that Katakana is used intentionally.
+    fn ニャン() {
+        let д: usize = 100; // this usage of Cyrillic confirms that Cyrillic is used intentionally.
+
+        println!("meow!");
+    }
+}
diff --git a/src/test/ui/lint/rfc-2457-non-ascii-idents/lint-mixed-script-confusables.rs b/src/test/ui/lint/rfc-2457-non-ascii-idents/lint-mixed-script-confusables.rs
new file mode 100644
index 00000000000..4637b03f250
--- /dev/null
+++ b/src/test/ui/lint/rfc-2457-non-ascii-idents/lint-mixed-script-confusables.rs
@@ -0,0 +1,15 @@
+#![feature(non_ascii_idents)]
+#![deny(mixed_script_confusables)]
+
+struct ΑctuallyNotLatin;
+//~^ ERROR The usage of Script Group `Greek` in this crate consists solely of
+
+fn main() {
+    let v = ΑctuallyNotLatin;
+}
+
+mod роре {
+//~^ ERROR The usage of Script Group `Cyrillic` in this crate consists solely of
+    const エ: &'static str = "アイウ";
+    //~^ ERROR The usage of Script Group `Japanese, Katakana` in this crate consists solely of
+}
diff --git a/src/test/ui/lint/rfc-2457-non-ascii-idents/lint-mixed-script-confusables.stderr b/src/test/ui/lint/rfc-2457-non-ascii-idents/lint-mixed-script-confusables.stderr
new file mode 100644
index 00000000000..6f75a1ece37
--- /dev/null
+++ b/src/test/ui/lint/rfc-2457-non-ascii-idents/lint-mixed-script-confusables.stderr
@@ -0,0 +1,34 @@
+error: The usage of Script Group `Greek` in this crate consists solely of mixed script confusables
+  --> $DIR/lint-mixed-script-confusables.rs:4:8
+   |
+LL | struct ΑctuallyNotLatin;
+   |        ^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/lint-mixed-script-confusables.rs:2:9
+   |
+LL | #![deny(mixed_script_confusables)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: The usage includes 'Α' (U+0391).
+   = note: Please recheck to make sure their usages are indeed what you want.
+
+error: The usage of Script Group `Cyrillic` in this crate consists solely of mixed script confusables
+  --> $DIR/lint-mixed-script-confusables.rs:11:5
+   |
+LL | mod роре {
+   |     ^^^^
+   |
+   = note: The usage includes 'е' (U+0435), 'о' (U+043E), 'р' (U+0440).
+   = note: Please recheck to make sure their usages are indeed what you want.
+
+error: The usage of Script Group `Japanese, Katakana` in this crate consists solely of mixed script confusables
+  --> $DIR/lint-mixed-script-confusables.rs:13:11
+   |
+LL |     const エ: &'static str = "アイウ";
+   |           ^^
+   |
+   = note: The usage includes 'エ' (U+30A8).
+   = note: Please recheck to make sure their usages are indeed what you want.
+
+error: aborting due to 3 previous errors
+
diff --git a/src/test/ui/utf8_idents.rs b/src/test/ui/utf8_idents.rs
index f59d5502aae..6c54086cc20 100644
--- a/src/test/ui/utf8_idents.rs
+++ b/src/test/ui/utf8_idents.rs
@@ -1,3 +1,5 @@
+#![allow(mixed_script_confusables)]
+
 fn foo<
     'β, //~ ERROR non-ascii idents are not fully supported
     γ  //~ ERROR non-ascii idents are not fully supported
diff --git a/src/test/ui/utf8_idents.stderr b/src/test/ui/utf8_idents.stderr
index 877412df8fa..2fc0b1c39ef 100644
--- a/src/test/ui/utf8_idents.stderr
+++ b/src/test/ui/utf8_idents.stderr
@@ -1,5 +1,5 @@
 error[E0658]: non-ascii idents are not fully supported
-  --> $DIR/utf8_idents.rs:2:5
+  --> $DIR/utf8_idents.rs:4:5
    |
 LL |     'β,
    |     ^^
@@ -8,7 +8,7 @@ LL |     'β,
    = help: add `#![feature(non_ascii_idents)]` to the crate attributes to enable
 
 error[E0658]: non-ascii idents are not fully supported
-  --> $DIR/utf8_idents.rs:3:5
+  --> $DIR/utf8_idents.rs:5:5
    |
 LL |     γ
    |     ^
@@ -17,7 +17,7 @@ LL |     γ
    = help: add `#![feature(non_ascii_idents)]` to the crate attributes to enable
 
 error[E0658]: non-ascii idents are not fully supported
-  --> $DIR/utf8_idents.rs:8:5
+  --> $DIR/utf8_idents.rs:10:5
    |
 LL |     δ: usize
    |     ^
@@ -26,7 +26,7 @@ LL |     δ: usize
    = help: add `#![feature(non_ascii_idents)]` to the crate attributes to enable
 
 error[E0658]: non-ascii idents are not fully supported
-  --> $DIR/utf8_idents.rs:12:9
+  --> $DIR/utf8_idents.rs:14:9
    |
 LL |     let α = 0.00001f64;
    |         ^
@@ -35,7 +35,7 @@ LL |     let α = 0.00001f64;
    = help: add `#![feature(non_ascii_idents)]` to the crate attributes to enable
 
 warning: type parameter `γ` should have an upper camel case name
-  --> $DIR/utf8_idents.rs:3:5
+  --> $DIR/utf8_idents.rs:5:5
    |
 LL |     γ
    |     ^ help: convert the identifier to upper camel case: `Γ`