feat(core): created linter for #426

harper-core/src/linting/let_us_redundancy.rs

@@ -0,0 +1,55 @@
+use crate::{
+    patterns::{Pattern, SequencePattern, WordSet},
+    Token, TokenStringExt,
+};
+
+use super::{Lint, LintKind, PatternLinter, Suggestion};
+
+pub struct LetUsRedundancy {
+    pattern: Box<dyn Pattern>,
+}
+
+impl Default for LetUsRedundancy {
+    fn default() -> Self {
+        let pattern = SequencePattern::aco("let's")
+            .then_whitespace()
+            .then_word_set(WordSet::all(&["us", "me"]));
+
+        Self {
+            pattern: Box::new(pattern),
+        }
+    }
+}
+
+impl PatternLinter for LetUsRedundancy {
+    fn pattern(&self) -> &dyn Pattern {
+        self.pattern.as_ref()
+    }
+
+    fn match_to_lint(&self, matched_tokens: &[Token], _source: &[char]) -> Lint {
+        Lint {
+            span: matched_tokens[1..3].span().unwrap(),
+            lint_kind: LintKind::Repetition,
+            suggestions: vec![Suggestion::Remove],
+            message: "`let's` stands for `let us`, so including another pronoun is redundant."
+                .to_owned(),
+            priority: 31,
+        }
+    }
+
+    fn description(&self) -> &'static str {
+        "Many are not aware that the contraction `let's` is short for `let us`. As a result, many will incorrectly use it before a pronoun, such as in the phrase `let's us do`."
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::linting::tests::assert_suggestion_result;
+
+    use super::LetUsRedundancy;
+
+    #[test]
+    fn issue_426() {
+        assert_suggestion_result("let's us do", LetUsRedundancy::default(), "let's do");
+    }
+}

harper-core/src/linting/lint_group.rs

@@ -8,6 +8,7 @@ use super::capitalize_personal_pronouns::CapitalizePersonalPronouns;
 use super::correct_number_suffix::CorrectNumberSuffix;
 use super::dot_initialisms::DotInitialisms;
 use super::ellipsis_length::EllipsisLength;
+use super::let_us_redundancy::LetUsRedundancy;
 use super::linking_verbs::LinkingVerbs;
 use super::long_sentences::LongSentences;
 use super::matcher::Matcher;
@@ -187,7 +188,8 @@ create_lint_group_config!(
     PluralConjugate => false,
     OxfordComma => true,
     PronounContraction => true,
-    CurrencyPlacement => true
+    CurrencyPlacement => true,
+    LetUsRedundancy => true
 );
 
 impl<T: Dictionary + Default> Default for LintGroup<T> {

harper-core/src/linting/mod.rs

@@ -7,6 +7,7 @@ mod currency_placement;
 mod dashes;
 mod dot_initialisms;
 mod ellipsis_length;
+mod let_us_redundancy;
 mod linking_verbs;
 mod lint;
 mod lint_group;
@@ -40,6 +41,7 @@ pub use correct_number_suffix::CorrectNumberSuffix;
 pub use currency_placement::CurrencyPlacement;
 pub use dot_initialisms::DotInitialisms;
 pub use ellipsis_length::EllipsisLength;
+pub use let_us_redundancy::LetUsRedundancy;
 pub use linking_verbs::LinkingVerbs;
 pub use lint::{Lint, LintKind, Suggestion};
 pub use lint_group::{LintGroup, LintGroupConfig};