fix(linter/const-comparisons): detect equality contradictions

crates/oxc_linter/src/rules/oxc/const_comparisons.rs

@@ -61,17 +61,35 @@ fn identical_expressions_logical_operator(left_span: Span, right_span: Span) ->
                     ])
 }
 
-fn identical_expressions_logical_operator_negated(
+fn equivalent_expressions_logical_operator(left_span: Span, right_span: Span) -> OxcDiagnostic {
+    OxcDiagnostic::warn("Both sides of the logical operator are equivalent")
+        .with_help("This logical expression will always evaluate to the same value as either side.")
+        .with_labels([
+            left_span.label("If this expression evaluates to true"),
+            right_span.label("This equivalent expression will always evaluate to true"),
+        ])
+}
+
+fn complementary_expressions_logical_operator(
     always_truthy: bool,
     left_span: Span,
     right_span: Span,
 ) -> OxcDiagnostic {
+    let (left_label, right_label) = if always_truthy {
+        ("If this expression evaluates to false", "This expression must evaluate to true")
+    } else {
+        ("If this expression evaluates to true", "This expression cannot also evaluate to true")
+    };
+
     OxcDiagnostic::warn("Unexpected constant comparison")
         .with_help(format!("This logical expression will always evaluate to {always_truthy}"))
-        .with_labels([
-            left_span.label("If this expression evaluates to true"),
-            right_span.label("This expression will never evaluate to true"),
-        ])
+        .with_labels([left_span.label(left_label), right_span.label(right_label)])
+}
+
+#[derive(Clone, Copy)]
+enum EqualityRelation {
+    Equivalent,
+    Inverse,
 }
 
 /// <https://rust-lang.github.io/rust-clippy/master/index.html#/impossible>
@@ -246,6 +264,30 @@ impl ConstComparisons {
                 logical_expr.left.span(),
                 logical_expr.right.span(),
             ));
+            return;
+        }
+
+        if let Some(relation) = equality_relation(
+            logical_expr.left.get_inner_expression(),
+            logical_expr.right.get_inner_expression(),
+            ctx,
+        ) {
+            match relation {
+                EqualityRelation::Equivalent => {
+                    ctx.diagnostic(equivalent_expressions_logical_operator(
+                        logical_expr.left.span(),
+                        logical_expr.right.span(),
+                    ));
+                }
+                EqualityRelation::Inverse => {
+                    ctx.diagnostic(complementary_expressions_logical_operator(
+                        matches!(logical_expr.operator, LogicalOperator::Or),
+                        logical_expr.left.span(),
+                        logical_expr.right.span(),
+                    ));
+                }
+            }
+            return;
         }
 
         // if either are `!foo`, check whether it looks like `foo && !foo` or `foo || !foo`
@@ -256,7 +298,7 @@ impl ConstComparisons {
                 if negated_expr.operator == UnaryOperator::LogicalNot
                     && is_same_expression(&negated_expr.argument, other_expr, ctx)
                 {
-                    ctx.diagnostic(identical_expressions_logical_operator_negated(
+                    ctx.diagnostic(complementary_expressions_logical_operator(
                         matches!(logical_expr.operator, LogicalOperator::Or),
                         logical_expr.left.span(),
                         logical_expr.right.span(),
@@ -361,6 +403,51 @@ fn comparison_to_const<'a, 'b>(
     None
 }
 
+fn equality_relation(
+    left: &Expression,
+    right: &Expression,
+    ctx: &LintContext,
+) -> Option<EqualityRelation> {
+    if let Expression::BinaryExpression(left_bin_expr) = left
+        && let Expression::BinaryExpression(right_bin_expr) = right
+        && left_bin_expr.operator.is_equality()
+        && right_bin_expr.operator.is_equality()
+    {
+        let same_order = is_same_expression(
+            left_bin_expr.left.get_inner_expression(),
+            right_bin_expr.left.get_inner_expression(),
+            ctx,
+        ) && is_same_expression(
+            left_bin_expr.right.get_inner_expression(),
+            right_bin_expr.right.get_inner_expression(),
+            ctx,
+        );
+        let swapped_order = is_same_expression(
+            left_bin_expr.left.get_inner_expression(),
+            right_bin_expr.right.get_inner_expression(),
+            ctx,
+        ) && is_same_expression(
+            left_bin_expr.right.get_inner_expression(),
+            right_bin_expr.left.get_inner_expression(),
+            ctx,
+        );
+
+        if !same_order && !swapped_order {
+            return None;
+        }
+
+        if left_bin_expr.operator == right_bin_expr.operator {
+            return Some(EqualityRelation::Equivalent);
+        } else if left_bin_expr.operator.equality_inverse_operator()
+            == Some(right_bin_expr.operator)
+        {
+            return Some(EqualityRelation::Inverse);
+        }
+    }
+
+    None
+}
+
 fn all_and_comparison_to_const<'a, 'b>(
     expr: &'b Expression<'a>,
 ) -> Box<dyn Iterator<Item = (CmpOp, &'b Expression<'a>, &'b NumericLiteral<'a>, Span)> + 'b> {
@@ -590,13 +677,21 @@ fn test() {
         "a.b.c >= a.b.c",
         "a == b && a == b",
         "a == b || a == b",
+        "a == b && b == a",
+        "a == (b) && (b) == a",
+        "a != b || b != a",
         "!foo && !foo",
         "!foo || !foo",
         "class Foo { #a; #b; constructor() { this.#a = 1; }; test() { return this.#a > this.#a } }",
         "!foo && foo",
         "foo && !foo",
         "!foo || foo",
         "foo || !foo",
+        "a == b && a != b",
+        "a != b && b == a",
+        "a !== a && a === a",
+        "a === b || a !== b",
+        "a !== a || a === a",
         "let numOrUndefined: number | undefined = 6; if (numOrUndefined || 0 > 0) {}",
         "let numOrUndefined: number | undefined = 6; if (numOrUndefined ?? 0 > 0) {}",
     ];

crates/oxc_linter/src/snapshots/oxc_const_comparisons.snap

@@ -289,6 +289,33 @@ source: crates/oxc_linter/src/tester.rs
    ╰────
   help: This logical expression will always evaluate to the same value as the expression itself.
 
+  ⚠ oxc(const-comparisons): Both sides of the logical operator are equivalent
+   ╭─[const_comparisons.tsx:1:1]
+ 1 │ a == b && b == a
+   · ───┬──    ───┬──
+   ·    │         ╰── This equivalent expression will always evaluate to true
+   ·    ╰── If this expression evaluates to true
+   ╰────
+  help: This logical expression will always evaluate to the same value as either side.
+
+  ⚠ oxc(const-comparisons): Both sides of the logical operator are equivalent
+   ╭─[const_comparisons.tsx:1:1]
+ 1 │ a == (b) && (b) == a
+   · ────┬───    ────┬───
+   ·     │           ╰── This equivalent expression will always evaluate to true
+   ·     ╰── If this expression evaluates to true
+   ╰────
+  help: This logical expression will always evaluate to the same value as either side.
+
+  ⚠ oxc(const-comparisons): Both sides of the logical operator are equivalent
+   ╭─[const_comparisons.tsx:1:1]
+ 1 │ a != b || b != a
+   · ───┬──    ───┬──
+   ·    │         ╰── This equivalent expression will always evaluate to true
+   ·    ╰── If this expression evaluates to true
+   ╰────
+  help: This logical expression will always evaluate to the same value as either side.
+
   ⚠ oxc(const-comparisons): Both sides of the logical operator are the same
    ╭─[const_comparisons.tsx:1:1]
  1 │ !foo && !foo
@@ -318,7 +345,7 @@ source: crates/oxc_linter/src/tester.rs
    ╭─[const_comparisons.tsx:1:1]
  1 │ !foo && foo
    · ──┬─    ─┬─
-   ·   │      ╰── This expression will never evaluate to true
+   ·   │      ╰── This expression cannot also evaluate to true
    ·   ╰── If this expression evaluates to true
    ╰────
   help: This logical expression will always evaluate to false
@@ -327,7 +354,7 @@ source: crates/oxc_linter/src/tester.rs
    ╭─[const_comparisons.tsx:1:1]
  1 │ foo && !foo
    · ─┬─    ──┬─
-   ·  │       ╰── This expression will never evaluate to true
+   ·  │       ╰── This expression cannot also evaluate to true
    ·  ╰── If this expression evaluates to true
    ╰────
   help: This logical expression will always evaluate to false
@@ -336,17 +363,62 @@ source: crates/oxc_linter/src/tester.rs
    ╭─[const_comparisons.tsx:1:1]
  1 │ !foo || foo
    · ──┬─    ─┬─
-   ·   │      ╰── This expression will never evaluate to true
-   ·   ╰── If this expression evaluates to true
+   ·   │      ╰── This expression must evaluate to true
+   ·   ╰── If this expression evaluates to false
    ╰────
   help: This logical expression will always evaluate to true
 
   ⚠ oxc(const-comparisons): Unexpected constant comparison
    ╭─[const_comparisons.tsx:1:1]
  1 │ foo || !foo
    · ─┬─    ──┬─
-   ·  │       ╰── This expression will never evaluate to true
-   ·  ╰── If this expression evaluates to true
+   ·  │       ╰── This expression must evaluate to true
+   ·  ╰── If this expression evaluates to false
+   ╰────
+  help: This logical expression will always evaluate to true
+
+  ⚠ oxc(const-comparisons): Unexpected constant comparison
+   ╭─[const_comparisons.tsx:1:1]
+ 1 │ a == b && a != b
+   · ───┬──    ───┬──
+   ·    │         ╰── This expression cannot also evaluate to true
+   ·    ╰── If this expression evaluates to true
+   ╰────
+  help: This logical expression will always evaluate to false
+
+  ⚠ oxc(const-comparisons): Unexpected constant comparison
+   ╭─[const_comparisons.tsx:1:1]
+ 1 │ a != b && b == a
+   · ───┬──    ───┬──
+   ·    │         ╰── This expression cannot also evaluate to true
+   ·    ╰── If this expression evaluates to true
+   ╰────
+  help: This logical expression will always evaluate to false
+
+  ⚠ oxc(const-comparisons): Unexpected constant comparison
+   ╭─[const_comparisons.tsx:1:1]
+ 1 │ a !== a && a === a
+   · ───┬───    ───┬───
+   ·    │          ╰── This expression cannot also evaluate to true
+   ·    ╰── If this expression evaluates to true
+   ╰────
+  help: This logical expression will always evaluate to false
+
+  ⚠ oxc(const-comparisons): Unexpected constant comparison
+   ╭─[const_comparisons.tsx:1:1]
+ 1 │ a === b || a !== b
+   · ───┬───    ───┬───
+   ·    │          ╰── This expression must evaluate to true
+   ·    ╰── If this expression evaluates to false
+   ╰────
+  help: This logical expression will always evaluate to true
+
+  ⚠ oxc(const-comparisons): Unexpected constant comparison
+   ╭─[const_comparisons.tsx:1:1]
+ 1 │ a !== a || a === a
+   · ───┬───    ───┬───
+   ·    │          ╰── This expression must evaluate to true
+   ·    ╰── If this expression evaluates to false
    ╰────
   help: This logical expression will always evaluate to true