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feat(linter): implement @typescript-eslint/no-non-null-assertion (#3825)
Related issue: #2180 original implementation - code: https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/src/rules/no-non-null-assertion.ts - test: https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/tests/rules/no-non-null-assertion.test.ts - doc: https://typescript-eslint.io/rules/no-non-null-assertion/ typescript-eslint has a feature that is manually fixable by editor suggestions on this rule, but oxc does not have one as far as I know, so the implementation is simple compared to typescript-eslint
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‎crates/oxc_linter/src/rules.rs

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@@ -137,6 +137,7 @@ mod typescript {
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pub mod no_misused_new;
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pub mod no_namespace;
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pub mod no_non_null_asserted_optional_chain;
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pub mod no_non_null_assertion;
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pub mod no_this_alias;
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pub mod no_unnecessary_type_constraint;
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pub mod no_unsafe_declaration_merging;
@@ -540,6 +541,7 @@ oxc_macros::declare_all_lint_rules! {
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typescript::triple_slash_reference,
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typescript::prefer_literal_enum_member,
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typescript::explicit_function_return_type,
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typescript::no_non_null_assertion,
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jest::expect_expect,
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jest::max_expects,
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jest::max_nested_describe,

‎crates/oxc_linter/src/rules/typescript/no_non_null_assertion.rs

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@@ -0,0 +1,87 @@
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use oxc_ast::AstKind;
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use oxc_diagnostics::OxcDiagnostic;
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use oxc_macros::declare_oxc_lint;
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use oxc_span::Span;
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use crate::{context::LintContext, rule::Rule, AstNode};
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#[derive(Debug, Default, Clone)]
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pub struct NoNonNullAssertion;
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declare_oxc_lint!(
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/// ### What it does
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/// Disallow non-null assertions using the ! postfix operator.
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///
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/// ### Why is this bad?
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/// TypeScript's ! non-null assertion operator asserts to the type system that an expression is non-nullable, as in not null or undefined. Using assertions to tell the type system new information is often a sign that code is not fully type-safe. It's generally better to structure program logic so that TypeScript understands when values may be nullable.
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///
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/// ### Example
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/// ```javascript
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/// x!;
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/// x!.y;
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/// x.y!;
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/// ```
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NoNonNullAssertion,
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restriction,
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);
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fn no_non_null_assertion_diagnostic(span0: Span) -> OxcDiagnostic {
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OxcDiagnostic::warn("typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.")
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.with_help("Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.")
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.with_labels([span0.into()])
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}
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impl Rule for NoNonNullAssertion {
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fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
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let AstKind::TSNonNullExpression(expr) = node.kind() else { return };
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ctx.diagnostic(no_non_null_assertion_diagnostic(expr.span));
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}
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}
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#[test]
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fn test() {
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use crate::tester::Tester;
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let pass = vec!["x;", "x.y;", "x.y.z;", "x?.y.z;", "x?.y?.z;", "!x;"];
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let fail = vec![
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"x!;",
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"x!.y;",
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"x.y!;",
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"!x!.y;",
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"x!.y?.z;",
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"x![y];",
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"x![y]?.z;",
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"x.y.z!();",
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"x.y?.z!();",
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"x!!!;",
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"x!!.y;",
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"x.y!!;",
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"x.y.z!!();",
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"x!?.[y].z;",
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"x!?.y.z;",
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"x.y.z!?.();",
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"
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x!
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.y
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",
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"
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x!
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// comment
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.y
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",
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"
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x!
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// comment
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. /* comment */
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y
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",
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"
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x!
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// comment
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/* comment */ ['y']
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",
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];
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Tester::new(NoNonNullAssertion::NAME, pass, fail).test_and_snapshot();
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}

‎crates/oxc_linter/src/snapshots/no_non_null_assertion.snap

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---
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source: crates/oxc_linter/src/tester.rs
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---
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!;
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!.y;
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x.y!;
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· ────
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:2]
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1 │ !x!.y;
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!.y?.z;
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x![y];
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x![y]?.z;
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x.y.z!();
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· ──────
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x.y?.z!();
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· ───────
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!!!;
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· ────
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!!!;
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· ───
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!!!;
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!!.y;
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· ───
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!!.y;
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x.y!!;
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· ─────
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x.y!!;
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· ────
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x.y.z!!();
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· ───────
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x.y.z!!();
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· ──────
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!?.[y].z;
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x!?.y.z;
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· ──
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:1:1]
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1 │ x.y.z!?.();
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· ──────
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:2:10]
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1 │
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2 │ x!
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· ──
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3 │ .y
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:2:10]
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1 │
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2 │ x!
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· ──
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3 │ // comment
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:2:10]
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1 │
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2 │ x!
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· ──
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3 │ // comment
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.
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⚠ typescript-eslint(no-non-null-assertion): Forbidden non-null assertion.
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╭─[no_non_null_assertion.tsx:2:10]
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1 │
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2 │ x!
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· ──
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3 │ // comment
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╰────
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help: Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.

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