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fix(diagnostics): compare non-nil with nil #906

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17 changes: 17 additions & 0 deletions crates/emmylua_code_analysis/src/diagnostic/test/unnecessary_assert_test.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -127,4 +127,21 @@ mod test {
"#
));
}

#[test]
fn test_nonnli_with_nil() {
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@gemini-code-assist gemini-code-assist bot Dec 27, 2025

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medium

There's a typo in the test function name. It should be test_nonnil_with_nil to match the other test file and for clarity.

Suggested change
fn test_nonnli_with_nil() {
fn test_nonnil_with_nil() {

let mut ws = VirtualWorkspace::new();
assert!(!ws.check_code_for(
DiagnosticCode::UnnecessaryAssert,
r#"
assert("abc" ~= nil)
"#
));
assert!(!ws.check_code_for(
DiagnosticCode::UnnecessaryAssert,
r#"
assert(1 == nil)
"#
));
Comment on lines +134 to +145
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@gemini-code-assist gemini-code-assist bot Dec 27, 2025

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critical

The logic of these tests is incorrect. With the changes in infer_binary/mod.rs, the expressions inside assert() will be evaluated as constant booleans (true for "abc" ~= nil and false for 1 == nil). This should trigger the UnnecessaryAssert diagnostic for both cases (an unnecessary and an impossible assert, respectively).

Therefore, ws.check_code_for(...) should return true, and you should be using assert!(...) to verify that the diagnostic is correctly reported.

Suggested change
assert!(!ws.check_code_for(
DiagnosticCode::UnnecessaryAssert,
r#"
assert("abc" ~= nil)
"#
));
assert!(!ws.check_code_for(
DiagnosticCode::UnnecessaryAssert,
r#"
assert(1 == nil)
"#
));
assert!(ws.check_code_for(
DiagnosticCode::UnnecessaryAssert,
r#"
assert("abc" ~= nil)
"#
));
assert!(ws.check_code_for(
DiagnosticCode::UnnecessaryAssert,
r#"
assert(1 == nil)
"#
));

}
}
21 changes: 21 additions & 0 deletions crates/emmylua_code_analysis/src/diagnostic/test/unnecessary_if_test.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,4 +26,25 @@ mod test {
"#
));
}

#[test]
fn test_nonnil_with_nil() {
let mut ws = VirtualWorkspace::new();
assert!(!ws.check_code_for(
DiagnosticCode::UnnecessaryIf,
r#"
if 1 ~= nil then
error("Impossible")
end
"#
));
assert!(!ws.check_code_for(
DiagnosticCode::UnnecessaryIf,
r#"
if "abc" == nil then
error("Impossible")
end
"#
));
Comment on lines +33 to +48
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@gemini-code-assist gemini-code-assist bot Dec 27, 2025

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critical

The logic of these tests is incorrect. With the changes in infer_binary/mod.rs, the conditions in the if statements will be evaluated as constant booleans (true for 1 ~= nil and false for "abc" == nil). This should trigger the UnnecessaryIf diagnostic for both cases (an unnecessary and an impossible if-condition, respectively).

Therefore, ws.check_code_for(...) should return true, and you should be using assert!(...) to verify that the diagnostic is correctly reported.

Suggested change
assert!(!ws.check_code_for(
DiagnosticCode::UnnecessaryIf,
r#"
if 1 ~= nil then
error("Impossible")
end
"#
));
assert!(!ws.check_code_for(
DiagnosticCode::UnnecessaryIf,
r#"
if "abc" == nil then
error("Impossible")
end
"#
));
assert!(ws.check_code_for(
DiagnosticCode::UnnecessaryIf,
r#"
if 1 ~= nil then
error("Impossible")
end
"#
));
assert!(ws.check_code_for(
DiagnosticCode::UnnecessaryIf,
r#"
if "abc" == nil then
error("Impossible")
end
"#
));

}
}
10 changes: 10 additions & 0 deletions crates/emmylua_code_analysis/src/semantic/infer/infer_binary/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -506,6 +506,16 @@ fn infer_cmp_expr(_: &DbIndex, left: LuaType, right: LuaType, op: BinaryOperator
BinaryOperator::OpNe => Ok(LuaType::BooleanConst(i != j)),
_ => Ok(LuaType::Boolean),
},
(LuaType::Nil, right) if right.is_const() => match op {
BinaryOperator::OpEq => Ok(LuaType::BooleanConst(false)),
BinaryOperator::OpNe => Ok(LuaType::BooleanConst(true)),
_ => Ok(LuaType::Boolean),
},
(left, LuaType::Nil) if left.is_const() => match op {
BinaryOperator::OpEq => Ok(LuaType::BooleanConst(false)),
BinaryOperator::OpNe => Ok(LuaType::BooleanConst(true)),
_ => Ok(LuaType::Boolean),
},
Comment on lines +509 to +518
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medium

These two match arms handle the cases (nil, const) and (const, nil) respectively, and their logic is identical. You can combine them into a single arm to reduce code duplication and improve maintainability.

Suggested change
(LuaType::Nil, right) if right.is_const() => match op {
BinaryOperator::OpEq => Ok(LuaType::BooleanConst(false)),
BinaryOperator::OpNe => Ok(LuaType::BooleanConst(true)),
_ => Ok(LuaType::Boolean),
},
(left, LuaType::Nil) if left.is_const() => match op {
BinaryOperator::OpEq => Ok(LuaType::BooleanConst(false)),
BinaryOperator::OpNe => Ok(LuaType::BooleanConst(true)),
_ => Ok(LuaType::Boolean),
},
(left, right) if (left.is_nil() && right.is_const()) || (right.is_nil() && left.is_const()) => match op {
BinaryOperator::OpEq => Ok(LuaType::BooleanConst(false)),
BinaryOperator::OpNe => Ok(LuaType::BooleanConst(true)),
_ => Ok(LuaType::Boolean),
},

(left, right) if left.is_const() && right.is_const() => Ok(LuaType::BooleanConst(false)),
_ => Ok(LuaType::Boolean),
}
Expand Down