Fix #277

Author: CppCXY

crates/emmylua_code_analysis/src/compilation/analyzer/flow/var_analyze.rs

@@ -420,8 +420,12 @@ fn infer_lua_type_assert(
 ) -> Option<()> {
     let binary_expr = call_expr.get_parent::<LuaBinaryExpr>()?;
     let op = binary_expr.get_op_token()?;
+    let mut is_eq = true;
     match op.get_op() {
         BinaryOperator::OpEq => {}
+        BinaryOperator::OpNe => {
+            is_eq = false;
+        }
         _ => return None,
     };
 
@@ -439,7 +443,7 @@ fn infer_lua_type_assert(
         _ => return None,
     };
 
-    let type_assert = match type_literal.as_str() {
+    let mut type_assert = match type_literal.as_str() {
         "number" => TypeAssertion::Narrow(LuaType::Number),
         "string" => TypeAssertion::Narrow(LuaType::String),
         "boolean" => TypeAssertion::Narrow(LuaType::Boolean),
@@ -452,6 +456,10 @@ fn infer_lua_type_assert(
         str => TypeAssertion::Narrow(LuaType::Ref(LuaTypeDeclId::new(str))),
     };
 
+    if !is_eq {
+        type_assert = type_assert.get_negation()?;
+    }
+
     broadcast_up(
         db,
         flow_chain,

crates/emmylua_code_analysis/src/compilation/test/flow.rs

@@ -321,4 +321,26 @@ end
         let d_desc = ws.humanize_type(d);
         assert_eq!(d_desc, "string");
     }
+
+    #[test]
+    fn test_issue_277() {
+        let mut ws = VirtualWorkspace::new();
+
+        ws.def(
+            r#"
+        ---@param t? table
+        function myfun3(t)
+            if type(t) ~= 'table' then
+                return
+            end
+
+            a = t
+        end   
+        "#,
+        );
+
+        let a = ws.expr_ty("a");
+        let a_desc = ws.humanize_type(a);
+        assert_eq!(a_desc, "table");
+    }
 }

crates/emmylua_code_analysis/src/db_index/type/type_assert.rs

@@ -20,6 +20,7 @@ impl TypeAssertion {
             TypeAssertion::Exist => Some(TypeAssertion::NotExist),
             TypeAssertion::NotExist => Some(TypeAssertion::Exist),
             TypeAssertion::Narrow(t) => Some(TypeAssertion::Remove(t.clone())),
+            TypeAssertion::Remove(t) => Some(TypeAssertion::Narrow(t.clone())),
             _ => None,
         }
     }