fix(es/minifier): Make array.join optimization more conservative

Only allow optimization for literals (string, number, null) and pure undefined.
All other expressions (identifiers, function calls, member expressions, etc.)
can potentially be null/undefined and should prevent optimization.

Co-authored-by: Donny/강동윤 <[email protected]>

Author: claude[bot]

crates/swc_ecma_minifier/src/compress/pure/misc.rs

@@ -563,10 +563,7 @@ impl Pure<'_> {
                 .any(|v| match &*v.expr {
                     e if is_pure_undefined(self.expr_ctx, e) => false,
                     Expr::Lit(lit) => !matches!(lit, Lit::Str(..) | Lit::Num(..) | Lit::Null(..)),
-                    // This can change behavior if the value is `undefined` or `null`.
-                    Expr::Ident(..) => false,
-                    Expr::OptChain(..) => false,
-                    Expr::Member(..) => false,
+                    // All other expressions can potentially be null/undefined
                     _ => true,
                 })
             {

crates/swc_ecma_minifier/tests/fixture/issues/10936/input.js

@@ -17,4 +17,16 @@ const test1 = [1, null, 2].join('');
 const test2 = [1, undefined, 2].join('');
 const test3 = [1, variable?.notExist, 2].join('');
 const test4 = [1, variable.data?.value, 2].join('');
-const test5 = [1, obj?.a?.b?.c, 2].join('');
+const test5 = [1, obj?.a?.b?.c, 2].join('');
+
+// Function calls can return null/undefined
+const test6 = [1, someFunction(), 2].join('');
+const test7 = [1, obj.method(), 2].join('');
+
+// Identifiers can be null/undefined  
+const test8 = [1, unknownVar, 2].join('');
+
+// Other expressions that can be null/undefined
+const test9 = [1, condition ? null : 'x', 2].join('');
+const test10 = [1, await promise, 2].join('');
+const test11 = [1, new Constructor(), 2].join('');