reduce: fix compile errors

Regressed by c11b6ad.

Author: jacobly0

lib/compiler/reduce/Walk.zig

@@ -345,19 +345,19 @@ fn walkExpression(w: *Walk, node: Ast.Node.Index) Error!void {
         },
 
         .assign_destructure => {
-            const full = tree.assignDestructure(node);
+            const full = ast.assignDestructure(node);
             for (full.ast.variables) |variable_node| {
-                switch (node_tags[lhs_node]) {
+                switch (node_tags[variable_node]) {
                     .global_var_decl,
                     .local_var_decl,
                     .simple_var_decl,
                     .aligned_var_decl,
-                    => try walkLocalVarDecl(w, ast.fullVarDecl(lhs_node).?),
+                    => try walkLocalVarDecl(w, ast.fullVarDecl(variable_node).?),
 
                     else => try walkExpression(w, variable_node),
                 }
             }
-            return walkExpression(w, full.ast.assign_expr);
+            return walkExpression(w, full.ast.value_expr);
         },
 
         .bit_not,