fix corner cases in inline & unused (#5534)

fixes #5533

Author: alexlamsl

lib/compress.js

@@ -6948,7 +6948,7 @@ Compressor.prototype.compress = function(node) {
                 node.properties = properties;
                 return node;
             }
-            if (node instanceof AST_SymbolDeclaration) return node.definition().id in in_use_ids ? node : null;
+            if (node instanceof AST_SymbolDeclaration) return trim_decl(node);
         });
         var tt = new TreeTransformer(function(node, descend, in_list) {
             var parent = tt.parent();
@@ -7063,9 +7063,7 @@ Compressor.prototype.compress = function(node) {
                         } else {
                             var trimmed = trim_destructured(rest, make_node(AST_Array, parent, {
                                 elements: args.slice(argnames.length),
-                            }), function(node) {
-                                return node.definition().id in in_use_ids ? node : null;
-                            }, !node.uses_arguments, rest);
+                            }), trim_decl, !node.uses_arguments, rest);
                             rest = trimmed.name;
                             args.length = argnames.length;
                             if (trimmed.value.elements.length) [].push.apply(args, trimmed.value.elements);
@@ -7095,6 +7093,8 @@ Compressor.prototype.compress = function(node) {
                             } else if (trim) {
                                 log(sym, "Dropping unused function argument {name}");
                                 argnames.pop();
+                                def.eliminated++;
+                                sym.unused = true;
                             } else {
                                 sym.unused = true;
                             }
@@ -7104,9 +7104,7 @@ Compressor.prototype.compress = function(node) {
                             if (!args || spread < i) {
                                 funarg = sym.transform(trimmer);
                             } else {
-                                var trimmed = trim_destructured(sym, args[i], function(node) {
-                                    return node.definition().id in in_use_ids ? node : null;
-                                }, trim_value, sym);
+                                var trimmed = trim_destructured(sym, args[i], trim_decl, trim_value, sym);
                                 funarg = trimmed.name;
                                 if (trimmed.value) args[i] = trimmed.value;
                             }
@@ -7706,6 +7704,12 @@ Compressor.prototype.compress = function(node) {
             return (node instanceof AST_DefaultValue ? node.name : node) instanceof AST_SymbolDeclaration;
         }
 
+        function trim_decl(node) {
+            if (node.definition().id in in_use_ids) return node;
+            if (node instanceof AST_SymbolFunarg) node.unused = true;
+            return null;
+        }
+
         function trim_default(trimmer, node) {
             node.value = node.value.transform(tt);
             var name = node.name.transform(trimmer);
@@ -13660,7 +13664,7 @@ Compressor.prototype.compress = function(node) {
                 if (def.orig.length == 1 && fn.functions.has(name)) return;
                 if (!all(def.orig, function(sym) {
                     if (sym instanceof AST_SymbolConst) return false;
-                    if (sym instanceof AST_SymbolFunarg) return def.scope.resolve() !== fn;
+                    if (sym instanceof AST_SymbolFunarg) return !sym.unused && def.scope.resolve() !== fn;
                     if (sym instanceof AST_SymbolLet) return false;
                     return true;
                 })) return;