enhance `inline` (#3832)

1 files changed, 34 insertions, 2 deletions

diff --git a/lib/compress.js b/lib/compress.js
index c679a8b2..15db2332 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -225,7 +225,7 @@ merge(Compressor.prototype, {
         // output and performance.
         descend(node, this);
         var opt = node.optimize(this);
-        if (is_scope) {
+        if (is_scope && opt === node) {
             opt.drop_unused(this);
             descend(opt, this);
         }
@@ -3981,6 +3981,38 @@ merge(Compressor.prototype, {
         return self;
     });
 
+    OPT(AST_Function, function(self, compressor) {
+        self.body = tighten_body(self.body, compressor);
+        if (compressor.option("inline")) for (var i = 0; i < self.body.length; i++) {
+            var stat = self.body[i];
+            if (stat instanceof AST_Directive) continue;
+            if (stat instanceof AST_Return) {
+                var call = stat.value;
+                if (!call || call.TYPE != "Call") break;
+                var fn = call.expression;
+                if (fn instanceof AST_SymbolRef) {
+                    fn = fn.fixed_value();
+                }
+                if (!(fn instanceof AST_Lambda)) break;
+                if (fn.uses_arguments) break;
+                if (fn.contains_this()) break;
+                var j = fn.argnames.length;
+                if (j > 0 && compressor.option("inline") < 2) break;
+                if (j > self.argnames.length) break;
+                if (j < self.argnames.length && !compressor.drop_fargs(fn, call)) break;
+                while (--j >= 0) {
+                    var arg = call.args[j];
+                    if (!(arg instanceof AST_SymbolRef)) break;
+                    if (arg.definition() !== self.argnames[j].definition()) break;
+                }
+                if (j >= 0) break;
+                return call.expression;
+            }
+            break;
+        }
+        return self;
+    });
+
     AST_Scope.DEFMETHOD("drop_unused", function(compressor) {
         if (!compressor.option("unused")) return;
         if (compressor.has_directive("use asm")) return;
@@ -6133,7 +6165,7 @@ merge(Compressor.prototype, {
 
         function can_substitute_directly() {
             if (var_assigned) return;
-            if (compressor.option("inline") <= 1 && fn.argnames.length) return;
+            if (compressor.option("inline") < 2 && fn.argnames.length) return;
             if (!fn.variables.all(function(def) {
                 return def.references.length < 2 && def.orig[0] instanceof AST_SymbolFunarg;
             })) return;