avoid double counting within single-use functions (#2785)

fixes #2783

lib/compress.js

@@ -5022,6 +5022,7 @@ merge(Compressor.prototype, {
             }
             if (single_use && fixed) {
                 if (fixed instanceof AST_Defun) {
+                    fixed._squeezed = true;
                     fixed = make_node(AST_Function, fixed, fixed);
                 }
                 var value;

test/compress/functions.js

@@ -1951,3 +1951,41 @@ issue_2737_2: {
     }
     expect_stdout: "PASS"
 }
+
+issue_2783: {
+    options = {
+        collapse_vars: true,
+        conditionals: true,
+        if_return: true,
+        inline: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function() {
+            return g;
+            function f(a) {
+                var b = a.b;
+                if (b) return b;
+                return a;
+            }
+            function g(o, i) {
+                while (i--) {
+                    console.log(f(o));
+                }
+            }
+        })()({ b: "PASS" }, 1);
+    }
+    expect: {
+        (function() {
+            return function(o,i) {
+                while (i--) console.log(f(o));
+            };
+            function f(a) {
+                var b = a.b;
+                return b || a;
+            }
+        })()({ b: "PASS" },1);
+    }
+    expect_stdout: "PASS"
+}