fix corner case in evaluate (#3344)

lib/compress.js

@@ -537,13 +537,11 @@ merge(Compressor.prototype, {
             var d = sym.definition();
             var safe = safe_to_assign(tw, d, sym.scope, node.right);
             d.assignments++;
-            if (!safe) return;
             var fixed = d.fixed;
             if (!fixed && node.operator != "=") return;
             var eq = node.operator == "=";
             var value = eq ? node.right : node;
             if (is_modified(compressor, tw, node, value, 0)) return;
-            d.references.push(sym);
             if (!eq) d.chained = true;
             d.fixed = eq ? function() {
                 return node.right;
@@ -554,6 +552,8 @@ merge(Compressor.prototype, {
                     right: node.right
                 });
             };
+            if (!safe) return;
+            d.references.push(sym);
             mark(tw, d, false);
             node.right.walk(tw);
             mark(tw, d, true);
@@ -783,10 +783,8 @@ merge(Compressor.prototype, {
             var d = exp.definition();
             var safe = safe_to_assign(tw, d, exp.scope, true);
             d.assignments++;
-            if (!safe) return;
             var fixed = d.fixed;
             if (!fixed) return;
-            d.references.push(exp);
             d.chained = true;
             d.fixed = function() {
                 return make_node(AST_Binary, node, {
@@ -800,6 +798,8 @@ merge(Compressor.prototype, {
                     })
                 });
             };
+            if (!safe) return;
+            d.references.push(exp);
             mark(tw, d, true);
             return true;
         });

test/compress/evaluate.js

@@ -1610,3 +1610,47 @@ truthy_loops: {
         }
     }
 }
+
+if_increment: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a) {
+            if (console)
+                return ++a;
+        }(0));
+    }
+    expect: {
+        console.log(function(a) {
+            if (console)
+                return 1;
+        }());
+    }
+    expect_stdout: "1"
+}
+
+try_increment: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a) {
+            try {
+                return ++a;
+            } catch (e) {}
+        }(0));
+    }
+    expect: {
+        console.log(function(a) {
+            try {
+                return 1;
+            } catch (e) {}
+        }());
+    }
+    expect_stdout: "1"
+}