fix `has_side_effects()` (#1675)

`AST_Try` is an `AST_Block`, so besides try block we also need to inspect catch and finally blocks for possible side effects.

Also extend this functionality to handle `AST_If` and `AST_LabeledStatement` while we are at it.

fixes #1673

2 files changed, 149 insertions, 13 deletions

diff --git a/lib/compress.js b/lib/compress.js
index bea9c9a4..805a84a7 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1600,14 +1600,29 @@ merge(Compressor.prototype, {
             return false;
         });
 
-        def(AST_Block, function(compressor){
-            for (var i = this.body.length; --i >= 0;) {
-                if (this.body[i].has_side_effects(compressor))
+        function any(list, compressor) {
+            for (var i = list.length; --i >= 0;)
+                if (list[i].has_side_effects(compressor))
                     return true;
-            }
             return false;
-        });
+        }
 
+        def(AST_Block, function(compressor){
+            return any(this.body, compressor);
+        });
+        def(AST_Try, function(compressor){
+            return any(this.body, compressor)
+                || this.bcatch && this.bcatch.has_side_effects(compressor)
+                || this.bfinally && this.bfinally.has_side_effects(compressor);
+        });
+        def(AST_If, function(compressor){
+            return this.condition.has_side_effects(compressor)
+                || this.body && this.body.has_side_effects(compressor)
+                || this.alternative && this.alternative.has_side_effects(compressor);
+        });
+        def(AST_LabeledStatement, function(compressor){
+            return this.body.has_side_effects(compressor);
+        });
         def(AST_SimpleStatement, function(compressor){
             return this.body.has_side_effects(compressor);
         });
@@ -1633,19 +1648,13 @@ merge(Compressor.prototype, {
             return this.global() && this.undeclared();
         });
         def(AST_Object, function(compressor){
-            for (var i = this.properties.length; --i >= 0;)
-                if (this.properties[i].has_side_effects(compressor))
-                    return true;
-            return false;
+            return any(this.properties, compressor);
         });
         def(AST_ObjectProperty, function(compressor){
             return this.value.has_side_effects(compressor);
         });
         def(AST_Array, function(compressor){
-            for (var i = this.elements.length; --i >= 0;)
-                if (this.elements[i].has_side_effects(compressor))
-                    return true;
-            return false;
+            return any(this.elements, compressor);
         });
         def(AST_Dot, function(compressor){
             if (!compressor.option("pure_getters")) return true;
diff --git a/test/compress/issue-1673.js b/test/compress/issue-1673.js
new file mode 100644
index 00000000..59686abf
--- /dev/null
+++ b/test/compress/issue-1673.js
@@ -0,0 +1,127 @@
+side_effects_catch: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            function g() {
+                try {
+                    throw 0;
+                } catch (e) {
+                    console.log("PASS");
+                }
+            }
+            g();
+        }
+        f();
+    }
+    expect: {
+        function f() {
+            (function() {
+                try {
+                    throw 0;
+                } catch (e) {
+                    console.log("PASS");
+                }
+            })();
+        }
+        f();
+    }
+    expect_stdout: "PASS"
+}
+
+side_effects_else: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function f(x) {
+            function g() {
+                if (x);
+                else console.log("PASS");
+            }
+            g();
+        }
+        f(0);
+    }
+    expect: {
+        function f(x) {
+            (function() {
+                if (x);
+                else console.log("PASS");
+            })();
+        }
+        f(0);
+    }
+    expect_stdout: "PASS"
+}
+
+side_effects_finally: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            function g() {
+                try {
+                } catch (e) {
+                } finally {
+                    console.log("PASS");
+                }
+            }
+            g();
+        }
+        f();
+    }
+    expect: {
+        function f() {
+            (function() {
+                try {
+                } catch (e) {
+                } finally {
+                    console.log("PASS");
+                }
+            })();
+        }
+        f();
+    }
+    expect_stdout: "PASS"
+}
+
+side_effects_label: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function f(x) {
+            function g() {
+                L: {
+                    console.log("PASS");
+                    break L;
+                }
+            }
+            g();
+        }
+        f(0);
+    }
+    expect: {
+        function f(x) {
+            (function() {
+                L: {
+                    console.log("PASS");
+                    break L;
+                }
+            })();
+        }
+        f(0);
+    }
+    expect_stdout: "PASS"
+}