warn & drop `#__PURE__` iff IIFE is dropped (#1511)

- consolidate `side-effects` optimisations
- improve string `+` optimisation
- enhance literal & `conditionals` optimisations

7 files changed, 136 insertions, 25 deletions

diff --git a/test/compress/conditionals.js b/test/compress/conditionals.js
index d88c5b90..074d2a65 100644
--- a/test/compress/conditionals.js
+++ b/test/compress/conditionals.js
@@ -50,7 +50,8 @@ ifs_3_should_warn: {
         conditionals : true,
         dead_code    : true,
         evaluate     : true,
-        booleans     : true
+        booleans     : true,
+        side_effects : true,
     };
     input: {
         var x, y;
@@ -135,16 +136,28 @@ ifs_6: {
         comparisons: true
     };
     input: {
-        var x;
+        var x, y;
         if (!foo && !bar && !baz && !boo) {
             x = 10;
         } else {
             x = 20;
         }
+        if (y) {
+            x[foo] = 10;
+        } else {
+            x[foo] = 20;
+        }
+        if (foo) {
+            x[bar] = 10;
+        } else {
+            x[bar] = 20;
+        }
     }
     expect: {
-        var x;
+        var x, y;
         x = foo || bar || baz || boo ? 20 : 10;
+        x[foo] = y ? 10 : 20;
+        foo ? x[bar] = 10 : x[bar] = 20;
     }
 }
 
@@ -159,10 +172,16 @@ cond_1: {
         } else {
             do_something(y);
         }
+        if (some_condition()) {
+            side_effects(x);
+        } else {
+            side_effects(y);
+        }
     }
     expect: {
         var do_something;
         do_something(some_condition() ? x : y);
+        some_condition() ? side_effects(x) : side_effects(y);
     }
 }
 
@@ -213,10 +232,16 @@ cond_4: {
         } else {
             do_something();
         }
+        if (some_condition()) {
+            side_effects();
+        } else {
+            side_effects();
+        }
     }
     expect: {
         var do_something;
         some_condition(), do_something();
+        some_condition(), side_effects();
     }
 }
 
@@ -250,7 +275,8 @@ cond_5: {
 cond_7: {
     options = {
         conditionals: true,
-        evaluate    : true
+        evaluate    : true,
+        side_effects: true,
     };
     input: {
         var x, y, z, a, b;
@@ -714,6 +740,7 @@ issue_1154: {
         conditionals: true,
         evaluate    : true,
         booleans    : true,
+        side_effects: true,
     };
     input: {
         function f1(x) { return x ? -1 : -1; }
@@ -742,7 +769,7 @@ issue_1154: {
         function g2() { return g(), 2; }
         function g3() { return g(), -4; }
         function g4() { return g(), !1; }
-        function g5() { return g(), void 0; }
+        function g5() { return void g(); }
         function g6() { return g(), "number"; }
     }
 }
@@ -750,7 +777,8 @@ issue_1154: {
 no_evaluate: {
     options = {
         conditionals: true,
-        evaluate    : false
+        evaluate    : false,
+        side_effects: true,
     }
     input: {
         function f(b) {
diff --git a/test/compress/dead-code.js b/test/compress/dead-code.js
index 2596e80e..cd96d02d 100644
--- a/test/compress/dead-code.js
+++ b/test/compress/dead-code.js
@@ -64,7 +64,8 @@ dead_code_constant_boolean_should_warn_more: {
         loops        : true,
         booleans     : true,
         conditionals : true,
-        evaluate     : true
+        evaluate     : true,
+        side_effects : true,
     };
     input: {
         while (!((foo && bar) || (x + "0"))) {
diff --git a/test/compress/evaluate.js b/test/compress/evaluate.js
index 5cefadc8..6bed73fb 100644
--- a/test/compress/evaluate.js
+++ b/test/compress/evaluate.js
@@ -624,25 +624,35 @@ in_boolean_context: {
     options = {
         booleans: true,
         evaluate: true,
+        sequences: true,
+        side_effects: true,
     }
     input: {
-        !42;
-        !"foo";
-        ![1, 2];
-        !/foo/;
-        !b(42);
-        !b("foo");
-        !b([1, 2]);
-        !b(/foo/);
+        console.log(
+            !42,
+            !"foo",
+            ![1, 2],
+            !/foo/,
+            !b(42),
+            !b("foo"),
+            !b([1, 2]),
+            !b(/foo/),
+            ![1, foo()],
+            ![1, foo(), 2]
+        );
     }
     expect: {
-        !1;
-        !1;
-        !1;
-        !1;
-        !b(42);
-        !b("foo");
-        !b([1, 2]);
-        !b(/foo/);
+        console.log(
+            !1,
+            !1,
+            !1,
+            !1,
+            !b(42),
+            !b("foo"),
+            !b([1, 2]),
+            !b(/foo/),
+            ![1, foo()],
+            (foo(), !1)
+        );
     }
 }
diff --git a/test/compress/issue-1261.js b/test/compress/issue-1261.js
index dfbe2100..a872c578 100644
--- a/test/compress/issue-1261.js
+++ b/test/compress/issue-1261.js
@@ -116,3 +116,61 @@ pure_function_calls_toplevel: {
         "WARN: Dropping unused variable iife1 [test/compress/issue-1261.js:84,12]",
     ]
 }
+
+should_warn: {
+    options = {
+        booleans: true,
+        conditionals: true,
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        /* @__PURE__ */(function(){x})(), void/* @__PURE__ */(function(){y})();
+        /* @__PURE__ */(function(){x})() || true ? foo() : bar();
+        true || /* @__PURE__ */(function(){y})() ? foo() : bar();
+        /* @__PURE__ */(function(){x})() && false ? foo() : bar();
+        false && /* @__PURE__ */(function(){y})() ? foo() : bar();
+        /* @__PURE__ */(function(){x})() + "foo" ? bar() : baz();
+        "foo" + /* @__PURE__ */(function(){y})() ? bar() : baz();
+        /* @__PURE__ */(function(){x})() ? foo() : foo();
+        [/* @__PURE__ */(function(){x})()] ? foo() : bar();
+        !{ foo: /* @__PURE__ */(function(){x})() } ? bar() : baz();
+    }
+    expect: {
+        foo();
+        foo();
+        bar();
+        bar();
+        bar();
+        bar();
+        foo();
+        foo();
+        baz();
+    }
+    expect_warnings: [
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:128,61]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:128,23]",
+        "WARN: Dropping side-effect-free statement [test/compress/issue-1261.js:128,23]",
+        "WARN: Boolean || always true [test/compress/issue-1261.js:129,23]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:129,23]",
+        "WARN: Condition always true [test/compress/issue-1261.js:129,23]",
+        "WARN: Boolean || always true [test/compress/issue-1261.js:130,8]",
+        "WARN: Condition always true [test/compress/issue-1261.js:130,8]",
+        "WARN: Boolean && always false [test/compress/issue-1261.js:131,23]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:131,23]",
+        "WARN: Condition always false [test/compress/issue-1261.js:131,23]",
+        "WARN: Boolean && always false [test/compress/issue-1261.js:132,8]",
+        "WARN: Condition always false [test/compress/issue-1261.js:132,8]",
+        "WARN: + in boolean context always true [test/compress/issue-1261.js:133,23]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:133,23]",
+        "WARN: Condition always true [test/compress/issue-1261.js:133,23]",
+        "WARN: + in boolean context always true [test/compress/issue-1261.js:134,8]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:134,31]",
+        "WARN: Condition always true [test/compress/issue-1261.js:134,8]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:135,23]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:136,24]",
+        "WARN: Condition always true [test/compress/issue-1261.js:136,8]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:137,31]",
+        "WARN: Condition always false [test/compress/issue-1261.js:137,8]",
+    ]
+}
diff --git a/test/compress/issue-1275.js b/test/compress/issue-1275.js
index e88e284c..51f696af 100644
--- a/test/compress/issue-1275.js
+++ b/test/compress/issue-1275.js
@@ -35,7 +35,7 @@ string_plus_optimization: {
                 throw "nope";
             }
             try {
-                console.log('0' + throwing_function() ? "yes" : "no");
+                console.log((throwing_function(), "yes"));
             } catch (ex) {
                 console.log(ex);
             }
diff --git a/test/compress/typeof.js b/test/compress/typeof.js
index fb391573..7bf8e5e3 100644
--- a/test/compress/typeof.js
+++ b/test/compress/typeof.js
@@ -29,6 +29,7 @@ typeof_in_boolean_context: {
         booleans     : true,
         evaluate     : true,
         conditionals : true,
+        side_effects : true,
     };
     input: {
         function f1(x) { return typeof x ? "yes" : "no"; }
@@ -36,12 +37,14 @@ typeof_in_boolean_context: {
         typeof 0 ? foo() : bar();
         !typeof console.log(1);
         var a = !typeof console.log(2);
+        if (typeof (1 + foo()));
     }
     expect: {
         function f1(x) { return "yes"; }
         function f2() { return g(), "Yes"; }
         foo();
-        !(console.log(1), !0);
+        console.log(1);
         var a = !(console.log(2), !0);
+        foo();
     }
 }
diff --git a/test/mocha/minify.js b/test/mocha/minify.js
index 0cf8c5c1..baac2a41 100644
--- a/test/mocha/minify.js
+++ b/test/mocha/minify.js
@@ -154,6 +154,17 @@ describe("minify", function() {
             var code = result.code;
             assert.strictEqual(code, "//  comment1   comment2\nbar();");
         });
+        it("should not drop #__PURE__ hint if function is retained", function() {
+            var result = Uglify.minify("var a = /*#__PURE__*/(function(){return 1})();", {
+                fromString: true,
+                output: {
+                    comments: "all",
+                    beautify: false,
+                }
+            });
+            var code = result.code;
+            assert.strictEqual(code, "var a=/*#__PURE__*/function(){return 1}();");
+        })
     });
 
     describe("JS_Parse_Error", function() {