implement function inlining (#2053)

- empty body
- single `AST_Return`
- single `AST_SimpleStatement`
- avoid `/*#__PURE__*/`

Miscellaneous
- enhance single-use function substitution

fixes #281

7 files changed, 458 insertions, 5 deletions

diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index 90d7ac93..158d1b4a 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -1146,7 +1146,7 @@ collapse_vars_constants: {
         function f3(x) {
             var b = x.prop;
             sideeffect1();
-            return b + -9;
+            return b + (function() { return -9; })();
         }
     }
 }
diff --git a/test/compress/evaluate.js b/test/compress/evaluate.js
index 99245d0d..27d08d47 100644
--- a/test/compress/evaluate.js
+++ b/test/compress/evaluate.js
@@ -644,6 +644,7 @@ unsafe_prototype_function: {
 call_args: {
     options = {
         evaluate: true,
+        inline: true,
         reduce_vars: true,
         toplevel: true,
     }
@@ -665,6 +666,7 @@ call_args: {
 call_args_drop_param: {
     options = {
         evaluate: true,
+        inline: true,
         keep_fargs: false,
         reduce_vars: true,
         toplevel: true,
diff --git a/test/compress/functions.js b/test/compress/functions.js
index a9ca23f8..180bb11a 100644
--- a/test/compress/functions.js
+++ b/test/compress/functions.js
@@ -21,6 +21,7 @@ iifes_returning_constants_keep_fargs_true: {
         join_vars     : true,
         reduce_vars   : true,
         cascade       : true,
+        inline        : true,
     }
     input: {
         (function(){ return -1.23; }());
@@ -56,6 +57,7 @@ iifes_returning_constants_keep_fargs_false: {
         join_vars     : true,
         reduce_vars   : true,
         cascade       : true,
+        inline        : true,
     }
     input: {
         (function(){ return -1.23; }());
@@ -82,6 +84,7 @@ issue_485_crashing_1530: {
         conditionals: true,
         dead_code: true,
         evaluate: true,
+        inline: true,
     }
     input: {
         (function(a) {
@@ -154,6 +157,7 @@ function_returning_constant_literal: {
         evaluate: true,
         cascade: true,
         unused: true,
+        inline: true,
     }
     input: {
         function greeter() {
diff --git a/test/compress/issue-1787.js b/test/compress/issue-1787.js
index 02fa0f91..2b5372be 100644
--- a/test/compress/issue-1787.js
+++ b/test/compress/issue-1787.js
@@ -1,6 +1,7 @@
 unary_prefix: {
     options = {
         evaluate: true,
+        inline: true,
         reduce_vars: true,
         unused: true,
     }
diff --git a/test/compress/issue-281.js b/test/compress/issue-281.js
new file mode 100644
index 00000000..6b1b4b40
--- /dev/null
+++ b/test/compress/issue-281.js
@@ -0,0 +1,433 @@
+collapse_vars_constants: {
+    options = {
+        collapse_vars: true,
+        evaluate: true,
+        inline: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        function f1(x) {
+            var a = 4, b = x.prop, c = 5, d = sideeffect1(), e = sideeffect2();
+            return b + (function() { return d - a * e - c; })();
+        }
+        function f2(x) {
+            var a = 4, b = x.prop, c = 5, not_used = sideeffect1(), e = sideeffect2();
+            return b + (function() { return -a * e - c; })();
+        }
+    }
+    expect: {
+        function f1(x) {
+            var b = x.prop, d = sideeffect1(), e = sideeffect2();
+            return b + (d - 4 * e - 5);
+        }
+        function f2(x) {
+            var b = x.prop;
+            sideeffect1();
+            return b + (-4 * sideeffect2() - 5);
+        }
+    }
+}
+
+modified: {
+    options = {
+        collapse_vars: true,
+        inline: true,
+        unused: true,
+    }
+    input: {
+        function f5(b) {
+            var a = function() {
+                return b;
+            }();
+            return b++ + a;
+        }
+        console.log(f5(1));
+    }
+    expect: {
+        function f5(b) {
+            var a = b;
+            return b++ + a;
+        }
+        console.log(f5(1));
+    }
+    expect_stdout: "2"
+}
+
+ref_scope: {
+    options = {
+        collapse_vars: true,
+        inline: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            var a = 1, b = 2, c = 3;
+            var a = c++, b = b /= a;
+            return function() {
+                return a;
+            }() + b;
+        }());
+    }
+    expect: {
+        console.log(function() {
+            var a = 1, b = 2, c = 3;
+            b = b /= a = c++;
+            return a + b;
+        }());
+    }
+    expect_stdout: true
+}
+
+safe_undefined: {
+    options = {
+        conditionals: true,
+        if_return: true,
+        inline: true,
+        unsafe: false,
+        unused: true,
+    }
+    mangle = {}
+    input: {
+        var a, c;
+        console.log(function(undefined) {
+            return function() {
+                if (a)
+                    return b;
+                if (c)
+                    return d;
+            };
+        }(1)());
+    }
+    expect: {
+        var a, c;
+        console.log(a ? b : c ? d : void 0);
+    }
+    expect_stdout: true
+}
+
+negate_iife_3: {
+    options = {
+        conditionals: true,
+        expression: true,
+        inline: true,
+        negate_iife: true,
+    }
+    input: {
+        (function(){ return t })() ? console.log(true) : console.log(false);
+    }
+    expect: {
+        t ? console.log(true) : console.log(false);
+    }
+}
+
+negate_iife_3_off: {
+    options = {
+        conditionals: true,
+        expression: true,
+        inline: true,
+        negate_iife: false,
+    }
+    input: {
+        (function(){ return t })() ? console.log(true) : console.log(false);
+    }
+    expect: {
+        t ? console.log(true) : console.log(false);
+    }
+}
+
+negate_iife_4: {
+    options = {
+        conditionals: true,
+        expression: true,
+        inline: true,
+        negate_iife: true,
+        sequences: true,
+    }
+    input: {
+        (function(){ return t })() ? console.log(true) : console.log(false);
+        (function(){
+            console.log("something");
+        })();
+    }
+    expect: {
+        t ? console.log(true) : console.log(false), console.log("something"), void 0;
+    }
+}
+
+negate_iife_5: {
+    options = {
+        conditionals: true,
+        expression: true,
+        inline: true,
+        negate_iife: true,
+        sequences: true,
+    }
+    input: {
+        if ((function(){ return t })()) {
+            foo(true);
+        } else {
+            bar(false);
+        }
+        (function(){
+            console.log("something");
+        })();
+    }
+    expect: {
+        t ? foo(true) : bar(false), console.log("something"), void 0;
+    }
+}
+
+negate_iife_5_off: {
+    options = {
+        conditionals: true,
+        expression: true,
+        inline: true,
+        negate_iife: false,
+        sequences: true,
+    };
+    input: {
+        if ((function(){ return t })()) {
+            foo(true);
+        } else {
+            bar(false);
+        }
+        (function(){
+            console.log("something");
+        })();
+    }
+    expect: {
+        t ? foo(true) : bar(false), console.log("something"), void 0;
+    }
+}
+
+issue_1254_negate_iife_true: {
+    options = {
+        expression: true,
+        inline: true,
+        negate_iife: true,
+    }
+    input: {
+        (function() {
+            return function() {
+                console.log('test')
+            };
+        })()();
+    }
+    expect_exact: 'console.log("test"),void 0;'
+    expect_stdout: true
+}
+
+issue_1254_negate_iife_nested: {
+    options = {
+        expression: true,
+        inline: true,
+        negate_iife: true,
+    }
+    input: {
+        (function() {
+            return function() {
+                console.log('test')
+            };
+        })()()()()();
+    }
+    expect_exact: '(console.log("test"),void 0)()()();'
+}
+
+negate_iife_issue_1073: {
+    options = {
+        conditionals: true,
+        evaluate: true,
+        inline: true,
+        negate_iife: true,
+        reduce_vars: true,
+        sequences: true,
+        unused: true,
+    };
+    input: {
+        new (function(a) {
+            return function Foo() {
+                this.x = a;
+                console.log(this);
+            };
+        }(7))();
+    }
+    expect: {
+        new function() {
+            this.x = 7,
+            console.log(this);
+        }();
+    }
+    expect_stdout: true
+}
+
+issue_1288_side_effects: {
+    options = {
+        conditionals: true,
+        evaluate: true,
+        inline: true,
+        negate_iife: true,
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    };
+    input: {
+        if (w) ;
+        else {
+            (function f() {})();
+        }
+        if (!x) {
+            (function() {
+                x = {};
+            })();
+        }
+        if (y)
+            (function() {})();
+        else
+            (function(z) {
+                return z;
+            })(0);
+    }
+    expect: {
+        w;
+        x || (x = {});
+        y;
+    }
+}
+
+inner_var_for_in_1: {
+    options = {
+        evaluate: true,
+        inline: true,
+        reduce_vars: true,
+    }
+    input: {
+        function f() {
+            var a = 1, b = 2;
+            for (b in (function() {
+                return x(a, b, c);
+            })()) {
+                var c = 3, d = 4;
+                x(a, b, c, d);
+            }
+            x(a, b, c, d);
+        }
+    }
+    expect: {
+        function f() {
+            var a = 1, b = 2;
+            for (b in x(1, b, c)) {
+                var c = 3, d = 4;
+                x(1, b, c, d);
+            }
+            x(1, b, c, d);
+        }
+    }
+}
+
+issue_1595_3: {
+    options = {
+        evaluate: true,
+        inline: true,
+        passes: 2,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function f(a) {
+            return g(a + 1);
+        })(2);
+    }
+    expect: {
+        g(3);
+    }
+}
+
+issue_1758: {
+    options = {
+        inline: true,
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(function(c) {
+            var undefined = 42;
+            return function() {
+                c--;
+                c--, c.toString();
+                return;
+            }();
+        }());
+    }
+    expect: {
+        console.log(function(c) {
+            var undefined = 42;
+            return c--, c--, void c.toString();
+        }());
+    }
+    expect_stdout: "undefined"
+}
+wrap_iife: {
+    options = {
+        inline: true,
+        negate_iife: false,
+    }
+    beautify = {
+        wrap_iife: true,
+    }
+    input: {
+        (function() {
+            return function() {
+                console.log('test')
+            };
+        })()();
+    }
+    expect_exact: 'console.log("test"),void 0;'
+}
+
+wrap_iife_in_expression: {
+    options = {
+        inline: true,
+        negate_iife: false,
+    }
+    beautify = {
+        wrap_iife: true,
+    }
+    input: {
+        foo = (function () {
+            return bar();
+        })();
+    }
+    expect_exact: 'foo=bar();'
+}
+
+wrap_iife_in_return_call: {
+    options = {
+        inline: true,
+        negate_iife: false,
+    }
+    beautify = {
+        wrap_iife: true,
+    }
+    input: {
+        (function() {
+            return (function() {
+                console.log('test')
+            })();
+        })()();
+    }
+    expect_exact: '(console.log("test"),void 0)();'
+}
+
+pure_annotation: {
+    options = {
+        inline: true,
+        side_effects: true,
+    }
+    input: {
+        /*@__PURE__*/(function() {
+            console.log("hello");
+        }());
+    }
+    expect_exact: ""
+}
diff --git a/test/compress/negate-iife.js b/test/compress/negate-iife.js
index 514a15c7..66d24270 100644
--- a/test/compress/negate-iife.js
+++ b/test/compress/negate-iife.js
@@ -22,7 +22,8 @@ negate_iife_1_off: {
 
 negate_iife_2: {
     options = {
-        negate_iife: true
+        inline: true,
+        negate_iife: true,
     };
     input: {
         (function(){ return {} })().x = 10;
@@ -32,6 +33,7 @@ negate_iife_2: {
 
 negate_iife_2_side_effects: {
     options = {
+        inline: true,
         negate_iife: true,
         side_effects: true,
     }
@@ -58,6 +60,7 @@ negate_iife_3_evaluate: {
     options = {
         conditionals: true,
         evaluate: true,
+        inline: true,
         negate_iife: true,
     }
     input: {
@@ -100,6 +103,7 @@ negate_iife_3_off_evaluate: {
     options = {
         conditionals: true,
         evaluate: true,
+        inline: true,
         negate_iife: false,
     }
     input: {
diff --git a/test/compress/reduce_vars.js b/test/compress/reduce_vars.js
index 078de82d..cef29832 100644
--- a/test/compress/reduce_vars.js
+++ b/test/compress/reduce_vars.js
@@ -2,6 +2,7 @@ reduce_vars: {
     options = {
         conditionals  : true,
         evaluate      : true,
+        inline        : true,
         global_defs   : {
             C : 0
         },
@@ -1032,6 +1033,7 @@ defun_inline_2: {
 defun_inline_3: {
     options = {
         evaluate: true,
+        inline: true,
         passes: 2,
         reduce_vars: true,
         side_effects: true,
@@ -1054,6 +1056,7 @@ defun_inline_3: {
 
 defun_call: {
     options = {
+        inline: true,
         reduce_vars: true,
         unused: true,
     }
@@ -1080,6 +1083,7 @@ defun_call: {
 
 defun_redefine: {
     options = {
+        inline: true,
         reduce_vars: true,
         unused: true,
     }
@@ -1112,6 +1116,7 @@ defun_redefine: {
 
 func_inline: {
     options = {
+        inline: true,
         reduce_vars: true,
         unused: true,
     }
@@ -1138,6 +1143,7 @@ func_inline: {
 
 func_modified: {
     options = {
+        inline: true,
         reduce_vars: true,
         unused: true,
     }
@@ -1340,10 +1346,9 @@ iife_func_side_effects: {
             console.log("z");
         }
         (function(a, b, c) {
-            function y() {
+            return function() {
                 console.log("FAIL");
-            }
-            return y + b();
+            } + b();
         })(x(), function() {
             return y();
         }, z());
@@ -1716,6 +1721,7 @@ redefine_arguments_1: {
 redefine_arguments_2: {
     options = {
         evaluate: true,
+        inline: true,
         keep_fargs: false,
         reduce_vars: true,
         side_effects: true,
@@ -1752,6 +1758,7 @@ redefine_arguments_2: {
 redefine_arguments_3: {
     options = {
         evaluate: true,
+        inline: true,
         keep_fargs: false,
         passes: 3,
         reduce_vars: true,
@@ -1828,6 +1835,7 @@ redefine_farg_1: {
 redefine_farg_2: {
     options = {
         evaluate: true,
+        inline: true,
         keep_fargs: false,
         reduce_vars: true,
         side_effects: true,
@@ -1864,6 +1872,7 @@ redefine_farg_2: {
 redefine_farg_3: {
     options = {
         evaluate: true,
+        inline: true,
         keep_fargs: false,
         passes: 3,
         reduce_vars: true,