workaround function declaration quirks in ES6+ (#5833)

fixes #1666

lib/compress.js

@@ -1375,6 +1375,11 @@ Compressor.prototype.compress = function(node) {
             var d = this.definition();
             if (!d.first_decl && d.references.length == 0) d.first_decl = this;
         });
+        def(AST_SymbolDefun, function() {
+            var d = this.definition();
+            if (!d.first_decl && d.references.length == 0) d.first_decl = this;
+            if (d.orig.length > 1 && d.scope.resolve() !== this.scope) d.fixed = false;
+        });
         def(AST_SymbolImport, function() {
             var d = this.definition();
             d.first_decl = this;
@@ -1893,6 +1898,7 @@ Compressor.prototype.compress = function(node) {
         if (stat instanceof AST_LambdaDefinition) {
             var def = stat.name.definition();
             var scope = stat.name.scope;
+            if (def.orig.length > 1 && def.scope.resolve() !== scope) return false;
             return def.scope === scope || all(def.references, function(ref) {
                 var s = ref.scope;
                 do {
@@ -2405,6 +2411,7 @@ Compressor.prototype.compress = function(node) {
                     }
                     var read_toplevel = false;
                     var modify_toplevel = false;
+                    var defun_scopes = get_defun_scopes(lhs);
                     // Locate symbols which may execute code outside of scanning range
                     var enclosed = new Dictionary();
                     var well_defined = true;
@@ -2535,8 +2542,11 @@ Compressor.prototype.compress = function(node) {
                 if (parent instanceof AST_For) {
                     if (node !== parent.init) return true;
                 }
-                if (node instanceof AST_Assign) {
+                if (node instanceof AST_Assign) return node.operator != "=" && lhs.equals(node.left);
-                    return node.operator != "=" && lhs.equals(node.left);
+                if (node instanceof AST_BlockStatement) {
+                    return defun_scopes && !all(defun_scopes, function(scope) {
+                        return node !== scope;
+                    });
                 }
                 if (node instanceof AST_Call) {
                     if (!(lhs instanceof AST_PropAccess)) return false;
@@ -3437,6 +3447,33 @@ Compressor.prototype.compress = function(node) {
                 }
             }
 
+            function get_defun_scopes(lhs) {
+                if (!(lhs instanceof AST_SymbolDeclaration
+                    || lhs instanceof AST_SymbolRef
+                    || lhs instanceof AST_Destructured)) return;
+                var scopes = [];
+                lhs.mark_symbol(function(node) {
+                    if (node instanceof AST_Symbol) {
+                        var def = node.definition();
+                        var scope = def.scope.resolve();
+                        var found = false;
+                        var avoid = def.orig.reduce(function(scopes, sym) {
+                            if (sym instanceof AST_SymbolDefun) {
+                                if (sym.scope !== scope) push_uniq(scopes, sym.scope);
+                            } else {
+                                found = true;
+                            }
+                            return scopes;
+                        }, []);
+                        if (found) avoid.forEach(function(scope) {
+                            push_uniq(scopes, scope);
+                        });
+                    }
+                });
+                if (scopes.length == 0) return;
+                return scopes;
+            }
+
             function is_lhs_local(lhs) {
                 var sym = root_expr(lhs);
                 if (!(sym instanceof AST_SymbolRef)) return false;

test/compress/blocks.js

@@ -47,3 +47,45 @@ keep_some_blocks: {
         } else stuff();
     }
 }
+
+issue_1666: {
+    input: {
+        var a = 42;
+        {
+            function a() {}
+            a();
+        }
+        console.log("PASS");
+    }
+    expect: {
+        var a = 42;
+        {
+            function a() {}
+            a();
+        }
+        console.log("PASS");
+    }
+    expect_stdout: true
+}
+
+issue_1666_strict: {
+    input: {
+        "use strict";
+        var a = 42;
+        {
+            function a() {}
+            a();
+        }
+        console.log("PASS");
+    }
+    expect: {
+        "use strict";
+        var a = 42;
+        {
+            function a() {}
+            a();
+        }
+        console.log("PASS");
+    }
+    expect_stdout: true
+}

test/compress/collapse_vars.js

@@ -10172,3 +10172,115 @@ issue_5779: {
     }
     expect_stdout: "PASS"
 }
+
+issue_1666: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var x = 42;
+        {
+            x();
+            function x() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof x);
+    }
+    expect: {
+        var x = 42;
+        {
+            x();
+            function x() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof x);
+    }
+    expect_stdout: true
+}
+
+issue_1666_strict: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        "use strict";
+        var x = 42;
+        {
+            x();
+            function x() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof x);
+    }
+    expect: {
+        "use strict";
+        var x = 42;
+        {
+            x();
+            function x() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof x);
+    }
+    expect_stdout: true
+}
+
+issue_1666_undefined: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var undefined = 42;
+        {
+            undefined();
+            function undefined() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof undefined);
+    }
+    expect: {
+        var undefined = 42;
+        {
+            undefined();
+            function undefined() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof undefined);
+    }
+    expect_stdout: true
+}
+
+issue_1666_undefined_strict: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        "use strict";
+        var undefined = 42;
+        {
+            undefined();
+            function undefined() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof undefined);
+    }
+    expect: {
+        "use strict";
+        var undefined = 42;
+        {
+            undefined();
+            function undefined() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof undefined);
+    }
+    expect_stdout: true
+}

test/compress/reduce_vars.js

@@ -8222,3 +8222,127 @@ issue_5777_2: {
     }
     expect_stdout: "PASS"
 }
+
+issue_1666: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var x = 42;
+        {
+            x();
+            function x() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof x);
+    }
+    expect: {
+        var x = 42;
+        {
+            x();
+            function x() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof x);
+    }
+    expect_stdout: true
+}
+
+issue_1666_strict: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        var x = 42;
+        {
+            x();
+            function x() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof x);
+    }
+    expect: {
+        "use strict";
+        var x = 42;
+        {
+            x();
+            function x() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof x);
+    }
+    expect_stdout: true
+}
+
+issue_1666_undefined: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var undefined = 42;
+        {
+            undefined();
+            function undefined() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof undefined);
+    }
+    expect: {
+        var undefined = 42;
+        {
+            undefined();
+            function undefined() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof undefined);
+    }
+    expect_stdout: true
+}
+
+issue_1666_undefined_strict: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        var undefined = 42;
+        {
+            undefined();
+            function undefined() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof undefined);
+    }
+    expect: {
+        "use strict";
+        var undefined = 42;
+        {
+            undefined();
+            function undefined() {
+                console.log("foo");
+            }
+        }
+        console.log(typeof undefined);
+    }
+    expect_stdout: true
+}