Evaluate some BigInt operations (#1390)

* Evaluate some BigInt operations. Closes #1388

* Prevent division by zero

lib/compress/common.js

@@ -44,6 +44,7 @@
 import {
     AST_Array,
     AST_Arrow,
+    AST_BigInt,
     AST_BlockStatement,
     AST_Call,
     AST_Chain,
@@ -124,6 +125,8 @@ export function make_node_from_constant(val, orig) {
             operator: "-",
             expression: make_node(AST_Infinity, orig)
         }) : make_node(AST_Infinity, orig);
+      case "bigint":
+        return make_node(AST_BigInt, orig, { value: val.toString() });
       case "boolean":
         return make_node(val ? AST_True : AST_False, orig);
       case "undefined":

lib/compress/evaluate.js

@@ -133,7 +133,14 @@ def_eval(AST_Constant, function () {
     return this.getValue();
 });
 
-def_eval(AST_BigInt, return_this);
+const supports_bigint = typeof BigInt === "function";
+def_eval(AST_BigInt, function () {
+    if (supports_bigint) {
+        return BigInt(this.value);
+    } else {
+        return this;
+    }
+});
 
 def_eval(AST_RegExp, function (compressor) {
     let evaluated = compressor.evaluated_regexps.get(this.value);
@@ -257,7 +264,6 @@ def_eval(AST_Binary, function (compressor, depth) {
     var right = this.right._eval(compressor, depth);
     if (right === this.right)
         return this;
-    var result;
 
     if (left != null
         && right != null
@@ -269,6 +275,17 @@ def_eval(AST_Binary, function (compressor, depth) {
         return this;
     }
 
+    // Do not mix BigInt and Number; Don't use `>>>` on BigInt or `/ 0n`
+    if (
+        (typeof left === "bigint") !== (typeof right === "bigint")
+        || typeof left === "bigint"
+            && (this.operator === ">>>"
+                || this.operator === "/" && Number(right) === 0)
+    ) {
+        return this;
+    }
+
+    var result;
     switch (this.operator) {
         case "&&": result = left && right; break;
         case "||": result = left || right; break;
@@ -278,7 +295,7 @@ def_eval(AST_Binary, function (compressor, depth) {
         case "^": result = left ^ right; break;
         case "+": result = left + right; break;
         case "*": result = left * right; break;
-        case "**": result = Math.pow(left, right); break;
+        case "**": result = left ** right; break;
         case "/": result = left / right; break;
         case "%": result = left % right; break;
         case "-": result = left - right; break;
@@ -296,7 +313,7 @@ def_eval(AST_Binary, function (compressor, depth) {
         default:
             return this;
     }
-    if (isNaN(result) && compressor.find_parent(AST_With)) {
+    if (typeof result === "number" && isNaN(result) && compressor.find_parent(AST_With)) {
         // leave original expression as is
         return this;
     }

test/compress/big_int.js

@@ -62,12 +62,30 @@ big_int_math: {
         defaults: true
     }
     input: {
-        const sum = 10n + 15n;
-        const exp = 5n ** 10n;
-        const sub = 1n - 3n;
-        const mul = 5n * 5n;
-        const div = 15n / 5n;
-        const regular_number = 1 * 10;
+        console.log({
+            sum: 10n + 15n,
+            exp: 2n ** 3n,
+            sub: 1n - 3n,
+            mul: 5n * 5n,
+            div: 15n / 5n,
+        });
     }
-    expect_exact: "const sum=10n+15n,exp=5n**10n,sub=1n-3n,mul=5n*5n,div=15n/5n,regular_number=10;"
+    expect_exact: "console.log({sum:25n,exp:8n,sub:-2n,mul:25n,div:3n});"
+    expect_stdout: true
+}
+
+big_int_math_counter_examples: {
+    node_version = ">= 12"
+    options = {
+        defaults: true
+    }
+    input: {
+        console.log({
+            mixing_types: 1 * 10n,
+            bad_shift: 1n >>> 0n,
+            bad_div: 1n / 0n,
+        });
+    }
+    expect_exact: "console.log({mixing_types:1*10n,bad_shift:1n>>>0n,bad_div:1n/0n});"
+    expect_stdout: true
 }