From 97a79a6924215d0b9b7e2f79e23ae24a6e51f80e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?F=C3=A1bio=20Santos?= <fabiosantosart@gmail.com>
Date: Mon, 15 May 2023 17:41:03 +0100
Subject: [PATCH] Evaluate some BigInt operations. Closes #1388

---
 lib/compress/common.js   |  3 +++
 lib/compress/evaluate.js | 20 ++++++++++++++++++--
 test/compress/big_int.js |  2 +-
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/lib/compress/common.js b/lib/compress/common.js
index 8263522c8..2350c1ea8 100644
--- a/lib/compress/common.js
+++ b/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":
diff --git a/lib/compress/evaluate.js b/lib/compress/evaluate.js
index d249ee355..3add88758 100644
--- a/lib/compress/evaluate.js
+++ b/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);
@@ -246,6 +253,7 @@ const identity_comparison = makePredicate("== != === !==");
 const has_identity = value => typeof value === "object"
     || typeof value === "function"
     || typeof value === "symbol";
+const no_bigint_ops = new Set(['**', ">>>"]);
 
 def_eval(AST_Binary, function (compressor, depth) {
     if (!non_converting_binary.has(this.operator))
@@ -269,6 +277,14 @@ def_eval(AST_Binary, function (compressor, depth) {
         return this;
     }
 
+    // Do not mix BigInt and Number; Don't use Math.pow() on BigInt
+    if (
+        (typeof left === "bigint") !== (typeof right === "bigint")
+        || typeof left === "bigint" && no_bigint_ops.has(this.operator)
+    ) {
+        return this;
+    }
+
     switch (this.operator) {
         case "&&": result = left && right; break;
         case "||": result = left || right; break;
@@ -296,7 +312,7 @@ 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;
     }
diff --git a/test/compress/big_int.js b/test/compress/big_int.js
index 2f3501c04..cf28dceb5 100644
--- a/test/compress/big_int.js
+++ b/test/compress/big_int.js
@@ -70,5 +70,5 @@ big_int_math: {
         const div = 15n / 5n;
         const regular_number = 1 * 10;
     }
-    expect_exact: "const sum=10n+15n,exp=5n**10n,sub=1n-3n,mul=5n*5n,div=15n/5n,regular_number=10;"
+    expect_exact: "const sum=25n,exp=5n**10n,sub=-2n,mul=25n,div=3n,regular_number=10;"
 }