Added error for numeric literals larger than 2^53 - 1 #33202

JoshuaKGoldberg · 2019-09-03T03:13:44Z

Is there a better check for a numeric literal being too large than Number(text) >= Math.pow(2, 53) - 1? This performance difference should be negligible given that only literals of length 16 or more will go through Number.

IllusionMH · 2019-09-03T09:55:17Z

Better way would be using Number.isSafeInteger(), but it is not available in IE11 😭 (funny that this code uses unsafe integer Math.pow(2, 53) itself, but haven't seen cases when this won't work as expected).

Also looks like there are no tests for error messages related to "negative numbers". Are they needed here?

AnyhowStep · 2019-09-03T16:10:00Z

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MIN_SAFE_INTEGER

IllusionMH · 2019-09-03T16:10:12Z

@AnyhowStep as I said - not available in IE11 (both Number.isSafeInteger() and related constants)

UPD. Edited this message to propose inline constant, but AnyhowStep clarified this approach first.

AnyhowStep · 2019-09-03T16:13:17Z

Just copy-paste those constants into the TS source code. It's one or two lines at most and gets rid of the "unsafe" pow(2, 53)

Not a big deal

DanielRosenwasser · 2019-09-03T18:36:29Z

@typescript-bot test this
@typescript-bot user test this
@typescript-bot pack this

typescript-bot · 2019-09-03T18:36:37Z

Heya @DanielRosenwasser, I've started to run the parallelized community code test suite on this PR at 281e7a4. You can monitor the build here. It should now contribute to this PR's status checks.

typescript-bot · 2019-09-03T18:36:37Z

Heya @DanielRosenwasser, I've started to run the extended test suite on this PR at 281e7a4. You can monitor the build here. It should now contribute to this PR's status checks.

typescript-bot · 2019-09-03T18:36:38Z

Heya @DanielRosenwasser, I've started to run the tarball bundle task on this PR at 281e7a4. You can monitor the build here. It should now contribute to this PR's status checks.

DanielRosenwasser · 2019-09-03T18:42:42Z

src/compiler/checker.ts

+            if (diagnosticMessage) {
+                const withMinus = isPrefixUnaryExpression(node.parent) && node.parent.operator === SyntaxKind.MinusToken;
+                const literal = (withMinus ? "-" : "") + "0o" + node.text;
+                return grammarErrorOnNode(withMinus ? node.parent : node, diagnosticMessage, literal);


This is feeding in a userless literal parameter`. It's not a problem per se, but it is very weird to do.

DanielRosenwasser · 2019-09-03T18:45:51Z

src/compiler/checker.ts

+            // We can quickly bail out in two common cases:
+            // * Literals with 15 or fewer characters, as they aren't long enough to reach 2^53 - 1
+            // * Fractional numbers (e.g. 9000000000000000000000000000.000000001) are inherently imprecise anyway
+            if (text.length <= 15 || text.indexOf(".") !== -1) {


This doesn't check for other things like scientific notation (1000000000000000000000000000e1), but you can't do a simple indexOf on e because you don't want to allow 0xbeef.

DanielRosenwasser · 2019-09-03T18:46:57Z

src/compiler/diagnosticMessages.json

        "category": "Error",
        "code": 1356
    },
+    "Numeric literals with absolute values equal to 2^53 or greater are too large to be represented accurately as an integer.": {


as integers

typescript-bot · 2019-09-03T18:52:15Z

Hey @DanielRosenwasser, I've packed this into an installable tgz. You can install it for testing by referencing it in your package.json like so:

{
    "devDependencies": {
        "typescript": "https://typescript.visualstudio.com/cf7ac146-d525-443c-b23c-0d58337efebc/_apis/build/builds/42584/artifacts?artifactName=tgz&fileId=A372393C0D8B45276B7E5306D2299C13901FF09D6ED421C8CD2A7823D89DBE4202&fileName=/typescript-3.7.0-insiders.20190903.tgz"
    }
}

and then running npm install.

typescript-bot · 2019-09-03T19:06:40Z

The user suite test run you requested has finished and failed. I've opened a PR with the baseline diff from master.

JoshuaKGoldberg · 2019-09-03T20:15:55Z

src/compiler/checker.ts

+                return false;
+            }
+
+            return Number(text) >= Math.pow(2, 53) - 1;


Hmm, per the user baselines, should allow 9007199254740991 as 2**53. Will update...

Suggested change

return Number(text) >= Math.pow(2, 53) - 1;

return Number(text) >= 2 ** 53;

IE does not have the exponentiation operator, according to mdn

it gets downleveled

Right. I forgot TS down levels syntax, but not methods.

DanielRosenwasser · 2019-09-03T20:59:37Z

Turns out this breaks more than we thought. For example, it breaks the Azure SDK with the integer 621355968000000000: https://github.com/Azure/azure-sdk-for-js/blob/dcd9a29b083a63fa1c9888aca4a5da6acda425a6/sdk/servicebus/service-bus/src/util/utils.ts#L106

(@bterlson @ramya-rao-a)

The thing that's interesting is that while almost any operation on that number is lossy, I believe that the numeric literal hasn't lost any precision. That's because the mantissa 621355968 can be accurately represented.

DanielRosenwasser · 2019-09-03T21:54:27Z

I guess you can shave off the trailing 0s and see if the number fits, but I'm increasingly convinced that this has more value as a lint rule, and that putting it into TypeScript with the intent of only catching a subset of suspicious code would be worse than having it built into ESLint.

JoshuaKGoldberg · 2019-09-03T22:05:32Z

In that case I'll close this PR and add a quickfix to add an n to numeric literal if it's all /\d+/ digits and >= 2 ** 53. Thanks!

JoshuaKGoldberg · 2019-09-11T00:41:23Z

#33300

typescript-bot · 2025-10-21T22:50:10Z

The TypeScript team hasn't accepted the linked issue #29863. If you can get it accepted, this PR will have a better chance of being reviewed.

Josh Goldberg added 3 commits September 2, 2019 23:10

Added error for numeric literals larger than 2^53 - 1

3c4898b

Updated constEnumErrors.errors.txt

ccb7f93

Always with the TSLint...

59f697a

Updated error message to mention negative values; added tests

281e7a4

DanielRosenwasser reviewed Sep 3, 2019

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typescript-bot mentioned this pull request Sep 3, 2019

🤖 User test baselines have changed for imprecise-numeric-literal-error JoshuaKGoldberg/TypeScript#1

Closed

JoshuaKGoldberg commented Sep 3, 2019

View reviewed changes

JoshuaKGoldberg closed this Sep 3, 2019

JoshuaKGoldberg deleted the imprecise-numeric-literal-error branch March 22, 2022 18:29

microsoft locked as resolved and limited conversation to collaborators Oct 21, 2025

	return Number(text) >= Math.pow(2, 53) - 1;
	return Number(text) >= 2 ** 53;

Added error for numeric literals larger than 2^53 - 1 #33202

Added error for numeric literals larger than 2^53 - 1 #33202

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