lib: add Math.sumPrecise type definition (ES2025)

[kamalkarki111]

Summary

Adds type definition for Math.sumPrecise which is part of the TC39 proposal-math-sum that reached Stage 4 on 2025-07-28, making it part of ES2026.

Changes

• New file: src/lib/esnext.math.d.ts — extends interface Math with sumPrecise
• Updated src/lib/esnext.d.ts — added /// <reference lib="esnext.math" />
• Updated src/lib/libs.json — registered esnext.math in the libs array
• Updated src/compiler/commandLineParser.ts — mapped esnext.math lib name to file
• Updated src/compiler/utilities.ts — added sumPrecise to ScriptTargetFeatures for helpful diagnostics

Why esnext, not es2025?

The proposal reached Stage 4 on 2025-07-28, one month after ES2025 was finalized (June 2025), so it will be included in ES2026. TypeScript does not have es2026 lib files yet, so esnext is the correct placement for now.

Runtime support

Runtime	Supported
Firefox 137+	✅
Safari 18.4 (JavaScriptCore)	✅
Bun	✅
V8 / Node.js / Chrome	❌ not yet

References

• TC39 Proposal: https://github.com/tc39/proposal-math-sum
• Stage 4 meeting notes: https://github.com/tc39/notes/blob/main/meetings/2025-07/july-28.md#mathsumprecise-for-stage-4
• MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/sumPrecise

Based on the same changes as #63429

[typescript-automation]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[typescript-automation]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[Copilot]

Pull request overview

Adds a new esnext lib slice for the Stage 4 Math.sumPrecise proposal and wires it into lib selection, diagnostics, and conformance coverage.

Changes:

• Introduces src/lib/esnext.math.d.ts to declare Math.sumPrecise(numbers: Iterable<number>): number.
• Registers the new lib name (esnext.math) and ensures it is reachable via /// <reference lib="..."> and --lib.
• Adds a conformance test plus updated baselines reflecting the new --lib option value.

Reviewed changes

Copilot reviewed 14 out of 19 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/cases/conformance/esnext/mathSumPrecise.ts	New conformance test exercising Math.sumPrecise typing under @lib: esnext.
tests/baselines/reference/mathSumPrecise.types	New baseline validating inferred types for the conformance test.
tests/baselines/reference/mathSumPrecise.symbols	New baseline validating symbol resolution for Math.sumPrecise.
tests/baselines/reference/config/convertCompilerOptionsFromJson/Convert trailing-whitespace string option of libs to compiler-options with jsonSourceFile api.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/convertCompilerOptionsFromJson/Convert trailing-whitespace string option of libs to compiler-options with json api.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/convertCompilerOptionsFromJson/Convert incorrect option of libs to compiler-options with jsonSourceFile api.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/convertCompilerOptionsFromJson/Convert incorrect option of libs to compiler-options with json api.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/convertCompilerOptionsFromJson/Convert empty string option of libs to compiler-options with jsonSourceFile api.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/convertCompilerOptionsFromJson/Convert empty string option of libs to compiler-options with json api.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/convertCompilerOptionsFromJson/Convert empty string option of libs array to compiler-options with jsonSourceFile api.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/convertCompilerOptionsFromJson/Convert empty string option of libs array to compiler-options with json api.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/commandLineParsing/parseCommandLine/Parse invalid option of library flags.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/commandLineParsing/parseCommandLine/Parse --lib option with trailing white-space.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
tests/baselines/reference/config/commandLineParsing/parseCommandLine/Parse --lib option with extra comma.js	Baseline update to include esnext.math in TS6046 allowed --lib values.
src/lib/libs.json	Registers esnext.math in the known lib-name list.
src/lib/esnext.math.d.ts	New lib slice adding the Math.sumPrecise declaration.
src/lib/esnext.d.ts	Ensures esnext includes esnext.math via a lib reference.
src/compiler/utilities.ts	Adds sumPrecise to ScriptTargetFeatures for Math under esnext (used for lib/target suggestion diagnostics).
src/compiler/commandLineParser.ts	Maps --lib esnext.math to lib.esnext.math.d.ts.

Files not reviewed (3)

• tests/baselines/reference/config/commandLineParsing/parseCommandLine/Parse --lib option with extra comma.js: Generated file
• tests/baselines/reference/config/commandLineParsing/parseCommandLine/Parse --lib option with trailing white-space.js: Generated file
• tests/baselines/reference/config/commandLineParsing/parseCommandLine/Parse invalid option of library flags.js: Generated file

[MartinJohns]

Duplicate of #63429.