feat: Catch more unsafe numbers

Flag subnormals, numbers that are flushed to zero,
and overly-large integers.

Refs eslint#68

src/rules/no-unsafe-values.js

@@ -3,6 +3,10 @@
  * @author Bradley Meck Farias
  */
 
+// These numbers evaluated to zero unexpectedly.  If the group's digits
+// are all zero, that's fine.
+const SMALL_NUMBERS = [/\.(\d+)/u, /((?:\d+\.)?\d+)e/iu];
+
 export default {
 	meta: {
 		type: /** @type {const} */ ("problem"),
@@ -13,6 +17,8 @@ export default {
 
 		messages: {
 			unsafeNumber: "Number outside safe range found.",
+			unsafeInteger: "Integer outside safe range found.",
+			subnormal: "Subnormal numbers are outside the safe range.",
 			loneSurrogate: "Lone surrogate '{{ surrogate }}' found.",
 		},
 	},
@@ -25,6 +31,48 @@ export default {
 						loc: node.loc,
 						messageId: "unsafeNumber",
 					});
+				} else {
+					const txt = context.sourceCode.getText(node);
+					if (node.value === 0) {
+						// If the value has been rounded down to 0, but there was some fraction
+						// or non-zero part before an e-, this is a very small number that doesn't
+						// fit inside an f64.
+						for (const r of SMALL_NUMBERS) {
+							const m = txt.match(r);
+							// If the digits are all 0, it's ok.
+							if (m?.[1]?.match(/[1-9]/u)) {
+								context.report({
+									loc: node.loc,
+									messageId: "unsafeNumber",
+								});
+								break;
+							}
+						}
+					} else if (!txt.match(/[.e]/iu)) {
+						// Intended to be an integer
+						if (
+							node.value > Number.MAX_SAFE_INTEGER ||
+							node.value < Number.MIN_SAFE_INTEGER
+						) {
+							context.report({
+								loc: node.loc,
+								messageId: "unsafeInteger",
+							});
+						}
+					} else {
+						// Floating point.  Check for subnormal.
+						const ab = new ArrayBuffer(8);
+						const dv = new DataView(ab);
+						dv.setFloat64(0, node.value, false);
+						const bi = dv.getBigUint64(0, false);
+						// Subnormals have an 11-bit exponent of 0 and a non-zero mantissa.
+						if ((bi & 0x7ff0000000000000n) === 0n) {
+							context.report({
+								loc: node.loc,
+								messageId: "subnormal",
+							});
+						}
+					}
 				}
 			},
 			String(node) {

tests/rules/no-unsafe-values.test.js

@@ -131,5 +131,113 @@ ruleTester.run("no-unsafe-values", rule, {
 				},
 			],
 		},
+		{
+			code: "1e-400",
+			errors: [
+				{
+					messageId: "unsafeNumber",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 7,
+				},
+			],
+		},
+		{
+			code: "-1e-400",
+			errors: [
+				{
+					messageId: "unsafeNumber",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 8,
+				},
+			],
+		},
+		{
+			code: "0.01e-400",
+			errors: [
+				{
+					messageId: "unsafeNumber",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 10,
+				},
+			],
+		},
+		{
+			code: "-10.2e-402",
+			errors: [
+				{
+					messageId: "unsafeNumber",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 11,
+				},
+			],
+		},
+		{
+			code: `0.${"0".repeat(400)}1`,
+			errors: [
+				{
+					messageId: "unsafeNumber",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 404,
+				},
+			],
+		},
+		{
+			code: "9007199254740992",
+			errors: [
+				{
+					messageId: "unsafeInteger",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 17,
+				},
+			],
+		},
+		{
+			code: "-9007199254740992",
+			errors: [
+				{
+					messageId: "unsafeInteger",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 18,
+				},
+			],
+		},
+		{
+			code: "2.2250738585072009e-308",
+			errors: [
+				{
+					messageId: "subnormal",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 24,
+				},
+			],
+		},
+		{
+			code: "-2.2250738585072009e-308",
+			errors: [
+				{
+					messageId: "subnormal",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 25,
+				},
+			],
+		},
 	],
 });