Editorial: Rewrite duration grammar to avoid extra fraction checks

Suggested by Anba, this is an editorial improvement to make Duration
strings like PT3.5H40M (where a component with a fractional part is
followed by another component) invalid according to the ISO 8601 grammar.

Previously, such strings were valid according to the grammar, but weeded
out with an extra check.

In order to test the new grammar productions, brings validStrings.mjs up
to date. Previously, support for minute and hour fractional parts had been
left out of validStrings.mjs altogether.

There are already tests for the invalid strings in test262.

Closes: #2282

UPSTREAM_COMMIT=2b21aa1b26da178b2fe179ec4c0379945c9edd61

Author: ptomato

test/validStrings.mjs

@@ -341,31 +341,46 @@ const annotatedMonthDay = withSyntaxConstraints(
   }
 );
 
-const durationFraction = withCode(fraction, (data, result) => {
+const durationSecondsFraction = withCode(fraction, (data, result) => {
   result = result.slice(1);
   const fraction = result.padEnd(9, '0');
   data.milliseconds = +fraction.slice(0, 3) * data.factor;
   data.microseconds = +fraction.slice(3, 6) * data.factor;
   data.nanoseconds = +fraction.slice(6, 9) * data.factor;
 });
+const durationMinutesFraction = withCode(fraction, (data, result) => {
+  result = result.slice(1);
+  const ns = +result.padEnd(9, '0') * 60;
+  data.seconds = Math.trunc(ns / 1e9) * data.factor;
+  data.milliseconds = Math.trunc((ns % 1e9) / 1e6) * data.factor;
+  data.microseconds = Math.trunc((ns % 1e6) / 1e3) * data.factor;
+  data.nanoseconds = Math.trunc(ns % 1e3) * data.factor;
+});
+const durationHoursFraction = withCode(fraction, (data, result) => {
+  result = result.slice(1);
+  const ns = +result.padEnd(9, '0') * 3600;
+  data.minutes = Math.trunc(ns / 6e10) * data.factor;
+  data.seconds = Math.trunc((ns % 6e10) / 1e9) * data.factor;
+  data.milliseconds = Math.trunc((ns % 1e9) / 1e6) * data.factor;
+  data.microseconds = Math.trunc((ns % 1e6) / 1e3) * data.factor;
+  data.nanoseconds = Math.trunc(ns % 1e3) * data.factor;
+});
 
 const digitsNotInfinite = withSyntaxConstraints(oneOrMore(digit()), (result) => {
   if (!Number.isFinite(+result)) throw new SyntaxError('try again on infinity');
 });
 const durationSeconds = seq(
   withCode(digitsNotInfinite, (data, result) => (data.seconds = +result * data.factor)),
-  [durationFraction],
+  [durationSecondsFraction],
   secondsDesignator
 );
 const durationMinutes = seq(
   withCode(digitsNotInfinite, (data, result) => (data.minutes = +result * data.factor)),
-  minutesDesignator,
-  [durationSeconds]
+  choice(seq(minutesDesignator, [durationSeconds]), seq(durationMinutesFraction, minutesDesignator))
 );
 const durationHours = seq(
   withCode(digitsNotInfinite, (data, result) => (data.hours = +result * data.factor)),
-  hoursDesignator,
-  [choice(durationMinutes, durationSeconds)]
+  choice(seq(hoursDesignator, [choice(durationMinutes, durationSeconds)]), seq(durationHoursFraction, hoursDesignator))
 );
 const durationTime = seq(timeDesignator, choice(durationHours, durationMinutes, durationSeconds));
 const durationDays = seq(