Sqrt calc function implementation

lib/src/ast/sass/expression/calculation.dart

@@ -50,6 +50,10 @@ class CalculationExpression implements Expression {
     }
   }
 
+  /// Returns a `sqrt()` calculation expression.
+  CalculationExpression.sqrt(Expression argument, FileSpan span)
+      : this("sqrt", [argument], span);
+
   /// Returns a `clamp()` calculation expression.
   CalculationExpression.clamp(
       Expression min, Expression value, Expression max, FileSpan span)

lib/src/functions/math.dart

@@ -12,6 +12,7 @@ import '../deprecation.dart';
 import '../evaluation_context.dart';
 import '../exception.dart';
 import '../module/built_in.dart';
+import '../util/number.dart';
 import '../value.dart';
 
 /// The global definitions of Sass math functions.
@@ -144,11 +145,7 @@ final _pow = _function("pow", r"$base, $exponent", (arguments) {
 
 final _sqrt = _function("sqrt", r"$number", (arguments) {
   var number = arguments[0].assertNumber("number");
-  if (number.hasUnits) {
-    throw SassScriptException("\$number: Expected $number to have no units.");
-  } else {
-    return SassNumber(math.sqrt(number.value));
-  }
+  return sqrt(number);
 });
 
 ///

lib/src/parse/stylesheet.dart

@@ -2894,6 +2894,7 @@ abstract class StylesheetParser extends Parser {
     assert(scanner.peekChar() == $lparen);
     switch (name) {
       case "calc":
+      case "sqrt":
         var arguments = _calculationArguments(1);
         return CalculationExpression(name, arguments, scanner.spanFrom(start));
 

lib/src/util/number.dart

@@ -118,3 +118,9 @@ double moduloLikeSass(double num1, double num2) {
   var result = num1 % num2;
   return result == 0 ? 0 : result + num2;
 }
+
+/// Return square root of [number]
+SassNumber sqrt(SassNumber number) {
+  number.assertNoUnits();
+  return SassNumber(math.sqrt(number.value));
+}

lib/src/value/calculation.dart

@@ -6,7 +6,7 @@ import 'package:meta/meta.dart';
 
 import '../exception.dart';
 import '../util/nullable.dart';
-import '../util/number.dart';
+import '../util/number.dart' as number;
 import '../utils.dart';
 import '../value.dart';
 import '../visitor/interface/value.dart';
@@ -120,6 +120,23 @@ class SassCalculation extends Value {
     return SassCalculation._("max", args);
   }
 
+  /// Creates a `sqrt()` calculation with the given [argument].
+  ///
+  /// Each argument must be either a [SassNumber], a [SassCalculation], an
+  /// unquoted [SassString], a [CalculationOperation], or a
+  /// [CalculationInterpolation]. It must be passed at least one argument.
+  ///
+  /// This automatically simplifies the calculation, so it may return a
+  /// [SassNumber] rather than a [SassCalculation]. It throws an exception if it
+  /// can determine that the calculation will definitely produce invalid CSS.
+  static Value sqrt(Object argument) {
+    argument = _simplify(argument);
+    if (argument is! SassNumber) {
+      return SassCalculation._("sqrt", [argument]);
+    }
+    return number.sqrt(argument);
+  }
+
   /// Creates a `clamp()` calculation with the given [min], [value], and [max].
   ///
   /// Each argument must be either a [SassNumber], a [SassCalculation], an
@@ -202,7 +219,7 @@ class SassCalculation extends Value {
 
       _verifyCompatibleNumbers([left, right]);
 
-      if (right is SassNumber && fuzzyLessThan(right.value, 0)) {
+      if (right is SassNumber && number.fuzzyLessThan(right.value, 0)) {
         right = right.times(SassNumber(-1));
         operator = operator == CalculationOperator.plus
             ? CalculationOperator.minus

lib/src/visitor/async_evaluate.dart

@@ -2303,6 +2303,9 @@ class _EvaluateVisitor
         case "calc":
           assert(arguments.length == 1);
           return SassCalculation.calc(arguments[0]);
+        case "sqrt":
+          assert(arguments.length == 1);
+          return SassCalculation.sqrt(arguments[0]);
         case "min":
           return SassCalculation.min(arguments);
         case "max":

lib/src/visitor/evaluate.dart

@@ -2292,6 +2292,9 @@ class _EvaluateVisitor
         case "calc":
           assert(arguments.length == 1);
           return SassCalculation.calc(arguments[0]);
+        case "sqrt":
+          assert(arguments.length == 1);
+          return SassCalculation.sqrt(arguments[0]);
         case "min":
           return SassCalculation.min(arguments);
         case "max":