ESQL: Small fixes for COPY_SIGN

Adds some small fixes to `COPY_SIGN` and some docs and tests. The fixes
are mostly supporting the literal `NULL` in parameters. `COPY_SIGN`
supports `float` arguments, but the tests don't cover it because we
don't build `float` blocks. Otherwise, the tests are fairly standard.

Author: nik9000

docs/reference/query-languages/esql/_snippets/functions/description/copy_sign.md

@@ -5,6 +5,7 @@
 * [`ATAN2`](../../functions-operators/math-functions.md#esql-atan2)
 * [`CBRT`](../../functions-operators/math-functions.md#esql-cbrt)
 * [`CEIL`](../../functions-operators/math-functions.md#esql-ceil)
+* [`COPY_SIGN`](../../functions-operators/math-functions.md#esql-copy-sign)
 * [`COS`](../../functions-operators/math-functions.md#esql-cos)
 * [`COSH`](../../functions-operators/math-functions.md#esql-cosh)
 * [`E`](../../functions-operators/math-functions.md#esql-e)

docs/reference/query-languages/esql/_snippets/functions/layout/copy_sign.md

@@ -33,6 +33,9 @@ mapped_pages:
 :::{include} ../_snippets/functions/layout/ceil.md
 :::
 
+:::{include} ../_snippets/functions/layout/copy_sign.md
+:::
+
 :::{include} ../_snippets/functions/layout/cos.md
 :::
 

docs/reference/query-languages/esql/_snippets/functions/parameters/copy_sign.md

@@ -15,6 +15,7 @@
 import org.elasticsearch.xpack.esql.EsqlIllegalArgumentException;
 import org.elasticsearch.xpack.esql.core.expression.Expression;
 import org.elasticsearch.xpack.esql.core.expression.Expressions;
+import org.elasticsearch.xpack.esql.core.expression.TypeResolutions;
 import org.elasticsearch.xpack.esql.core.tree.NodeInfo;
 import org.elasticsearch.xpack.esql.core.tree.Source;
 import org.elasticsearch.xpack.esql.core.type.DataType;
@@ -63,18 +64,18 @@ EvalOperator.ExpressionEvaluator.Factory create(
     @FunctionInfo(
         description = "Returns a value with the magnitude of the first argument and the sign of the second argument. "
             + "This function is similar to Java's Math.copySign(double magnitude, double sign).",
-        returnType = { "double", "float" }
+        returnType = { "double", "integer", "long" }
     )
     public CopySign(
         Source source,
         @Param(
             name = "magnitude",
-            type = { "double", "float", "integer", "long" },
+            type = { "double", "integer", "long" },
             description = "The expression providing the magnitude of the result. Must be a numeric type."
         ) Expression magnitude,
         @Param(
             name = "sign",
-            type = { "double", "float", "integer", "long" },
+            type = { "double", "integer", "long" },
             description = "The expression providing the sign of the result. Must be a numeric type."
         ) Expression sign
     ) {
@@ -125,11 +126,25 @@ public TypeResolution resolveType() {
         }
         var magnitude = children().get(0);
         var sign = children().get(1);
-        if (magnitude.dataType().isNumeric() == false) {
-            return new TypeResolution("Magnitude must be a numeric type");
+        TypeResolution resolution = TypeResolutions.isType(
+            magnitude,
+            t -> t.isNumeric() && t != DataType.UNSIGNED_LONG,
+            sourceText(),
+            TypeResolutions.ParamOrdinal.FIRST,
+            "numeric"
+        );
+        if (resolution.unresolved()) {
+            return resolution;
         }
-        if (sign.dataType().isNumeric() == false) {
-            return new TypeResolution("Sign must be a numeric type");
+        resolution = TypeResolutions.isType(
+            sign,
+            t -> t.isNumeric() && t != DataType.UNSIGNED_LONG,
+            sourceText(),
+            TypeResolutions.ParamOrdinal.SECOND,
+            "numeric"
+        );
+        if (resolution.unresolved()) {
+            return resolution;
         }
         // The return type is the same as the magnitude type, so we can use it directly.
         dataType = magnitude.dataType();