Fix type-checking with COALESCE (#19157)

frontend/src/metabase/lib/expressions/typechecker.js

@@ -78,7 +78,11 @@ export function typeCheck(cst, rootType) {
       if (type === "number") {
         const op = getMBQLName(name);
         const returnType = MBQL_CLAUSES[op].type;
-        if (returnType !== "number" && returnType !== "string") {
+        if (
+          returnType !== "number" &&
+          returnType !== "string" &&
+          returnType !== "expression"
+        ) {
           const message = t`Expecting ${type} but found function ${name} returning ${returnType}`;
           this.errors.push({ message });
         }

frontend/test/metabase/lib/expressions/typechecker.unit.spec.js

@@ -190,6 +190,10 @@ describe("type-checker", () => {
       expect(() => validate("Lower([State]) > 'AB'")).not.toThrow();
     });
 
+    it("should allow a comparison on the result of COALESCE", () => {
+      expect(() => validate("Coalesce([X],[Y]) > 0")).not.toThrow();
+    });
+
     it("should reject a less/greater comparison on functions returning boolean", () => {
       expect(() => validate("IsEmpty([Tax]) < 5")).toThrow();
       expect(() => validate("IsEmpty([Tax]) >= 0")).toThrow();