Fix: Exclude generator functions from convert-to-class suggestions

Co-authored-by: RyanCavanaugh <6685088+RyanCavanaugh@users.noreply.github.com>

src/services/suggestionDiagnostics.ts

@@ -289,21 +289,31 @@ function getKeyFromNode(exp: FunctionLikeDeclaration) {
     return `${exp.pos.toString()}:${exp.end.toString()}`;
 }
 
-function canBeConvertedToClass(node: Node, checker: TypeChecker): boolean {
-    if (isFunctionExpression(node)) {
-        if (isVariableDeclaration(node.parent) && node.symbol.members?.size) {
-            return true;
-        }
-
-        const symbol = checker.getSymbolOfExpando(node, /*allowDeclaration*/ false);
-        return !!(symbol && (symbol.exports?.size || symbol.members?.size));
-    }
-
-    if (isFunctionDeclaration(node)) {
-        return !!node.symbol.members?.size;
-    }
-
-    return false;
+function canBeConvertedToClass(node: Node, checker: TypeChecker): boolean {
+    if (isFunctionExpression(node)) {
+        // Generator functions cannot be converted to classes
+        if (getFunctionFlags(node) & FunctionFlags.Generator) {
+            return false;
+        }
+
+        if (isVariableDeclaration(node.parent) && node.symbol.members?.size) {
+            return true;
+        }
+
+        const symbol = checker.getSymbolOfExpando(node, /*allowDeclaration*/ false);
+        return !!(symbol && (symbol.exports?.size || symbol.members?.size));
+    }
+
+    if (isFunctionDeclaration(node)) {
+        // Generator functions cannot be converted to classes
+        if (getFunctionFlags(node) & FunctionFlags.Generator) {
+            return false;
+        }
+
+        return !!node.symbol.members?.size;
+    }
+
+    return false;
 }
 
 /** @internal */

tests/cases/fourslash/convertFunctionToEs6Class_generatorExpression_falsePositive.ts

@@ -0,0 +1,10 @@
+/// <reference path='fourslash.ts' />
+
+// @allowJs: true
+// @Filename: /a.js
+////const gen = function*() {};
+////gen.prototype.next = gen.prototype.next;
+////gen.prototype.return = gen.prototype.return;
+
+// Generator function expressions should not trigger the convert-to-class suggestion
+verify.getSuggestionDiagnostics([]);

tests/cases/fourslash/convertFunctionToEs6Class_generator_falsePositive.ts

@@ -0,0 +1,10 @@
+/// <reference path='fourslash.ts' />
+
+// @allowJs: true
+// @Filename: /a.js
+////function* gen() {}
+////gen.prototype.next = gen.prototype.next;
+////gen.prototype.return = gen.prototype.return;
+
+// Generator functions should not trigger the convert-to-class suggestion
+verify.getSuggestionDiagnostics([]);

tests/cases/fourslash/convertFunctionToEs6Class_regularVsGenerator.ts

@@ -0,0 +1,17 @@
+/// <reference path='fourslash.ts' />
+
+// @allowJs: true
+// @Filename: /a.js
+////function [|regular|]() {}
+////regular.prototype.method = function() { this.x = 1; };
+////
+////function* gen() {}
+////gen.prototype.next = gen.prototype.next;
+////gen.prototype.return = gen.prototype.return;
+
+// Regular constructor functions should still trigger the convert-to-class suggestion
+// but generator functions should not
+verify.getSuggestionDiagnostics([{
+    message: "This constructor function may be converted to a class declaration.",
+    code: 80002,
+}]);