Try to grab parameters for single-declaration variable statements.

We only do this for a (parenthesized) function expression, arrow function, or class expression with a constructor. In the presence of a class expression, if there are multiple constructor declarations, the parameters are acquired from the first one.

Author: DanielRosenwasser

src/services/services.ts

@@ -7059,7 +7059,7 @@ namespace ts {
  return undefined;
  }
 
- let parameters = isFunctionLike(commentOwner) ? commentOwner.parameters : emptyArray;
+ let parameters = getParametersForJsDocOwningNode(commentOwner);
  let posLineAndChar = sourceFile.getLineAndCharacterOfPosition(position);
  let lineStart = sourceFile.getLineStarts()[posLineAndChar.line];
 
@@ -7096,6 +7096,52 @@ namespace ts {
  return { newText: result, caretOffset: preamble.length };
  }
 
+ function getParametersForJsDocOwningNode(commentOwner: Node): ParameterDeclaration[] {
+ if (isFunctionLike(commentOwner)) {
+ return commentOwner.parameters;
+ }
+
+ if (commentOwner.kind === SyntaxKind.VariableStatement) {
+ const varStatement = <VariableStatement>commentOwner;
+ const varDeclarations = varStatement.declarationList.declarations;
+
+ if (varDeclarations.length === 1 && varDeclarations[0].initializer) {
+ return getParametersFromRightHandSideOfAssignment(varDeclarations[0].initializer);
+ }
+ }
+
+ return emptyArray;
+ }
+
+ /**
+ * Digs into an an initializer or RHS operand of an assignment operation
+ * to get the parameters from an apst signature corresponding to a
+ * function expression or a class expression.
+ *
+ * @param rightHandSide the expression which may contain an appropriate set of parameters
+ * @returns the parameters of a signature found on the RHS if one exists; otherwise 'emptyArray'.
+ */
+ function getParametersFromRightHandSideOfAssignment(rightHandSide: Expression): ParameterDeclaration[] {
+ while (rightHandSide.kind === SyntaxKind.ParenthesizedExpression) {
+ rightHandSide = (<ParenthesizedExpression>rightHandSide).expression;
+ }
+
+ switch (rightHandSide.kind) {
+ case SyntaxKind.FunctionExpression:
+ case SyntaxKind.ArrowFunction:
+ return (<FunctionExpression>rightHandSide).parameters;
+ case SyntaxKind.ClassExpression:
+ for (let member of (<ClassExpression>rightHandSide).members) {
+ if (member.kind === SyntaxKind.Constructor) {
+ return (<ConstructorDeclaration>member).parameters;
+ }
+ }
+ break;
+ }
+
+ return emptyArray;
+ }
+
  function getTodoComments(fileName: string, descriptors: TodoCommentDescriptor[]): TodoComment[] {
  // Note: while getting todo comments seems like a syntactic operation, we actually
  // treat it as a semantic operation here. This is because we expect our host to call