goToDefinition: Don't add duplicate definitions for VariableDeclaration and ArrowFunction at f = () => {}

Author: Andy Hanson

src/services/goToDefinition.ts

@@ -32,7 +32,7 @@ namespace ts.GoToDefinition {
             const sigInfo = createDefinitionFromSignatureDeclaration(typeChecker, calledDeclaration);
             // For a function, if this is the original function definition, return just sigInfo.
             // If this is the original constructor definition, parent is the class.
-            if (typeChecker.getRootSymbols(symbol).some(s => calledDeclaration.symbol === s || calledDeclaration.symbol.parent === s) ||
+            if (typeChecker.getRootSymbols(symbol).some(s => symbolMatchesSignature(s, calledDeclaration)) ||
                 // TODO: GH#23742 Following check shouldn't be necessary if 'require' is an alias
                 symbol.declarations.some(d => isVariableDeclaration(d) && !!d.initializer && isRequireCall(d.initializer, /*checkArgumentIsStringLiteralLike*/ false))) {
                 return [sigInfo];
@@ -93,6 +93,15 @@ namespace ts.GoToDefinition {
         return getDefinitionFromSymbol(typeChecker, symbol, node);
     }
 
+    /**
+     * True if we should not add definitions for both the signature symbol and the definition symbol.
+     * True for `const |f = |() => 0`, false for `function |f() {} const |g = f;`.
+     */
+    function symbolMatchesSignature(s: Symbol, calledDeclaration: SignatureDeclaration) {
+        return s === calledDeclaration.symbol || s === calledDeclaration.symbol.parent ||
+            isVariableDeclaration(calledDeclaration.parent) && s === calledDeclaration.parent.symbol
+    }
+
     export function getReferenceAtPosition(sourceFile: SourceFile, position: number, program: Program): { fileName: string, file: SourceFile } | undefined {
         const referencePath = findReferenceInPosition(sourceFile.referencedFiles, position);
         if (referencePath) {

tests/cases/fourslash/goToDefinitionSignatureAlias.ts

@@ -8,8 +8,17 @@
 ////[|/*useG*/g|]();
 ////[|/*useH*/h|]();
 
+////const i = /*i*/() => 0;
+////const /*j*/j = i;
+
+////[|/*useI*/i|]();
+////[|/*useJ*/j|]();
+
 verify.goToDefinition({
     useF: "f",
     useG: ["g", "f"],
     useH: ["h", "f"],
+
+    useI: "i",
+    useJ: ["j", "i"],
 });