Fixes goto definitions for type predicates

Author: tinganho

src/compiler/checker.ts

@@ -11925,6 +11925,10 @@ namespace ts {
                 return resolveEntityName(<EntityName>entityName, meaning);
             }
 
+            if (entityName.parent.kind === SyntaxKind.TypePredicate) {
+                return resolveEntityName(<Identifier>entityName, /* meanings */ SymbolFlags.Variable);
+            }
+
             // Do we want to return undefined here?
             return undefined;
         }

tests/cases/fourslash/goToDefinitionTypePredicate.ts

@@ -0,0 +1,16 @@
+/// <reference path='fourslash.ts'/>
+
+//// /*classDeclaration*/class A {}
+//// function f(/*parameterDeclaration*/parameter: any): /*parameterName*/parameter is /*typeReference*/A {
+////     return typeof parameter === "string";
+//// }
+
+goTo.marker('parameterName');
+
+goTo.definition();
+verify.caretAtMarker('parameterDeclaration');
+
+goTo.marker('typeReference');
+
+goTo.definition();
+verify.caretAtMarker('classDeclaration');