Fix indexing constructors with generic parameters

Previously in the case of a constructor like `A<Int>(value: 1)`
`Fn->getLoc()` returned the location of `>(value: 1)` while the actual
location we're looking for is correctly the start of `A<Int>(value: 1)`.
This adjusts the location we're looking up to use the start location of
the constructor instead.

Fixes: #54532

Author: keith

lib/IDE/SourceEntityWalker.cpp

@@ -815,9 +815,9 @@ passReference(ValueDecl *D, Type Ty, SourceLoc BaseNameLoc, SourceRange Range,
 
   if (auto *TD = dyn_cast<TypeDecl>(D)) {
     if (!CtorRefs.empty() && BaseNameLoc.isValid()) {
-      Expr *Fn = CtorRefs.back()->getFn();
-      if (Fn->getLoc() == BaseNameLoc) {
-        D = ide::getReferencedDecl(Fn).second.getDecl();
+      ConstructorRefCallExpr *Ctor = CtorRefs.back();
+      if (Ctor->getStartLoc() == BaseNameLoc) {
+        D = ide::getReferencedDecl(Ctor->getFn()).second.getDecl();
         if (D == nullptr) {
           assert(false && "Unhandled constructor reference");
           return true;

test/Index/index_generic_params.swift

@@ -86,3 +86,17 @@ extension Wrapper2.NonGenericWrapped where Wrapper2Param: P1 {
 extension MyUnknownType where Wrapper2Param: P1 {
   func foo(x: Wrapper2Param) {}
 }
+
+// MARK: - Test indexing a generic initializer
+
+struct A<T> { // CHECK: [[@LINE]]:8 | struct/Swift | A | [[A_USR:.*]] | Def | rel: 0
+  init(value: T) {} // CHECK: [[@LINE]]:3 | constructor/Swift | init(value:) | [[A_init_USR:.*]] | Def,RelChild | rel: 1
+}
+
+// CHECK: [[@LINE+2]]:5 | struct/Swift | A | [[A_USR]] | Ref | rel: 0
+// CHECK: [[@LINE+1]]:5 | constructor/Swift | init(value:) | [[A_init_USR]] | Ref,Call | rel: 0
+_ = A(value: 1)
+// CHECK: [[@LINE+3]]:5 | struct/Swift | A | [[A_USR]] | Ref | rel: 0
+// CHECK: [[@LINE+2]]:5 | constructor/Swift | init(value:) | [[A_init_USR]] | Ref,Call | rel: 0
+// CHECK: [[@LINE+1]]:7 | struct/Swift | Int | s:Si | Ref | rel: 0
+_ = A<Int>(value: 1)