feat(go_indexer): emit tapps for instantiated Named types (#5158)

kythe/go/indexer/emit.go

@@ -168,6 +168,10 @@ func (pi *PackageInfo) Emit(ctx context.Context, sink Sink, opts *EmitOptions) e
 				e.visitRangeStmt(n, stack)
 			case *ast.CompositeLit:
 				e.visitCompositeLit(n, stack)
+			case *ast.IndexExpr:
+				e.visitIndexExpr(n, stack)
+			case *ast.IndexListExpr:
+				e.visitIndexListExpr(n, stack)
 			}
 			return true
 		}), file)
@@ -223,7 +227,14 @@ func (e *emitter) visitIdent(id *ast.Ident, stack stackFunc) {
 		return
 	}
 
-	target := e.pi.ObjectVName(obj)
+	var target *spb.VName
+	if n, ok := obj.(*types.TypeName); ok && obj.Pkg() == nil {
+		// Handle type arguments in instantiated types.
+		target = e.emitType(n.Type())
+	} else {
+		target = e.pi.ObjectVName(obj)
+	}
+
 	if target == nil {
 		// This should not happen in well-formed packages, but can if the
 		// extractor gets confused. Avoid emitting confusing references in such
@@ -293,7 +304,7 @@ func (e *emitter) visitFuncDecl(decl *ast.FuncDecl, stack stackFunc) {
 // with given constructor and parameters.  The constructor's kind is also
 // emitted if this is the first time seeing it.
 func (e *emitter) emitTApp(ms *cpb.MarkedSource, ctorKind string, ctor *spb.VName, params ...*spb.VName) *spb.VName {
-	if e.pi.typeEmitted.Add(ctor.Signature) {
+	if ctorKind != "" && e.pi.typeEmitted.Add(ctor.Signature) {
 		e.writeFact(ctor, facts.NodeKind, ctorKind)
 		if ctorKind == nodes.TBuiltin {
 			e.emitBuiltinMarkedSource(ctor)
@@ -330,7 +341,18 @@ func (e *emitter) emitType(typ types.Type) *spb.VName {
 
 	switch typ := typ.(type) {
 	case *types.Named:
-		v = e.pi.ObjectVName(typ.Obj())
+		if typ.TypeArgs().Len() == 0 {
+			v = e.pi.ObjectVName(typ.Obj())
+		} else {
+			// Instantiated Named types produce tapps
+			ctor := e.emitType(typ.Origin())
+			args := typ.TypeArgs()
+			var params []*spb.VName
+			for i := 0; i < args.Len(); i++ {
+				params = append(params, e.emitType(args.At(i)))
+			}
+			v = e.emitTApp(genericTAppMS, "", ctor, params...)
+		}
 	case *types.Basic:
 		v = govname.BasicType(typ)
 		if e.pi.typeEmitted.Add(v.Signature) {
@@ -694,6 +716,22 @@ func (e *emitter) visitCompositeLit(expr *ast.CompositeLit, stack stackFunc) {
 	}
 }
 
+// visitIndexExpr handles references to instantiated types with a single type
+// parameter.
+func (e *emitter) visitIndexExpr(expr *ast.IndexExpr, stack stackFunc) {
+	if n, ok := e.pi.Info.TypeOf(expr).(*types.Named); ok && n.TypeArgs().Len() > 0 {
+		e.writeRef(expr, e.emitType(n), edges.Ref)
+	}
+}
+
+// visitIndexListExpr handles references to instantiated types with multiple
+// type parameters.
+func (e *emitter) visitIndexListExpr(expr *ast.IndexListExpr, stack stackFunc) {
+	if n, ok := e.pi.Info.TypeOf(expr).(*types.Named); ok && n.TypeArgs().Len() > 0 {
+		e.writeRef(expr, e.emitType(n), edges.Ref)
+	}
+}
+
 // emitPosRef emits an anchor spanning loc, pointing to obj.
 func (e *emitter) emitPosRef(loc ast.Node, obj types.Object, kind string) {
 	target := e.pi.ObjectVName(obj)

kythe/go/indexer/markedsource.go

@@ -334,6 +334,22 @@ var (
 		}},
 		PreText: "<-chan ",
 	}
+	genericTAppMS = &cpb.MarkedSource{
+		Kind: cpb.MarkedSource_TYPE,
+		Child: []*cpb.MarkedSource{{
+			Kind:        cpb.MarkedSource_LOOKUP_BY_PARAM,
+			LookupIndex: 0,
+		}, {
+			Kind:     cpb.MarkedSource_BOX,
+			PreText:  "[",
+			PostText: "]",
+			Child: []*cpb.MarkedSource{{
+				Kind:        cpb.MarkedSource_PARAMETER_LOOKUP_BY_PARAM,
+				LookupIndex: 1,
+			}},
+			PostChildText: ", ",
+		}},
+	}
 )
 
 func arrayTAppMS(length int64) *cpb.MarkedSource {

kythe/go/indexer/testdata/generics/genericmethod.go

@@ -1,7 +1,6 @@
 package genericmethod
 
 func main() {
-	//- @Container ref Container
 	c := &Container[string]{"element"}
 	//- @Get ref Get
 	c.Get()

kythe/go/indexer/testdata/generics/genericstruct.go

@@ -1,5 +1,25 @@
 package genericstruct
 
+func main() {
+	//- @"Container[string]" ref ContainerApp
+	//- @Container ref Container
+	//- @string ref String
+	_ = &Container[string]{"element"}
+	//- ContainerApp.node/kind "tapp"
+	//- ContainerApp param.0 Container
+	//- ContainerApp param.1 String
+
+	//- @"Pair[string, int]" ref PairApp
+	//- @Pair ref Pair
+	//- @string ref String
+	//- @int ref Int
+	_ = &Pair[string, int]{"first", 2}
+	//- PairApp.node/kind "tapp"
+	//- PairApp param.0 Pair
+	//- PairApp param.1 String
+	//- PairApp param.2 Int
+}
+
 //- @Container defines/binding Container
 //- Container.node/kind record
 //- @T defines/binding TVar
@@ -11,13 +31,16 @@ type Container[T any] struct {
 }
 
 //- @T defines/binding TVar2
+//- @U defines/binding UVar
 //- !{@T defines/binding TVar}
 //- !{@T ref TVar}
-type Container2[T any] struct {
+type Pair[T any, U any] struct {
 	//- @T ref TVar2
 	//- !{@T defines/binding TVar}
 	//- !{@T ref TVar}
-	Element T
+	First T
+	//- @U ref UVar
+	Second U
 }
 
 // kythe/go/indexer/genericstruct_test.Container.T