internal/lsp/source: use the object as the hover source for type params

Use the type name object as the signature source for type parametes, as
it it efficiently formatted as "type parameter <name> <constraint>".

Fixes golang/go#51116

Change-Id: I3042ff248402dae833e3197c6ac320c2bd103c07
Reviewed-on: https://go-review.googlesource.com/c/tools/+/385018
Trust: Robert Findley <[email protected]>
Run-TryBot: Robert Findley <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: findleyr

internal/lsp/source/hover.go

@@ -477,6 +477,13 @@ func objectString(obj types.Object, qf types.Qualifier, inferred *types.Signatur
 func FindHoverContext(ctx context.Context, s Snapshot, pkg Package, obj types.Object, pkgNode ast.Node, fullDecl ast.Decl) (*HoverContext, error) {
 	var info *HoverContext
 
+	// Type parameters get their signature from their declaration object.
+	if _, isTypeName := obj.(*types.TypeName); isTypeName {
+		if _, isTypeParam := obj.Type().(*typeparams.TypeParam); isTypeParam {
+			return &HoverContext{signatureSource: obj}, nil
+		}
+	}
+
 	// This is problematic for a number of reasons. We really need to have a more
 	// general mechanism to validate the coherency of AST with type information,
 	// but absent that we must do our best to ensure that we don't use fullNode
@@ -555,15 +562,15 @@ func FindHoverContext(ctx context.Context, s Snapshot, pkg Package, obj types.Ob
 				}
 			}
 
-			info, err = formatGenDecl(node, spec, fullPos, obj)
+			info, err = hoverGenDecl(node, spec, fullPos, obj)
 			if err != nil {
 				return nil, err
 			}
 		}
 	case *ast.TypeSpec:
 		if obj.Parent() == types.Universe {
 			if genDecl, ok := fullDecl.(*ast.GenDecl); ok {
-				info = formatTypeSpec(node, genDecl)
+				info = hoverTypeSpec(node, genDecl)
 			}
 		}
 	case *ast.FuncDecl:
@@ -620,24 +627,24 @@ func isFunctionParam(obj types.Object, node *ast.FuncDecl) bool {
 	return false
 }
 
-// formatGenDecl returns hover information an object declared via spec inside
+// hoverGenDecl returns hover information an object declared via spec inside
 // of the GenDecl node. obj is the type-checked object corresponding to the
 // declaration, but may have been type-checked using a different AST than the
 // given nodes; fullPos is the position of obj in node's AST.
-func formatGenDecl(node *ast.GenDecl, spec ast.Spec, fullPos token.Pos, obj types.Object) (*HoverContext, error) {
+func hoverGenDecl(node *ast.GenDecl, spec ast.Spec, fullPos token.Pos, obj types.Object) (*HoverContext, error) {
 	if spec == nil {
 		return nil, errors.Errorf("no spec for node %v at position %v", node, fullPos)
 	}
 
 	// If we have a field or method.
 	switch obj.(type) {
 	case *types.Var, *types.Const, *types.Func:
-		return formatVar(spec, fullPos, obj, node), nil
+		return hoverVar(spec, fullPos, obj, node), nil
 	}
 	// Handle types.
 	switch spec := spec.(type) {
 	case *ast.TypeSpec:
-		return formatTypeSpec(spec, node), nil
+		return hoverTypeSpec(spec, node), nil
 	case *ast.ValueSpec:
 		return &HoverContext{signatureSource: spec, Comment: spec.Doc}, nil
 	case *ast.ImportSpec:
@@ -646,7 +653,8 @@ func formatGenDecl(node *ast.GenDecl, spec ast.Spec, fullPos token.Pos, obj type
 	return nil, errors.Errorf("unable to format spec %v (%T)", spec, spec)
 }
 
-func formatTypeSpec(spec *ast.TypeSpec, decl *ast.GenDecl) *HoverContext {
+// TODO(rfindley): rename this function.
+func hoverTypeSpec(spec *ast.TypeSpec, decl *ast.GenDecl) *HoverContext {
 	comment := spec.Doc
 	if comment == nil && decl != nil {
 		comment = decl.Doc
@@ -660,7 +668,7 @@ func formatTypeSpec(spec *ast.TypeSpec, decl *ast.GenDecl) *HoverContext {
 	}
 }
 
-func formatVar(node ast.Spec, fullPos token.Pos, obj types.Object, decl *ast.GenDecl) *HoverContext {
+func hoverVar(node ast.Spec, fullPos token.Pos, obj types.Object, decl *ast.GenDecl) *HoverContext {
 	var fieldList *ast.FieldList
 	switch spec := node.(type) {
 	case *ast.TypeSpec:

internal/lsp/testdata/godef/hover_generics/hover.go

@@ -1,11 +1,15 @@
 package hover
 
-type value[T any] struct { //@mark(value, "value"),hoverdef("value", value)
+type value[T any] struct { //@mark(value, "value"),hoverdef("value", value),mark(valueTdecl, "T"),hoverdef("T",valueTdecl)
 	val T   //@mark(valueTparam, "T"),hoverdef("T", valueTparam)
 	Q   int //@mark(valueQfield, "Q"),hoverdef("Q", valueQfield)
 }
 
-type Value[T any] struct {
+type Value[T any] struct { //@mark(ValueTdecl, "T"),hoverdef("T",ValueTdecl)
 	val T   //@mark(ValueTparam, "T"),hoverdef("T", ValueTparam)
 	Q   int //@mark(ValueQfield, "Q"),hoverdef("Q", ValueQfield)
 }
+
+func F[P interface{ ~int | string }]() { //@mark(Pparam, "P"),hoverdef("P",Pparam)
+	var _ P //@mark(Pvar, "P"),hoverdef("P",Pvar)
+}

internal/lsp/testdata/godef/hover_generics/hover.go.golden

@@ -5,31 +5,41 @@ type value[T any] struct {
 	Q   int //@mark(valueQfield, "Q"),hoverdef("Q", valueQfield)
 }
 ```
--- valueTparam-hoverdef --
+-- ValueQfield-hoverdef --
 ```go
-type value[T any] struct {
-	val T   //@mark(valueTparam, "T"),hoverdef("T", valueTparam)
-	Q   int //@mark(valueQfield, "Q"),hoverdef("Q", valueQfield)
-}
+field Q int
+```
+
+[`(hover.Value).Q` on pkg.go.dev](https://pkg.go.dev/golang.org/x/tools/internal/lsp/godef/hover_generics?utm_source=gopls#Value.Q)
+
+\@mark\(ValueQfield, \"Q\"\),hoverdef\(\"Q\", ValueQfield\)
+-- ValueTdecl-hoverdef --
+```go
+type parameter T any
+```
+-- ValueTparam-hoverdef --
+```go
+type parameter T any
 ```
 -- valueQfield-hoverdef --
 ```go
 field Q int
 ```
 
 \@mark\(valueQfield, \"Q\"\),hoverdef\(\"Q\", valueQfield\)
--- ValueTparam-hoverdef --
+-- valueTdecl-hoverdef --
 ```go
-type Value[T any] struct {
-	val T   //@mark(ValueTparam, "T"),hoverdef("T", ValueTparam)
-	Q   int //@mark(ValueQfield, "Q"),hoverdef("Q", ValueQfield)
-}
+type parameter T any
 ```
--- ValueQfield-hoverdef --
+-- valueTparam-hoverdef --
 ```go
-field Q int
+type parameter T any
+```
+-- Pparam-hoverdef --
+```go
+type parameter P interface{~int|string}
+```
+-- Pvar-hoverdef --
+```go
+type parameter P interface{~int|string}
 ```
-
-[`(hover.Value).Q` on pkg.go.dev](https://pkg.go.dev/golang.org/x/tools/internal/lsp/godef/hover_generics?utm_source=gopls#Value.Q)
-
-\@mark\(ValueQfield, \"Q\"\),hoverdef\(\"Q\", ValueQfield\)

internal/lsp/testdata/godef/infer_generics/inferred.go.golden

@@ -1,20 +1,20 @@
 -- argInfer-hoverdef --
 ```go
-func app(s []int, e int) []int // func[S₁ interface{~[]E₂}, E₂ interface{}](s S₁, e E₂) S₁
+func app(s []int, e int) []int // func[S interface{~[]E}, E interface{}](s S, e E) S
 ```
 -- constrInf-hoverdef --
 ```go
 func app(s []int, e int) []int // func[S₁ interface{~[]E₂}, E₂ interface{}](s S₁, e E₂) S₁
 ```
 -- constrInfer-hoverdef --
 ```go
-func app(s []int, e int) []int // func[S₁ interface{~[]E₂}, E₂ interface{}](s S₁, e E₂) S₁
+func app(s []int, e int) []int // func[S interface{~[]E}, E interface{}](s S, e E) S
 ```
 -- instance-hoverdef --
 ```go
-func app(s []int, e int) []int // func[S₁ interface{~[]E₂}, E₂ interface{}](s S₁, e E₂) S₁
+func app(s []int, e int) []int // func[S interface{~[]E}, E interface{}](s S, e E) S
 ```
 -- partialInfer-hoverdef --
 ```go
-func app(s []int, e int) []int // func[S₁ interface{~[]E₂}, E₂ interface{}](s S₁, e E₂) S₁
+func app(s []int, e int) []int // func[S interface{~[]E}, E interface{}](s S, e E) S
 ```

internal/lsp/testdata/summary_go1.18.txt.golden

@@ -16,7 +16,7 @@ SemanticTokenCount = 3
 SuggestedFixCount = 61
 FunctionExtractionCount = 25
 MethodExtractionCount = 6
-DefinitionsCount = 104
+DefinitionsCount = 108
 TypeDefinitionsCount = 18
 HighlightsCount = 69
 ReferencesCount = 27