gopls/internal/lsp/source: improve method hover

This change causes (*pkg.T).F to be rendered as "(t *pkg.T) F",
in other words, using declaration syntax, with the receiver name,
if any (as it may be mentioned by the doc comment), instead
of go/types syntax (which is a "method expression").

Fixes golang/go#62190

Change-Id: I3966449e7141a28ba84e097b868a92a41c21df52
Reviewed-on: https://go-review.googlesource.com/c/tools/+/546735
Auto-Submit: Alan Donovan <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
Commit-Queue: Alan Donovan <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: adonovan

gopls/internal/lsp/source/hover.go

@@ -5,6 +5,7 @@
 package source
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
@@ -220,6 +221,8 @@ func hover(ctx context.Context, snapshot *cache.Snapshot, fh file.Handle, pp pro
 	//
 	// TODO(rfindley): this should use FormatVarType to get proper qualification
 	// of identifiers, and we should revisit the formatting of method set.
+	//
+	// TODO(adonovan): this logic belongs in objectString.
 	_, isTypeName := obj.(*types.TypeName)
 	_, isTypeParam := obj.Type().(*typeparams.TypeParam)
 	if isTypeName && !isTypeParam {
@@ -695,11 +698,50 @@ func inferredSignatureString(obj types.Object, qf types.Qualifier, inferred *typ
 // It handles adding more information to the object string.
 // If spec is non-nil, it may be used to format additional declaration
 // syntax, and file must be the token.File describing its positions.
+//
+// Precondition: obj is not a built-in function or method.
 func objectString(obj types.Object, qf types.Qualifier, declPos token.Pos, file *token.File, spec ast.Spec) string {
 	str := types.ObjectString(obj, qf)
 
 	switch obj := obj.(type) {
+	case *types.Func:
+		// We fork ObjectString to improve its rendering of methods:
+		// specifically, we show the receiver name,
+		// and replace the period in (T).f by a space (#62190).
+
+		sig := obj.Type().(*types.Signature)
+
+		var buf bytes.Buffer
+		buf.WriteString("func ")
+		if recv := sig.Recv(); recv != nil {
+			buf.WriteByte('(')
+			if _, ok := recv.Type().(*types.Interface); ok {
+				// gcimporter creates abstract methods of
+				// named interfaces using the interface type
+				// (not the named type) as the receiver.
+				// Don't print it in full.
+				buf.WriteString("interface")
+			} else {
+				// Show receiver name (go/types does not).
+				name := recv.Name()
+				if name != "" && name != "_" {
+					buf.WriteString(name)
+					buf.WriteString(" ")
+				}
+				types.WriteType(&buf, recv.Type(), qf)
+			}
+			buf.WriteByte(')')
+			buf.WriteByte(' ') // space (go/types uses a period)
+		} else if s := qf(obj.Pkg()); s != "" {
+			buf.WriteString(s)
+			buf.WriteString(".")
+		}
+		buf.WriteString(obj.Name())
+		types.WriteSignature(&buf, sig, qf)
+		str = buf.String()
+
 	case *types.Const:
+		// Show value of a constant.
 		var (
 			declaration = obj.Val().String() // default formatted declaration
 			comment     = ""                 // if non-empty, a clarifying comment

gopls/internal/test/marker/testdata/definition/embed.txt

@@ -27,7 +27,7 @@ type R struct {
 	Field2 int //@loc(RField2, "Field2")
 }
 
-func (_ R) Hey() {} //@loc(RHey, "Hey")
+func (r R) Hey() {} //@loc(RHey, "Hey")
 
 type H interface { //@loc(H, "H")
 	Goodbye() //@loc(HGoodbye, "Goodbye")
@@ -111,7 +111,7 @@ var _ = S1{ //@def("S1", S1),hover("S1", "S1", S1)
 
 -- @AHi --
 ```go
-func (a.A).Hi()
+func (a.A) Hi()
 ```
 
 [`(a.A).Hi` on pkg.go.dev](https://pkg.go.dev/mod.com/a#A.Hi)
@@ -126,7 +126,7 @@ field F int
 [`(b.Embed).F` on pkg.go.dev](https://pkg.go.dev/mod.com/b#Embed.F)
 -- @HGoodbye --
 ```go
-func (a.H).Goodbye()
+func (a.H) Goodbye()
 ```
 
 @loc(HGoodbye, "Goodbye")
@@ -135,7 +135,7 @@ func (a.H).Goodbye()
 [`(a.H).Goodbye` on pkg.go.dev](https://pkg.go.dev/mod.com/a#H.Goodbye)
 -- @IB --
 ```go
-func (a.I).B()
+func (a.I) B()
 ```
 
 @loc(IB, "B")
@@ -144,7 +144,7 @@ func (a.I).B()
 [`(a.I).B` on pkg.go.dev](https://pkg.go.dev/mod.com/a#I.B)
 -- @JHello --
 ```go
-func (a.J).Hello()
+func (a.J) Hello()
 ```
 
 @loc(JHello, "Hello")
@@ -153,7 +153,7 @@ func (a.J).Hello()
 [`(a.J).Hello` on pkg.go.dev](https://pkg.go.dev/mod.com/a#J.Hello)
 -- @M --
 ```go
-func (embed).M()
+func (embed) M()
 ```
 
 [`(b.Embed).M` on pkg.go.dev](https://pkg.go.dev/mod.com/b#Embed.M)
@@ -168,7 +168,7 @@ field Field2 int
 [`(a.R).Field2` on pkg.go.dev](https://pkg.go.dev/mod.com/a#R.Field2)
 -- @RHey --
 ```go
-func (a.R).Hey()
+func (r a.R) Hey()
 ```
 
 [`(a.R).Hey` on pkg.go.dev](https://pkg.go.dev/mod.com/a#R.Hey)

gopls/internal/test/marker/testdata/definition/misc.txt

@@ -188,7 +188,7 @@ type J interface {
 [`a.J` on pkg.go.dev](https://pkg.go.dev/mod.com#J)
 -- @hoverSum --
 ```go
-func (*Pos).Sum() int
+func (p *Pos) Sum() int
 ```
 
 [`(a.Pos).Sum` on pkg.go.dev](https://pkg.go.dev/mod.com#Pos.Sum)

gopls/internal/test/marker/testdata/hover/godef.txt

@@ -136,7 +136,7 @@ func (NextThing).another() string
 [`a.NextThing` on pkg.go.dev](https://pkg.go.dev/godef.test/a#NextThing)
 -- @eth --
 ```go
-func (Thing).Method(i int) string
+func (t Thing) Method(i int) string
 ```
 
 [`(a.Thing).Method` on pkg.go.dev](https://pkg.go.dev/godef.test/a#Thing.Method)
@@ -343,7 +343,7 @@ field str string
 nested string
 -- @openMethod --
 ```go
-func (interface).open() error
+func (interface) open() error
 ```
 
 open method comment

gopls/internal/test/marker/testdata/hover/linkable_generics.txt

@@ -97,7 +97,7 @@ TODO(rfindley): should it? We should probably link to the type.
 [`generic.GT` on pkg.go.dev](https://pkg.go.dev/mod.com/generic#GT)
 -- @M --
 ```go
-func (GT[P]).M(p P)
+func (GT[P]) M(p P)
 ```
 
 [`(generic.GT).M` on pkg.go.dev](https://pkg.go.dev/mod.com/generic#GT.M)

gopls/internal/test/marker/testdata/hover/std.txt

@@ -46,7 +46,7 @@ func _() {
 }
 -- @hoverLock --
 ```go
-func (*sync.Mutex).Lock()
+func (m *sync.Mutex) Lock()
 ```
 
 Lock locks m.
@@ -55,7 +55,7 @@ Lock locks m.
 [`(sync.Mutex).Lock` on pkg.go.dev](https://pkg.go.dev/sync#Mutex.Lock)
 -- @hoverName --
 ```go
-func (*types.object).Name() string
+func (obj *types.object) Name() string
 ```
 
 Name returns the object's (package-local, unqualified) name.