go/doc: recognize methods on generic types as Funcs

When writing markdown for godoc, we can reference a method M of
a type T as [T.M]. This doesn't currently work for methods on generic
types because the declaration of the type parameter gets in the way.
(You'd have to write [T[P].M] and that doesn't parse, and even if it
did you'd have to spell "P" correctly.)

Get rid of the type parameter when building the list of Funcs so
[T.M] works in godoc if T is generic.

Change-Id: I8ef5264124a944967df3ce20ddd40a2447ff4187
Reviewed-on: https://go-review.googlesource.com/c/go/+/449236
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
Run-TryBot: Keith Randall <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: randall77

src/go/doc/comment_test.go

@@ -24,12 +24,12 @@ func TestComment(t *testing.T) {
 	pkg := New(pkgs["pkgdoc"], "testdata/pkgdoc", 0)
 
 	var (
-		input           = "[T] and [U] are types, and [T.M] is a method, but [V] is a broken link. [rand.Int] and [crand.Reader] are things.\n"
-		wantHTML        = `<p><a href="#T">T</a> and <a href="#U">U</a> are types, and <a href="#T.M">T.M</a> is a method, but [V] is a broken link. <a href="/math/rand#Int">rand.Int</a> and <a href="/crypto/rand#Reader">crand.Reader</a> are things.` + "\n"
-		wantOldHTML     = "<p>[T] and [U] are <i>types</i>, and [T.M] is a method, but [V] is a broken link. [rand.Int] and [crand.Reader] are things.\n"
-		wantMarkdown    = "[T](#T) and [U](#U) are types, and [T.M](#T.M) is a method, but \\[V] is a broken link. [rand.Int](/math/rand#Int) and [crand.Reader](/crypto/rand#Reader) are things.\n"
-		wantText        = "T and U are types, and T.M is a method, but [V] is a broken link. rand.Int and\ncrand.Reader are things.\n"
-		wantOldText     = "[T] and [U] are types, and [T.M] is a method, but [V] is a broken link.\n[rand.Int] and [crand.Reader] are things.\n"
+		input           = "[T] and [U] are types, and [T.M] is a method, but [V] is a broken link. [rand.Int] and [crand.Reader] are things. [G.M1] and [G.M2] are generic methods.\n"
+		wantHTML        = `<p><a href="#T">T</a> and <a href="#U">U</a> are types, and <a href="#T.M">T.M</a> is a method, but [V] is a broken link. <a href="/math/rand#Int">rand.Int</a> and <a href="/crypto/rand#Reader">crand.Reader</a> are things. <a href="#G.M1">G.M1</a> and <a href="#G.M2">G.M2</a> are generic methods.` + "\n"
+		wantOldHTML     = "<p>[T] and [U] are <i>types</i>, and [T.M] is a method, but [V] is a broken link. [rand.Int] and [crand.Reader] are things. [G.M1] and [G.M2] are generic methods.\n"
+		wantMarkdown    = "[T](#T) and [U](#U) are types, and [T.M](#T.M) is a method, but \\[V] is a broken link. [rand.Int](/math/rand#Int) and [crand.Reader](/crypto/rand#Reader) are things. [G.M1](#G.M1) and [G.M2](#G.M2) are generic methods.\n"
+		wantText        = "T and U are types, and T.M is a method, but [V] is a broken link. rand.Int and\ncrand.Reader are things. G.M1 and G.M2 are generic methods.\n"
+		wantOldText     = "[T] and [U] are types, and [T.M] is a method, but [V] is a broken link.\n[rand.Int] and [crand.Reader] are things. [G.M1] and [G.M2] are generic methods.\n"
 		wantSynopsis    = "T and U are types, and T.M is a method, but [V] is a broken link."
 		wantOldSynopsis = "[T] and [U] are types, and [T.M] is a method, but [V] is a broken link."
 	)

src/go/doc/doc.go

@@ -76,7 +76,7 @@ type Func struct {
 
 	// methods
 	// (for functions, these fields have the respective zero value)
-	Recv  string // actual   receiver "T" or "*T"
+	Recv  string // actual   receiver "T" or "*T" possibly followed by type parameters [P1, ..., Pn]
 	Orig  string // original receiver "T" or "*T"
 	Level int    // embedding level; 0 means not embedded
 
@@ -173,7 +173,11 @@ func (p *Package) collectTypes(types []*Type) {
 func (p *Package) collectFuncs(funcs []*Func) {
 	for _, f := range funcs {
 		if f.Recv != "" {
-			p.syms[strings.TrimPrefix(f.Recv, "*")+"."+f.Name] = true
+			r := strings.TrimPrefix(f.Recv, "*")
+			if i := strings.IndexByte(r, '['); i >= 0 {
+				r = r[:i] // remove type parameters
+			}
+			p.syms[r+"."+f.Name] = true
 		} else {
 			p.syms[f.Name] = true
 		}

src/go/doc/testdata/pkgdoc/doc.go

@@ -17,3 +17,8 @@ func (T) M() {}
 
 var _ = rand.Int
 var _ = crand.Reader
+
+type G[T any] struct{ x T }
+
+func (g G[T]) M1() {}
+func (g *G[T]) M2() {}