go/doc: handle generic receiver strings

A receiver expression for a type with parameters may be an IndexExpr
or IndexListExpr in addition to an Ident or StarExpr. Add cases to
recvString to account for the new types.

Add tests that compare the fields of Func, and the fields of Type that
hold Funcs. These fields weren't previously tested.

Change-Id: Ia2cef51c85113422e0c5745c77dddcd53507ee51
Reviewed-on: https://go-review.googlesource.com/c/go/+/375095
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

2 files changed, 167 insertions, 2 deletions

diff --git a/src/go/doc/doc_test.go b/src/go/doc/doc_test.go
index c8cdf9eb37..5a5fbd8bf3 100644
--- a/src/go/doc/doc_test.go
+++ b/src/go/doc/doc_test.go
@@ -160,3 +160,142 @@ func TestAnchorID(t *testing.T) {
 		t.Errorf("anchorID(%q) = %q; want %q", in, got, want)
 	}
 }
+
+func TestFuncs(t *testing.T) {
+	fset := token.NewFileSet()
+	file, err := parser.ParseFile(fset, "funcs.go", strings.NewReader(funcsTestFile), parser.ParseComments)
+	if err != nil {
+		t.Fatal(err)
+	}
+	doc, err := NewFromFiles(fset, []*ast.File{file}, "importPath", Mode(0))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, f := range doc.Funcs {
+		f.Decl = nil
+	}
+	for _, ty := range doc.Types {
+		for _, f := range ty.Funcs {
+			f.Decl = nil
+		}
+		for _, m := range ty.Methods {
+			m.Decl = nil
+		}
+	}
+
+	compareFuncs := func(t *testing.T, msg string, got, want *Func) {
+		// ignore Decl and Examples
+		got.Decl = nil
+		got.Examples = nil
+		if !(got.Doc == want.Doc &&
+			got.Name == want.Name &&
+			got.Recv == want.Recv &&
+			got.Orig == want.Orig &&
+			got.Level == want.Level) {
+			t.Errorf("%s:\ngot  %+v\nwant %+v", msg, got, want)
+		}
+	}
+
+	compareSlices(t, "Funcs", doc.Funcs, funcsPackage.Funcs, compareFuncs)
+	compareSlices(t, "Types", doc.Types, funcsPackage.Types, func(t *testing.T, msg string, got, want *Type) {
+		if got.Name != want.Name {
+			t.Errorf("%s.Name: got %q, want %q", msg, got.Name, want.Name)
+		} else {
+			compareSlices(t, got.Name+".Funcs", got.Funcs, want.Funcs, compareFuncs)
+			compareSlices(t, got.Name+".Methods", got.Methods, want.Methods, compareFuncs)
+		}
+	})
+}
+
+func compareSlices[E any](t *testing.T, name string, got, want []E, compareElem func(*testing.T, string, E, E)) {
+	if len(got) != len(want) {
+		t.Errorf("%s: got %d, want %d", name, len(got), len(want))
+	}
+	for i := 0; i < len(got) && i < len(want); i++ {
+		compareElem(t, fmt.Sprintf("%s[%d]", name, i), got[i], want[i])
+	}
+}
+
+const funcsTestFile = `
+package funcs
+
+func F() {}
+
+type S1 struct {
+	S2  // embedded, exported
+	s3  // embedded, unexported
+}
+
+func NewS1()  S1 {return S1{} }
+func NewS1p() *S1 { return &S1{} }
+
+func (S1) M1() {}
+func (r S1) M2() {}
+func(S1) m3() {}		// unexported not shown
+func (*S1) P1() {}		// pointer receiver
+
+type S2 int
+func (S2) M3() {}		// shown on S2
+
+type s3 int
+func (s3) M4() {}		// shown on S1
+
+type G1[T any] struct {
+	*s3
+}
+
+func NewG1[T any]() G1[T] { return G1[T]{} }
+
+func (G1[T]) MG1() {}
+func (*G1[U]) MG2() {}
+
+type G2[T, U any] struct {}
+
+func NewG2[T, U any]() G2[T, U] { return G2[T, U]{} }
+
+func (G2[T, U]) MG3() {}
+func (*G2[A, B]) MG4() {}
+
+
+`
+
+var funcsPackage = &Package{
+	Funcs: []*Func{{Name: "F"}},
+	Types: []*Type{
+		{
+			Name:  "G1",
+			Funcs: []*Func{{Name: "NewG1"}},
+			Methods: []*Func{
+				{Name: "M4", Recv: "G1", // TODO: synthesize a param for G1?
+					Orig: "s3", Level: 1},
+				{Name: "MG1", Recv: "G1[T]", Orig: "G1[T]", Level: 0},
+				{Name: "MG2", Recv: "*G1[U]", Orig: "*G1[U]", Level: 0},
+			},
+		},
+		{
+			Name:  "G2",
+			Funcs: []*Func{{Name: "NewG2"}},
+			Methods: []*Func{
+				{Name: "MG3", Recv: "G2[T, U]", Orig: "G2[T, U]", Level: 0},
+				{Name: "MG4", Recv: "*G2[A, B]", Orig: "*G2[A, B]", Level: 0},
+			},
+		},
+		{
+			Name:  "S1",
+			Funcs: []*Func{{Name: "NewS1"}, {Name: "NewS1p"}},
+			Methods: []*Func{
+				{Name: "M1", Recv: "S1", Orig: "S1", Level: 0},
+				{Name: "M2", Recv: "S1", Orig: "S1", Level: 0},
+				{Name: "M4", Recv: "S1", Orig: "s3", Level: 1},
+				{Name: "P1", Recv: "*S1", Orig: "*S1", Level: 0},
+			},
+		},
+		{
+			Name: "S2",
+			Methods: []*Func{
+				{Name: "M3", Recv: "S2", Orig: "S2", Level: 0},
+			},
+		},
+	},
+}
diff --git a/src/go/doc/reader.go b/src/go/doc/reader.go
index 7ff868f062..de1d422106 100644
--- a/src/go/doc/reader.go
+++ b/src/go/doc/reader.go
@@ -5,11 +5,13 @@
 package doc
 
 import (
+	"fmt"
 	"go/ast"
 	"go/token"
 	"internal/lazyregexp"
 	"sort"
 	"strconv"
+	"strings"
 )
 
 // ----------------------------------------------------------------------------
@@ -22,8 +24,8 @@ import (
 //
 type methodSet map[string]*Func
 
-// recvString returns a string representation of recv of the
-// form "T", "*T", or "BADRECV" (if not a proper receiver type).
+// recvString returns a string representation of recv of the form "T", "*T",
+// "T[A, ...]", "*T[A, ...]" or "BADRECV" (if not a proper receiver type).
 //
 func recvString(recv ast.Expr) string {
 	switch t := recv.(type) {
@@ -31,10 +33,34 @@ func recvString(recv ast.Expr) string {
 		return t.Name
 	case *ast.StarExpr:
 		return "*" + recvString(t.X)
+	case *ast.IndexExpr:
+		// Generic type with one parameter.
+		return fmt.Sprintf("%s[%s]", recvString(t.X), recvParam(t.Index))
+	case *ast.IndexListExpr:
+		// Generic type with multiple parameters.
+		if len(t.Indices) > 0 {
+			var b strings.Builder
+			b.WriteString(recvString(t.X))
+			b.WriteByte('[')
+			b.WriteString(recvParam(t.Indices[0]))
+			for _, e := range t.Indices[1:] {
+				b.WriteString(", ")
+				b.WriteString(recvParam(e))
+			}
+			b.WriteByte(']')
+			return b.String()
+		}
 	}
 	return "BADRECV"
 }
 
+func recvParam(p ast.Expr) string {
+	if id, ok := p.(*ast.Ident); ok {
+		return id.Name
+	}
+	return "BADPARAM"
+}
+
 // set creates the corresponding Func for f and adds it to mset.
 // If there are multiple f's with the same name, set keeps the first
 // one with documentation; conflicts are ignored. The boolean