From e6ea120e4bdf8813c95a91c87ab525bf1b5ec397 Mon Sep 17 00:00:00 2001
From: Jeroen Demeyer <jeroen.demeyer@be-mobile.com>
Date: Wed, 16 Mar 2022 13:32:30 +0100
Subject: [PATCH] Support Go 1.18 methods with type parameters

---
 go.mod                |  5 ++++-
 go.sum                | 11 +++++++++++
 gocov/convert.go      | 37 +++++++++++++++++++++++++------------
 gocov/convert_test.go | 40 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 80 insertions(+), 13 deletions(-)
 create mode 100644 gocov/convert_test.go

diff --git a/go.mod b/go.mod
index 1b4daf3..bd98ca7 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,7 @@ module github.com/axw/gocov
 
 go 1.12
 
-require golang.org/x/tools v0.0.0-20190617190820-da514acc4774
+require (
+	github.com/stretchr/testify v1.7.1
+	golang.org/x/tools v0.0.0-20190617190820-da514acc4774
+)
diff --git a/go.sum b/go.sum
index 967f84c..43c5cf6 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,10 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -5,3 +12,7 @@ golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/tools v0.0.0-20190617190820-da514acc4774 h1:CQVOmarCBFzTx0kbOU0ru54Cvot8SdSrNYjZPhQl+gk=
 golang.org/x/tools v0.0.0-20190617190820-da514acc4774/go.mod h1:/rFqwRUd4F7ZHNgwSSTFct+R/Kf4OFW1sUzUTQQTgfc=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/gocov/convert.go b/gocov/convert.go
index a5c2271..60955e9 100644
--- a/gocov/convert.go
+++ b/gocov/convert.go
@@ -189,6 +189,30 @@ type FuncVisitor struct {
 	funcs []*FuncExtent
 }
 
+func functionName(f *ast.FuncDecl) string {
+	name := f.Name.Name
+	if f.Recv == nil {
+		return name
+	} else {
+		// Function name is prepended with "T." if there is a receiver, where
+		// T is the type of the receiver, dereferenced if it is a pointer.
+		return exprName(f.Recv.List[0].Type) + "." + name
+	}
+}
+
+func exprName(x ast.Expr) string {
+	switch y := x.(type) {
+	case *ast.StarExpr:
+		return exprName(y.X)
+	case *ast.IndexExpr:
+		return fmt.Sprintf("%s[%s]", exprName(y.X), exprName(y.Index))
+	case *ast.Ident:
+		return y.Name
+	default:
+		return ""
+	}
+}
+
 // Visit implements the ast.Visitor interface.
 func (v *FuncVisitor) Visit(node ast.Node) ast.Visitor {
 	var body *ast.BlockStmt
@@ -198,18 +222,7 @@ func (v *FuncVisitor) Visit(node ast.Node) ast.Visitor {
 		body = n.Body
 	case *ast.FuncDecl:
 		body = n.Body
-		name = n.Name.Name
-		// Function name is prepended with "T." if there is a receiver, where
-		// T is the type of the receiver, dereferenced if it is a pointer.
-		if n.Recv != nil {
-			field := n.Recv.List[0]
-			switch recv := field.Type.(type) {
-			case *ast.StarExpr:
-				name = recv.X.(*ast.Ident).Name + "." + name
-			case *ast.Ident:
-				name = recv.Name + "." + name
-			}
-		}
+		name = functionName(n)
 	}
 	if body != nil {
 		start := v.fset.Position(node.Pos())
diff --git a/gocov/convert_test.go b/gocov/convert_test.go
new file mode 100644
index 0000000..0a96a4b
--- /dev/null
+++ b/gocov/convert_test.go
@@ -0,0 +1,40 @@
+package main
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExprName(t *testing.T) {
+	source := `
+package foo
+
+func Function() {}
+func (x Foo) Method() {}
+func (x *Foo) PtrMethod() {}
+func (x *Foo[T]) GenericMethod() {}
+`
+
+	fset := token.NewFileSet()
+	parsed, err := parser.ParseFile(fset, "", source, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	function0 := parsed.Decls[0].(*ast.FuncDecl)
+	assert.Equal(t, "Function", functionName(function0))
+
+	function1 := parsed.Decls[1].(*ast.FuncDecl)
+	assert.Equal(t, "Foo.Method", functionName(function1))
+
+	function2 := parsed.Decls[2].(*ast.FuncDecl)
+	assert.Equal(t, "Foo.PtrMethod", functionName(function2))
+
+	function3 := parsed.Decls[3].(*ast.FuncDecl)
+	assert.Equal(t, "Foo[T].GenericMethod", functionName(function3))
+
+}