cmd/guru: add type position to describe command

Add typepos field to json output of describe command. This field shows where
type of current (under cursor) identifier is defined. This will help code editors
implement command 'Go to type definition'.

Implements [#27308](https://github.com/golang/go/issues/27308)

Change-Id: I4e02ddbdc03fecec98135b8996f9562a88a9cfb8
GitHub-Last-Rev: be47e397a293a96d3d39776d6090d861e7904a24
GitHub-Pull-Request: golang/tools#50
Reviewed-on: https://go-review.googlesource.com/c/140379
Reviewed-by: Alan Donovan <adonovan@google.com>

cmd/guru/describe.go

@@ -340,6 +340,7 @@ func describeValue(qpos *queryPos, path []ast.Node) (*describeValueResult, error
 		qpos:     qpos,
 		expr:     expr,
 		typ:      typ,
+		names:    appendNames(nil, typ),
 		constVal: constVal,
 		obj:      obj,
 		methods:  accessibleMethods(typ, qpos.info.Pkg),
@@ -347,10 +348,34 @@ func describeValue(qpos *queryPos, path []ast.Node) (*describeValueResult, error
 	}, nil
 }
 
+// appendNames returns named types found within the Type by
+// removing map, pointer, channel, slice, and array constructors.
+// It does not descend into structs or interfaces.
+func appendNames(names []*types.Named, typ types.Type) []*types.Named {
+	// elemType specifies type that has some element in it
+	// such as array, slice, chan, pointer
+	type elemType interface {
+		Elem() types.Type
+	}
+
+	switch t := typ.(type) {
+	case *types.Named:
+		names = append(names, t)
+	case *types.Map:
+		names = appendNames(names, t.Key())
+		names = appendNames(names, t.Elem())
+	case elemType:
+		names = appendNames(names, t.Elem())
+	}
+
+	return names
+}
+
 type describeValueResult struct {
 	qpos     *queryPos
 	expr     ast.Expr       // query node
 	typ      types.Type     // type of expression
+	names    []*types.Named // named types within typ
 	constVal constant.Value // value of expression, if constant
 	obj      types.Object   // var/func/const object, if expr was Ident
 	methods  []*types.Selection
@@ -398,6 +423,7 @@ func (r *describeValueResult) PrintPlain(printf printfFunc) {
 
 	printMethods(printf, r.expr, r.methods)
 	printFields(printf, r.expr, r.fields)
+	printNamedTypes(printf, r.expr, r.names)
 }
 
 func (r *describeValueResult) JSON(fset *token.FileSet) []byte {
@@ -409,14 +435,23 @@ func (r *describeValueResult) JSON(fset *token.FileSet) []byte {
 		objpos = fset.Position(r.obj.Pos()).String()
 	}
 
+	typesPos := make([]serial.Definition, len(r.names))
+	for i, t := range r.names {
+		typesPos[i] = serial.Definition{
+			ObjPos: fset.Position(t.Obj().Pos()).String(),
+			Desc:   r.qpos.typeString(t),
+		}
+	}
+
 	return toJSON(&serial.Describe{
 		Desc:   astutil.NodeDescription(r.expr),
 		Pos:    fset.Position(r.expr.Pos()).String(),
 		Detail: "value",
 		Value: &serial.DescribeValue{
-			Type:   r.qpos.typeString(r.typ),
+			Type:     r.qpos.typeString(r.typ),
-			Value:  value,
+			TypesPos: typesPos,
-			ObjPos: objpos,
+			Value:    value,
+			ObjPos:   objpos,
 		},
 	})
 }
@@ -524,6 +559,19 @@ func printFields(printf printfFunc, node ast.Node, fields []describeField) {
 	}
 }
 
+func printNamedTypes(printf printfFunc, node ast.Node, names []*types.Named) {
+	if len(names) > 0 {
+		printf(node, "Named types:")
+	}
+
+	for _, t := range names {
+		// Print the type relative to the package
+		// in which it was defined, not the query package,
+		printf(t.Obj(), "\ttype %s defined here",
+			types.TypeString(t.Obj().Type(), types.RelativeTo(t.Obj().Pkg())))
+	}
+}
+
 func (r *describeTypeResult) PrintPlain(printf printfFunc) {
 	printf(r.node, "%s", r.description)
 

cmd/guru/serial/serial.go

@@ -193,9 +193,10 @@ type PointsTo struct {
 // A DescribeValue is the additional result of a 'describe' query
 // if the selection indicates a value or expression.
 type DescribeValue struct {
-	Type   string `json:"type"`             // type of the expression
+	Type     string       `json:"type"`               // type of the expression
-	Value  string `json:"value,omitempty"`  // value of the expression, if constant
+	Value    string       `json:"value,omitempty"`    // value of the expression, if constant
-	ObjPos string `json:"objpos,omitempty"` // location of the definition, if an Ident
+	ObjPos   string       `json:"objpos,omitempty"`   // location of the definition, if an Ident
+	TypesPos []Definition `json:"typespos,omitempty"` // location of the named types, that type consist of
 }
 
 type DescribeMethod struct {

cmd/guru/testdata/src/describe-json/main.go

@@ -25,5 +25,5 @@ type I interface {
 type C int // @describe desc-type-C "C"
 type D struct{}
 
-func (c C) f()  {}
+func (c C) f()  {} // @describe desc-param-c "\\bc\\b"
-func (d *D) f() {}
+func (d *D) f() {} // @describe desc-param-d "\\bd\\b"

cmd/guru/testdata/src/describe-json/main.golden

@@ -68,7 +68,13 @@
 	"detail": "value",
 	"value": {
 		"type": "I",
-		"objpos": "testdata/src/describe-json/main.go:12:6"
+		"objpos": "testdata/src/describe-json/main.go:12:6",
+		"typespos": [
+			{
+				"objpos": "testdata/src/describe-json/main.go:21:6",
+				"desc": "I"
+			}
+		]
 	}
 }
 -------- @describe desc-stmt --------
@@ -94,3 +100,35 @@
 		]
 	}
 }
+-------- @describe desc-param-c --------
+{
+	"desc": "identifier",
+	"pos": "testdata/src/describe-json/main.go:28:7",
+	"detail": "value",
+	"value": {
+		"type": "C",
+		"objpos": "testdata/src/describe-json/main.go:28:7",
+		"typespos": [
+			{
+				"objpos": "testdata/src/describe-json/main.go:25:6",
+				"desc": "C"
+			}
+		]
+	}
+}
+-------- @describe desc-param-d --------
+{
+	"desc": "identifier",
+	"pos": "testdata/src/describe-json/main.go:29:7",
+	"detail": "value",
+	"value": {
+		"type": "*D",
+		"objpos": "testdata/src/describe-json/main.go:29:7",
+		"typespos": [
+			{
+				"objpos": "testdata/src/describe-json/main.go:26:6",
+				"desc": "D"
+			}
+		]
+	}
+}

cmd/guru/testdata/src/describe/main.go

@@ -23,14 +23,15 @@ var global = new(string) // NB: ssa.Global is indirect, i.e. **string
 
 func main() { // @describe func-def-main "main"
 	// func objects
-	_ = main   // @describe func-ref-main "main"
+	_ = main      // @describe func-ref-main "main"
-	_ = (*C).f // @describe func-ref-*C.f "..C..f"
+	_ = (*C).f    // @describe func-ref-*C.f "..C..f"
-	_ = D.f    // @describe func-ref-D.f "D.f"
+	_ = D.f       // @describe func-ref-D.f "D.f"
-	_ = I.f    // @describe func-ref-I.f "I.f"
+	_ = I.f       // @describe func-ref-I.f "I.f"
-	var d D    // @describe type-D "D"
+	var d D       // @describe type-D "D"
-	var i I    // @describe type-I "I"
+	var i I       // @describe type-I "I"
-	_ = d.f    // @describe func-ref-d.f "d.f"
+	_ = d.f       // @describe func-ref-d.f "d.f"
-	_ = i.f    // @describe func-ref-i.f "i.f"
+	_ = i.f       // @describe func-ref-i.f "i.f"
+	var slice []D // @describe slice-of-D "slice"
 
 	var dptr *D // @describe ptr-with-nonptr-methods "dptr"
 	_ = dptr
@@ -85,6 +86,11 @@ func main() { // @describe func-def-main "main"
 
 	var _ lib.Outer // @describe lib-outer "Outer"
 
+	var mmm map[C]D // @describe var-map-of-C-D "mmm"
+
+	d := newD().ThirdField // @describe field-access "ThirdField"
+
+	astCopy := ast
 	unknown() // @describe call-unknown "\\("
 }
 
@@ -96,7 +102,10 @@ type C int
 type D struct {
 	Field        int
 	AnotherField string
+	ThirdField   C
 }
 
 func (c *C) f() {}
 func (d D) f()  {}
+
+func newD() D { return D{} }

cmd/guru/testdata/src/describe/main.golden

@@ -10,6 +10,7 @@ definition of package "describe"
 	type  cake   float64
 	var   global *string
 	func  main   func()
+	func  newD   func() D
 	const pi     untyped float = 3.141
 	const pie    cake = 3.141
 
@@ -31,6 +32,8 @@ definition of const pi untyped float of value 3.141
 
 -------- @describe const-def-pie --------
 definition of const pie cake of value 3.141
+Named types:
+	type cake defined here
 
 -------- @describe const-ref-pi --------
 reference to const pi untyped float of value 3.141
@@ -56,13 +59,14 @@ reference to interface method func (I).f()
 defined here
 
 -------- @describe type-D --------
-reference to type D (size 24, align 8)
+reference to type D (size 32, align 8)
-defined as struct{Field int; AnotherField string}
+defined as struct{Field int; AnotherField string; ThirdField C}
 Methods:
 	method (D) f()
 Fields:
 	Field        int
 	AnotherField string
+	ThirdField   C
 
 -------- @describe type-I --------
 reference to type I (size 16, align 8)
@@ -78,6 +82,11 @@ defined here
 reference to interface method func (I).f()
 defined here
 
+-------- @describe slice-of-D --------
+definition of var slice []D
+Named types:
+	type D defined here
+
 -------- @describe ptr-with-nonptr-methods --------
 definition of var dptr *D
 Methods:
@@ -85,6 +94,9 @@ Methods:
 Fields:
 	Field        int
 	AnotherField string
+	ThirdField   C
+Named types:
+	type D defined here
 
 -------- @describe ref-lexical-d --------
 reference to var d D
@@ -94,6 +106,9 @@ Methods:
 Fields:
 	Field        int
 	AnotherField string
+	ThirdField   C
+Named types:
+	type D defined here
 
 -------- @describe ref-anon --------
 reference to var anon func()
@@ -123,24 +138,32 @@ reference to var i I
 defined here
 Methods:
 	method (I) f()
+Named types:
+	type I defined here
 
 -------- @describe var-ref-i-D --------
 reference to var i I
 defined here
 Methods:
 	method (I) f()
+Named types:
+	type I defined here
 
 -------- @describe var-ref-i --------
 reference to var i I
 defined here
 Methods:
 	method (I) f()
+Named types:
+	type I defined here
 
 -------- @describe const-local-pi --------
 definition of const localpi untyped float of value 3.141
 
 -------- @describe const-local-pie --------
 definition of const localpie cake of value 3.141
+Named types:
+	type cake defined here
 
 -------- @describe const-ref-localpi --------
 reference to const localpi untyped float of value 3.141
@@ -199,6 +222,20 @@ Fields:
 	inner.C           bool
 	inner.recursive.E bool
 
+-------- @describe var-map-of-C-D --------
+definition of var mmm map[C]D
+Named types:
+	type C defined here
+	type D defined here
+
+-------- @describe field-access --------
+reference to field ThirdField C
+defined here
+Methods:
+	method (*C) f()
+Named types:
+	type C defined here
+
 -------- @describe call-unknown --------
 function call of type invalid type
 

cmd/guru/testdata/src/referrers-json/main.golden

@@ -43,7 +43,7 @@
 	"package": "describe",
 	"refs": [
 		{
-			"pos": "testdata/src/describe/main.go:86:8",
+			"pos": "testdata/src/describe/main.go:87:8",
 			"text": "\tvar _ lib.Outer // @describe lib-outer \"Outer\""
 		}
 	]