internal/lsp/source: filter candidates when type name required

Now when we expect a type name at the cursor, we omit non-type name
completion candidates. For example:

inch := 1
var foo in<> // don't offer "inch"

I also added expected type name detection for value specs:

// Expect a type name at <>
var foo <>

Fixes golang/go#32806.

Change-Id: I32477cb286d2050bac5ccc767f8a608124fa5acd
Reviewed-on: https://go-review.googlesource.com/c/tools/+/216400
Run-TryBot: Muir Manders <muir@mnd.rs>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

internal/lsp/source/completion.go

@@ -324,6 +324,15 @@ func (c *completer) found(cand candidate) {
 		return
 	}
 
+	// If we know we want a type name, don't offer non-type name
+	// candidates. However, do offer package names since they can
+	// contain type names, and do offer any candidate without a type
+	// since we aren't sure if it is a type name or not (i.e. unimported
+	// candidate).
+	if c.wantTypeName() && obj.Type() != nil && !isTypeName(obj) && !isPkgName(obj) {
+		return
+	}
+
 	if c.matchingCandidate(&cand, nil) {
 		cand.score *= highScore
 	} else if isTypeName(obj) {
@@ -856,7 +865,7 @@ func (c *completer) lexical() error {
 
 			// If obj's type is invalid, find the AST node that defines the lexical block
 			// containing the declaration of obj. Don't resolve types for packages.
-			if _, ok := obj.(*types.PkgName); !ok && !typeIsValid(obj.Type()) {
+			if !isPkgName(obj) && !typeIsValid(obj.Type()) {
 				// Match the scope to its ast.Node. If the scope is the package scope,
 				// use the *ast.File as the starting node.
 				var node ast.Node
@@ -1720,6 +1729,11 @@ Nodes:
 				wantComparable = c.pos == n.Pos()+token.Pos(len("map["))
 			}
 			break Nodes
+		case *ast.ValueSpec:
+			if n.Type != nil && n.Type.Pos() <= c.pos && c.pos <= n.Type.End() {
+				wantTypeName = true
+			}
+			break Nodes
 		default:
 			if breaksExpectedTypeInference(p) {
 				return typeNameInference{}

internal/lsp/source/util.go

@@ -415,6 +415,11 @@ func isUntyped(T types.Type) bool {
 	return false
 }
 
+func isPkgName(obj types.Object) bool {
+	_, ok := obj.(*types.PkgName)
+	return ok
+}
+
 // isSelector returns the enclosing *ast.SelectorExpr when pos is in the
 // selector.
 func enclosingSelector(path []ast.Node, pos token.Pos) *ast.SelectorExpr {

internal/lsp/testdata/lsp/primarymod/arraytype/array_type.go.in

@@ -9,14 +9,14 @@ func _() {
 		val string //@item(atVal, "val", "string", "var")
 	)
 
-	[] //@complete(" //", atVal, PackageFoo)
+	[] //@complete(" //", PackageFoo)
 
-	[]val //@complete(" //", atVal)
+	[]val //@complete(" //")
 
 	[]foo.StructFoo //@complete(" //", StructFoo)
 
 	[]foo.StructFoo(nil) //@complete("(", StructFoo)
-	
+
 	[]*foo.StructFoo //@complete(" //", StructFoo)
 
 	[...]foo.StructFoo //@complete(" //", StructFoo)
@@ -32,12 +32,12 @@ func _() {
 	var mark []myInt //@item(atMark, "mark", "[]myInt", "var")
 
 	var s []myInt //@item(atS, "s", "[]myInt", "var")
-	s = []m //@complete(" //", atMyInt, atMark)
-	s = [] //@complete(" //", atMyInt, atMark, atS, PackageFoo)
+	s = []m //@complete(" //", atMyInt)
+	s = [] //@complete(" //", atMyInt, PackageFoo)
 
 	var a [1]myInt
-	a = [1]m //@complete(" //", atMyInt, atMark)
+	a = [1]m //@complete(" //", atMyInt)
 
 	var ds [][]myInt
-	ds = [][]m //@complete(" //", atMyInt, atMark)
+	ds = [][]m //@complete(" //", atMyInt)
 }

internal/lsp/testdata/lsp/primarymod/bar/bar.go.in

@@ -10,13 +10,13 @@ func helper(i foo.IntFoo) {} //@item(helper, "helper", "func(i foo.IntFoo)", "fu
 
 func _() {
 	help //@complete("l", helper)
-	_ = foo.StructFoo{} //@complete("S", IntFoo, StructFoo, Foo)
+	_ = foo.StructFoo{} //@complete("S", IntFoo, StructFoo)
 }
 
 // Bar is a function.
 func Bar() { //@item(Bar, "Bar", "func()", "func", "Bar is a function.")
 	foo.Foo()        //@complete("F", Foo, IntFoo, StructFoo)
-	var _ foo.IntFoo //@complete("I", Foo, IntFoo, StructFoo)
+	var _ foo.IntFoo //@complete("I", IntFoo, StructFoo)
 	foo.()           //@complete("(", Foo, IntFoo, StructFoo)
 }
 

internal/lsp/testdata/lsp/primarymod/builtins/builtin_args.go

@@ -33,13 +33,12 @@ func _() {
 
 	cap() //@rank(")", builtinSlice, builtinMap),rank(")", builtinArray, builtinString),rank(")", builtinArrayPtr, builtinPtr),rank(")", builtinChan, builtinInt)
 
-	make()              //@rank(")", builtinMapType, int),rank(")", builtinChanType, int),rank(")", builtinSliceType, int),rank(")", builtinMapType, builtinMap)
+	make()              //@rank(")", builtinMapType, int),rank(")", builtinChanType, int),rank(")", builtinSliceType, int),rank(")", builtinMapType, int)
 	make(aSliceType, a) //@rank(")", builtinInt, builtinSlice)
 
-	var _ []int = make() //@rank(")", builtinSliceType, builtinSlice)
+	var _ []int = make() //@rank(")", builtinSliceType, builtinMapType)
 
 	type myStruct struct{}  //@item(builtinStructType, "myStruct", "struct{...}", "struct")
-	new()                   //@rank(")", builtinStructType, builtinInt)
 	var _ *myStruct = new() //@rank(")", builtinStructType, int)
 
 	for k := range a { //@rank(" {", builtinSlice, builtinInt),rank(" {", builtinString, builtinInt),rank(" {", builtinChan, builtinInt),rank(" {", builtinArray, builtinInt),rank(" {", builtinArrayPtr, builtinInt),rank(" {", builtinMap, builtinInt),

internal/lsp/testdata/lsp/primarymod/fieldlist/field_list.go

@@ -3,25 +3,25 @@ package fieldlist
 var myInt int   //@item(flVar, "myInt", "int", "var")
 type myType int //@item(flType, "myType", "int", "type")
 
-func (my) _()    {} //@complete(") _", flType, flVar)
-func (my my) _() {} //@complete(" my)"),complete(") _", flType, flVar)
+func (my) _()    {} //@complete(") _", flType)
+func (my my) _() {} //@complete(" my)"),complete(") _", flType)
 
-func (myType) _() {} //@complete(") {", flType, flVar)
+func (myType) _() {} //@complete(") {", flType)
 
-func (myType) _(my my) {} //@complete(" my)"),complete(") {", flType, flVar)
+func (myType) _(my my) {} //@complete(" my)"),complete(") {", flType)
 
-func (myType) _() my {} //@complete(" {", flType, flVar)
+func (myType) _() my {} //@complete(" {", flType)
 
-func (myType) _() (my my) {} //@complete(" my"),complete(") {", flType, flVar)
+func (myType) _() (my my) {} //@complete(" my"),complete(") {", flType)
 
 func _() {
 	var _ struct {
-		//@complete("", flType, flVar)
-		m my //@complete(" my"),complete(" //", flType, flVar)
+		//@complete("", flType)
+		m my //@complete(" my"),complete(" //", flType)
 	}
 
 	var _ interface {
-		//@complete("", flType, flVar)
-		m() my //@complete("("),complete(" //", flType, flVar)
+		//@complete("", flType)
+		m() my //@complete("("),complete(" //", flType)
 	}
 }

internal/lsp/testdata/lsp/primarymod/func_rank/func_rank.go.in

@@ -4,11 +4,11 @@ var stringAVar = "var"    //@item(stringAVar, "stringAVar", "string", "var")
 func stringBFunc() string { return "str" } //@item(stringBFunc, "stringBFunc", "func() string", "func")
 type stringer struct{}    //@item(stringer, "stringer", "struct{...}", "struct")
 
-func _() stringer //@complete("tr", stringer, stringAVar, stringBFunc)
+func _() stringer //@complete("tr", stringer)
 
-func _(val stringer) {} //@complete("tr", stringer, stringAVar, stringBFunc)
+func _(val stringer) {} //@complete("tr", stringer)
 
-func (stringer) _() {} //@complete("tr", stringer, stringAVar, stringBFunc)
+func (stringer) _() {} //@complete("tr", stringer)
 
 func _() {
 	var s struct {

internal/lsp/testdata/lsp/primarymod/maps/maps.go.in

@@ -11,8 +11,8 @@ func _() {
 	// comparable
 	type aStruct struct{} //@item(mapStructType, "aStruct", "struct{...}", "struct")
 
-	map[]a{} //@complete("]", mapSliceTypePtr, mapStructType, mapVar)
+	map[]a{} //@complete("]", mapSliceTypePtr, mapStructType)
 
-	map[a]a{} //@complete("]", mapSliceTypePtr, mapStructType, mapVar)
-	map[a]a{} //@complete("{", mapSliceType, mapStructType, mapVar)
+	map[a]a{} //@complete("]", mapSliceTypePtr, mapStructType)
+	map[a]a{} //@complete("{", mapSliceType, mapStructType)
 }

internal/lsp/testdata/lsp/primarymod/rank/type_assert_rank.go.in

@@ -4,5 +4,5 @@ func _() {
 	type flower int //@item(flower, "flower", "int", "type")
 	var fig string  //@item(fig, "fig", "string", "var")
 
-	_ = interface{}(nil).(f) //@complete(") //", flower, fig)
+	_ = interface{}(nil).(f) //@complete(") //", flower)
 }

internal/lsp/testdata/lsp/primarymod/rank/type_switch_rank.go.in

@@ -5,7 +5,7 @@ func _() {
 	var banana string //@item(banana, "banana", "string", "var")
 
 	switch interface{}(pear).(type) {
-	case b: //@complete(":", basket, banana)
+	case b: //@complete(":", basket)
 		b //@complete(" //", banana, basket)
 	}
 }

internal/lsp/testdata/lsp/primarymod/unresolved/unresolved.go.in

@@ -1,6 +1,6 @@
 package unresolved
 
-func foo(interface{}) { //@item(unresolvedFoo, "foo", "func(interface{})", "func")
+func foo(interface{}) {
 	// don't crash on fake "resolved" type
-	foo(func(i, j f //@complete(" //", unresolvedFoo)
+	foo(func(i, j f //@complete(" //")
 }

internal/lsp/testdata/lsp/summary.txt.golden

@@ -4,7 +4,7 @@ CompletionSnippetCount = 67
 UnimportedCompletionsCount = 11
 DeepCompletionsCount = 5
 FuzzyCompletionsCount = 8
-RankedCompletionsCount = 86
+RankedCompletionsCount = 85
 CaseSensitiveCompletionsCount = 4
 DiagnosticsCount = 38
 FoldingRangesCount = 2