internal/lsp: produce "method" in place of "member" as per the spec

As per the current specification, the correct token name that represents methods is `method`. The current implementation does not produce the correct set of result and results in methods being incorrectly highlighted. Furthermore, the parameter names of interface methods are treated as `method` which is not true, so a fix has been applied to handle `ast.FuncType` being `parameter`.

Spec: https://microsoft.github.io/language-server-protocol/specifications/specification-3-16/#textDocument_semanticTokens

Change-Id: Id5d2fafe9f948a4a175ae19b4c94cca8f48a4b79
GitHub-Last-Rev: 9a3b65ca4dd3bb0542969c043a2042001c7fcb63
GitHub-Pull-Request: golang/tools#340
Reviewed-on: https://go-review.googlesource.com/c/tools/+/349449
Run-TryBot: Peter Weinberger <pjw@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Rebecca Stambler <rstambler@golang.org>
Trust: Peter Weinberger <pjw@google.com>
Reviewed-by: Peter Weinberger <pjw@google.com>

gopls/doc/semantictokens.md

@@ -16,7 +16,7 @@ don't make intuitive sense (although `async documentation` has a certain appeal)
 
 The 22 semantic tokens are `namespace`, `type`, `class`, `enum`, `interface`,
 		`struct`, `typeParameter`, `parameter`, `variable`, `property`, `enumMember`,
-		`event`, `function`, `member`, `macro`, `keyword`, `modifier`, `comment`,
+		`event`, `function`, `method`, `macro`, `keyword`, `modifier`, `comment`,
 		`string`, `number`, `regexp`, `operator`.
 
 The 10 modifiers are `declaration`, `definition`, `readonly`, `static`,
@@ -72,7 +72,7 @@ alias, it would be marked. Otherwise the last component of the import path is ma
 1. __`type`__ Objects of type ```types.TypeName``` are marked `type`.
 If they are also ```types.Basic```
 the modifier is `defaultLibrary`. (And in ```type B struct{C}```, ```B``` has modifier `definition`.)
-1. __`parameter`__ The formal arguments in ```ast.FuncDecl``` nodes are marked `parameter`.
+1. __`parameter`__ The formal arguments in ```ast.FuncDecl``` and ```ast.FuncType``` nodes are marked `parameter`.
 1. __`variable`__  Identifiers in the
 scope of ```const``` are modified with `readonly`. ```nil``` is usually a `variable` modified with both
 `readonly` and `defaultLibrary`. (```nil``` is a predefined identifier; the user can redefine it,
@@ -80,8 +80,8 @@ in which case it would just be a variable, or whatever.) Identifiers of type ```
 not surprisingly, marked `variable`. Identifiers being defined (node ```ast.GenDecl```) are modified
 by `definition` and, if appropriate, `readonly`. Receivers (in method declarations) are
 `variable`.
-1. __`member`__ Members are marked at their definition (```func (x foo) bar() {}```) or declaration
-in an ```interface```. Members are not marked where they are used.
+1. __`method`__ Methods are marked at their definition (```func (x foo) bar() {}```) or declaration
+in an ```interface```. Methods are not marked where they are used.
 In ```x.bar()```, ```x``` will be marked
 either as a `namespace` if it is a package name, or as a `variable` if it is an interface value,
 so distinguishing ```bar``` seemed superfluous.

internal/lsp/semantic.go

@@ -155,7 +155,7 @@ const (
 	tokInterface tokenType = "interface"
 	tokParameter tokenType = "parameter"
 	tokVariable  tokenType = "variable"
-	tokMember    tokenType = "member"
+	tokMethod    tokenType = "method"
 	tokFunction  tokenType = "function"
 	tokKeyword   tokenType = "keyword"
 	tokComment   tokenType = "comment"
@@ -598,7 +598,7 @@ func (e *encoded) unkIdent(x *ast.Ident) {
 			_, okit := e.stack[n-2].(*ast.InterfaceType)
 			_, okfl := e.stack[n-1].(*ast.FieldList)
 			if okit && okfl {
-				tok(tokMember, def)
+				tok(tokMethod, def)
 				return
 			}
 		}
@@ -645,7 +645,7 @@ func (e *encoded) definitionFor(x *ast.Ident) (tokenType, []string) {
 			if x.Name == "_" {
 				return "", nil // not really a variable
 			}
-			return "variable", mods
+			return tokVariable, mods
 		case *ast.GenDecl:
 			if isDeprecated(y.Doc) {
 				mods = append(mods, "deprecated")
@@ -661,7 +661,7 @@ func (e *encoded) definitionFor(x *ast.Ident) (tokenType, []string) {
 					mods = append(mods, "deprecated")
 				}
 				if y.Recv != nil {
-					return tokMember, mods
+					return tokMethod, mods
 				}
 				return tokFunction, mods
 			}
@@ -671,8 +671,10 @@ func (e *encoded) definitionFor(x *ast.Ident) (tokenType, []string) {
 			}
 			// if x < ... < FieldList < FuncType < FuncDecl, this is a param
 			return tokParameter, mods
+		case *ast.FuncType:
+			return tokParameter, mods
 		case *ast.InterfaceType:
-			return tokMember, mods
+			return tokMethod, mods
 		case *ast.TypeSpec:
 			// GenDecl/Typespec/FuncType/FieldList/Field/Ident
 			// (type A func(b uint64)) (err error)
@@ -878,7 +880,7 @@ var (
 	semanticTypes = [...]string{
 		"namespace", "type", "class", "enum", "interface",
 		"struct", "typeParameter", "parameter", "variable", "property", "enumMember",
-		"event", "function", "member", "macro", "keyword", "modifier", "comment",
+		"event", "function", "method", "macro", "keyword", "modifier", "comment",
 		"string", "number", "regexp", "operator",
 	}
 	semanticModifiers = [...]string{

internal/lsp/testdata/semantic/a.go.golden

@@ -31,12 +31,12 @@
 }
 /*⇒4,keyword,[]*/type /*⇒1,type,[definition]*/B /*⇒9,keyword,[]*/interface {
 	/*⇒1,type,[]*/A
-	/*⇒3,member,[definition]*/sad(/*⇒3,type,[defaultLibrary]*/int) /*⇒4,type,[defaultLibrary]*/bool
+	/*⇒3,method,[definition]*/sad(/*⇒3,type,[defaultLibrary]*/int) /*⇒4,type,[defaultLibrary]*/bool
 }
 
 /*⇒4,keyword,[]*/type /*⇒1,type,[definition]*/F /*⇒3,type,[defaultLibrary]*/int
 
-/*⇒4,keyword,[]*/func (/*⇒1,variable,[]*/a /*⇒1,operator,[]*/*/*⇒1,type,[]*/A) /*⇒1,member,[definition]*/f() /*⇒4,type,[defaultLibrary]*/bool {
+/*⇒4,keyword,[]*/func (/*⇒1,variable,[]*/a /*⇒1,operator,[]*/*/*⇒1,type,[]*/A) /*⇒1,method,[definition]*/f() /*⇒4,type,[defaultLibrary]*/bool {
 	/*⇒3,keyword,[]*/var /*⇒1,variable,[definition]*/z /*⇒6,type,[defaultLibrary]*/string
 	/*⇒1,variable,[definition]*/x /*⇒2,operator,[]*/:= /*⇒5,string,[]*/"foo"
 	/*⇒1,variable,[]*/a(/*⇒1,variable,[]*/x)

internal/lsp/testdata/semantic/b.go.golden

@@ -31,6 +31,6 @@
 /*⇒4,keyword,[]*/type /*⇒2,type,[definition]*/CC /*⇒6,keyword,[]*/struct {
 	/*⇒2,variable,[definition]*/AA /*⇒3,type,[defaultLibrary]*/int
 }
-/*⇒4,keyword,[]*/type /*⇒1,type,[definition]*/D /*⇒4,keyword,[]*/func(/*⇒2,variable,[definition]*/aa /*⇒2,type,[]*/AA) (/*⇒2,variable,[definition]*/BB /*⇒5,type,[]*/error)
+/*⇒4,keyword,[]*/type /*⇒1,type,[definition]*/D /*⇒4,keyword,[]*/func(/*⇒2,parameter,[definition]*/aa /*⇒2,type,[]*/AA) (/*⇒2,parameter,[definition]*/BB /*⇒5,type,[]*/error)
 /*⇒4,keyword,[]*/type /*⇒1,type,[definition]*/E /*⇒4,keyword,[]*/func(/*⇒2,type,[]*/AA) /*⇒2,type,[]*/BB