go/ast: improve comment associations in empty function/loop/if bodies

Fixes golang#39753

Signed-off-by: Eva Charlotte Mayer <eva.mayer@tum.de>

Author: Eva Charlotte Mayer

src/go/ast/commentmap.go

@@ -204,6 +204,7 @@ func NewCommentMap(fset *token.FileSet, node Node, comments []*CommentGroup) Com
 				assoc = pg
 			case p != nil &&
 				(pend.Line == r.pos.Line ||
+					pend.Line-1 == r.pos.Line && r.end.Line+1 < qpos.Line ||
 					pend.Line+1 == r.pos.Line && r.end.Line+1 < qpos.Line ||
 					q == nil):
 				// same rules apply as above for p rather than pg,

src/go/ast/commentmap_test.go

@@ -61,6 +61,7 @@ func f1() {
 
 // f2
 func f2() {
+	// associated with f2.body
 }
 
 func f3() {
@@ -88,10 +89,11 @@ var res = map[string]string{
 	"29: *ast.FuncDecl":   "f1\nassociated with f1\nalso associated with f1\n",
 	"31: *ast.ExprStmt":   " associated with s1\nalso associated with s1\n",
 	"37: *ast.ExprStmt":   "associated with s2\nalso associated with s2\nline comment for s2\n",
+	"45: *ast.BlockStmt":  "associated with f2.body\n",
 	"45: *ast.FuncDecl":   "associated with f2\nf2\n",
-	"49: *ast.AssignStmt": "addition\n",
-	"49: *ast.BasicLit":   " 1\n",
-	"50: *ast.Ident":      "the very last comment\n",
+	"50: *ast.AssignStmt": "addition\n",
+	"50: *ast.BasicLit":   " 1\n",
+	"51: *ast.Ident":      "the very last comment\n",
 }
 
 func ctext(list []*CommentGroup) string {