gopls/internal/golang: fix folding range for function calls

gopls/internal/golang/folding_range.go

@@ -89,8 +89,13 @@ func foldingRangeFunc(pgf *parsego.File, n ast.Node, lineFoldingOnly bool) *Fold
 		// Fold from position of ":" to end.
 		start, end = n.Colon+1, n.End()
 	case *ast.CallExpr:
-		// Fold from position of "(" to position of ")".
+		// Fold between positions of or lines between "(" and ")".
 		start, end = n.Lparen+1, n.Rparen
+		if len(n.Args) > 0 {
+			argsStart := n.Args[0].End()
+			argsEnd := n.Args[len(n.Args)-1].End()
+			start, end = validLineFoldingRange(pgf.Tok, n.Lparen, n.Rparen, argsStart, argsEnd, lineFoldingOnly)
+		}
 	case *ast.FieldList:
 		// Fold between positions of or lines between opening parenthesis/brace and closing parenthesis/brace.
 		var startList, endList token.Pos

gopls/internal/test/marker/testdata/foldingrange/a_lineonly.txt

@@ -15,6 +15,7 @@ package folding //@foldingrange(raw)
 import (
 	"fmt"
 	_ "log"
+	"sort"
 )
 
 import _ "os"
@@ -85,12 +86,46 @@ func bar() string {
 this string
 is not indented`
 }
+
+func _() {
+	slice := []int{1, 2, 3}
+	sort.Slice(slice, func(i, j int) bool {
+		a, b := slice[i], slice[j]
+		return a < b
+	})
+
+	sort.Slice(slice, func(i, j int) bool { return slice[i] < slice[j] })
+
+	sort.Slice(
+		slice,
+		func(i, j int) bool {
+			return slice[i] < slice[j]
+		},
+	)
+
+	fmt.Println(
+		1, 2, 3,
+		4,
+	)
+
+	fmt.Println(1, 2, 3,
+		4, 5, 6,
+		7, 8, 9,
+		10)
+}
+
+func _(
+	a int, b int,
+	c int,
+) {
+}
 -- @raw --
 package folding //@foldingrange(raw)
 
 import (<0 kind="imports">
 	"fmt"
-	_ "log"</0>
+	_ "log"
+	"sort"</0>
 )
 
 import _ "os"
@@ -161,3 +196,36 @@ func bar() string {<2 kind="">
 this string
 is not indented`</2></22>
 }
+
+func _() {<23 kind="">
+	slice := []int{1, 2, 3}
+	sort.Slice(slice, func(i, j int) bool {<24 kind="">
+		a, b := slice[i], slice[j]
+		return a < b</24>
+	})
+
+	sort.Slice(slice, func(i, j int) bool { return slice[i] < slice[j] })
+
+	sort.Slice(<25 kind="">
+		slice,
+		func(i, j int) bool {<26 kind="">
+			return slice[i] < slice[j]</26>
+		}</25>,
+	)
+
+	fmt.Println(<27 kind="">
+		1, 2, 3,
+		4</27>,
+	)
+
+	fmt.Println(1, 2, 3,
+		4, 5, 6,
+		7, 8, 9,
+		10)</23>
+}
+
+func _(<28 kind="">
+	a int, b int,
+	c int</28>,
+) {
+}