gopls/internal/golang: splitlines: s/parameter/arguments/ in CallExpr

(Another terminological nitpick that I missed until reading the docs.)

Also, commentary.

Change-Id: I8d985234637224be7b921bdaa8113baa9c54be66
Reviewed-on: https://go-review.googlesource.com/c/tools/+/595118
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>

gopls/internal/golang/lines.go

@@ -167,26 +167,21 @@ func findSplitJoinTarget(fset *token.FileSet, file *ast.File, src []byte, start,
 		for _, node := range path {
 			switch node := node.(type) {
 			case *ast.FuncType:
-				// target function signature parameters and results.
-				//   type someFunc func (a int, b int, c int) (d int, e int)
-				params := node.Params
-				if isCursorInside(params.Opening, params.Closing) {
-					return "parameters", params, params.Opening, params.Closing
+				// params or results of func signature
+				// Note:
+				// - each ast.Field (e.g. "x, y, z int") is considered a single item.
+				// - splitting Params and Results lists is not usually good style.
+				if p := node.Params; isCursorInside(p.Opening, p.Closing) {
+					return "parameters", p, p.Opening, p.Closing
 				}
-
-				results := node.Results
-				if results != nil && isCursorInside(results.Opening, results.Closing) {
-					return "results", results, results.Opening, results.Closing
+				if r := node.Results; r != nil && isCursorInside(r.Opening, r.Closing) {
+					return "results", r, r.Opening, r.Closing
 				}
-			case *ast.CallExpr:
-				// target function calls.
-				//   someFunction(a, b, c)
+			case *ast.CallExpr: // f(a, b, c)
 				if isCursorInside(node.Lparen, node.Rparen) {
-					return "parameters", node, node.Lparen, node.Rparen
+					return "arguments", node, node.Lparen, node.Rparen
 				}
-			case *ast.CompositeLit:
-				// target composite lit instantiation (structs, maps, arrays).
-				//   A{b: 1, c: 2, d: 3}
+			case *ast.CompositeLit: // T{a, b, c}
 				if isCursorInside(node.Lbrace, node.Rbrace) {
 					return "elements", node, node.Lbrace, node.Rbrace
 				}

gopls/internal/test/marker/testdata/codeaction/grouplines.txt

@@ -108,7 +108,7 @@ func a() {
         2,
         3,
         fmt.Sprintf(
-            "hello %d" /*@codeaction("hello", "hello", "refactor.rewrite", indent, "Join parameters into one line")*/,
+            "hello %d" /*@codeaction("hello", "hello", "refactor.rewrite", indent, "Join arguments into one line")*/,
             4,
         ))
 }
@@ -123,7 +123,7 @@ func a() {
         1,
         2,
         3,
-        fmt.Sprintf("hello %d" /*@codeaction("hello", "hello", "refactor.rewrite", indent, "Join parameters into one line")*/, 4))
+        fmt.Sprintf("hello %d" /*@codeaction("hello", "hello", "refactor.rewrite", indent, "Join arguments into one line")*/, 4))
 }
 
 -- structelts/structelts.go --

gopls/internal/test/marker/testdata/codeaction/splitlines.txt

@@ -103,7 +103,7 @@ package indent
 import "fmt"
 
 func a() {
-	fmt.Println(1, 2, 3, fmt.Sprintf("hello %d", 4)) //@codeaction("hello", "hello", "refactor.rewrite", indent, "Split parameters into separate lines")
+	fmt.Println(1, 2, 3, fmt.Sprintf("hello %d", 4)) //@codeaction("hello", "hello", "refactor.rewrite", indent, "Split arguments into separate lines")
 }
 
 -- @indent/indent/indent.go --
@@ -115,7 +115,7 @@ func a() {
 	fmt.Println(1, 2, 3, fmt.Sprintf(
 		"hello %d",
 		4,
-	)) //@codeaction("hello", "hello", "refactor.rewrite", indent, "Split parameters into separate lines")
+	)) //@codeaction("hello", "hello", "refactor.rewrite", indent, "Split arguments into separate lines")
 }
 
 -- indent2/indent2.go --
@@ -125,7 +125,7 @@ import "fmt"
 
 func a() {
 	fmt.
-		Println(1, 2, 3, fmt.Sprintf("hello %d", 4)) //@codeaction("1", "1", "refactor.rewrite", indent2, "Split parameters into separate lines")
+		Println(1, 2, 3, fmt.Sprintf("hello %d", 4)) //@codeaction("1", "1", "refactor.rewrite", indent2, "Split arguments into separate lines")
 }
 
 -- @indent2/indent2/indent2.go --
@@ -140,7 +140,7 @@ func a() {
 			2,
 			3,
 			fmt.Sprintf("hello %d", 4),
-		) //@codeaction("1", "1", "refactor.rewrite", indent2, "Split parameters into separate lines")
+		) //@codeaction("1", "1", "refactor.rewrite", indent2, "Split arguments into separate lines")
 }
 
 -- structelts/structelts.go --