internal/lsp: skip return highlighting if cursor is in arglist of func

If the cursor is within an argument that is within a callExpr which is
in a return statement, we only want it to highlight the ident that the cursor
is in. We do not want it to highlight the entire function.

Updates golang/go#34496

Change-Id: If4025660a99fd5df90098e0560a5e9e7260e33c8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/211338
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rohan Challa <rohan@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/lsp/source/highlight.go

@@ -60,11 +60,20 @@ func highlightFuncControlFlow(ctx context.Context, snapshot Snapshot, m *protoco
 	inReturnList := false
 Outer:
 	// Reverse walk the path till we get to the func block.
-	for _, n := range path {
+	for i, n := range path {
 		switch node := n.(type) {
 		case *ast.KeyValueExpr:
 			// If cursor is in a key: value expr, we don't want control flow highlighting
 			return nil, nil
+		case *ast.CallExpr:
+			// If cusor is an arg in a callExpr, we don't want control flow highlighting.
+			if i > 0 {
+				for _, arg := range node.Args {
+					if arg == path[i-1] {
+						return nil, nil
+					}
+				}
+			}
 		case *ast.Field:
 			inReturnList = true
 		case *ast.FuncLit:

internal/lsp/testdata/highlights/highlights.go

@@ -101,3 +101,8 @@ func testReturnMultipleFields() (float32, string) { //@mark(retVal31, "float32")
 	}
 	return 4.9, "test" //@mark(retVal51, "4.9"),mark(retVal52, "\"test\""),highlight(retVal51, retVal31, retVal41, retVal51),highlight(retVal52, retVal32, retVal42, retVal52)
 }
+
+func testReturnFunc() int32 { //@mark(retCall, "int32")
+	mulch := 1          //@mark(mulchDec, "mulch"),highlight(mulchDec, mulchDec, mulchRet)
+	return int32(mulch) //@mark(mulchRet, "mulch"),mark(retFunc, "int32"),mark(retTotal, "int32(mulch)"),highlight(mulchRet, mulchDec, mulchRet),highlight(retFunc, retCall, retFunc, retTotal)
+}

internal/lsp/testdata/summary.txt.golden

@@ -13,7 +13,7 @@ ImportCount = 7
 SuggestedFixCount = 1
 DefinitionsCount = 39
 TypeDefinitionsCount = 2
-HighlightsCount = 41
+HighlightsCount = 44
 ReferencesCount = 7
 RenamesCount = 22
 PrepareRenamesCount = 8