Fix hover documentation for intersected properties

internal/fourslash/tests/hoverIntersectionPropertyDocumentation_test.go

@@ -0,0 +1,34 @@
+package fourslash_test
+
+import (
+	"testing"
+
+	"github.com/microsoft/typescript-go/internal/fourslash"
+	"github.com/microsoft/typescript-go/internal/testutil"
+)
+
+func TestHoverIntersectionPropertyDocumentation(t *testing.T) {
+	t.Parallel()
+	defer testutil.RecoverAndFail(t, "Panic on fourslash test")
+
+	const content = `
+interface A {
+    /** interface A */
+    prop: () => number;
+}
+
+interface B {
+    /** interface B */
+    prop: () => number;
+}
+
+type C = A & B;
+declare const c: C;
+
+c./*1*/prop;
+`
+	f, done := fourslash.NewFourslash(t, nil /*capabilities*/, content)
+	defer done()
+
+	f.VerifyQuickInfoAt(t, "1", "(property) prop: () => number", "interface A\ninterface B")
+}

internal/ls/hover.go

@@ -101,6 +101,13 @@ func (l *LanguageService) getQuickInfoAndDocumentationForSymbol(c *checker.Check
 	if documentation != "" {
 		return quickInfo, documentation
 	}
+	// Synthetic union and intersection properties can have declarations without a value declaration.
+	if info.declaration == nil && symbol != nil {
+		documentation = l.getDocumentationFromDeclarations(c, symbol, symbol.Declarations, node, contentFormat, false /*commentOnly*/)
+		if documentation != "" {
+			return quickInfo, documentation
+		}
+	}
 
 	return quickInfo, l.documentationFromAlias(c, symbol, node, contentFormat)
 }

internal/ls/jsdoc.go

@@ -28,16 +28,25 @@ func (l *LanguageService) GetSymbolDocumentationComment(c *checker.Checker, symb
 	if symbol == nil {
 		return ""
 	}
+	return l.getDocumentationFromDeclarations(c, symbol, symbol.Declarations, nil, lsproto.MarkupKindPlainText, true /*commentOnly*/)
+}
+
+// getDocumentationFromDeclarations gathers and deduplicates documentation from a set of declarations.
+func (l *LanguageService) getDocumentationFromDeclarations(c *checker.Checker, symbol *ast.Symbol, declarations []*ast.Node, location *ast.Node, contentFormat lsproto.MarkupKind, commentOnly bool) string {
 	var parts []string
 	var seen collections.Set[*ast.Node]
-	for _, decl := range symbol.Declarations {
+	for _, decl := range declarations {
 		if decl == nil {
 			continue
 		}
 		if !seen.AddIfAbsent(decl) {
 			continue
 		}
-		if doc := l.getDocumentationFromDeclaration(c, symbol, decl, decl, lsproto.MarkupKindPlainText, true /*commentOnly*/); doc != "" && !slices.Contains(parts, doc) {
+		documentationLocation := location
+		if documentationLocation == nil {
+			documentationLocation = decl
+		}
+		if doc := l.getDocumentationFromDeclaration(c, symbol, decl, documentationLocation, contentFormat, commentOnly); doc != "" && !slices.Contains(parts, doc) {
 			parts = append(parts, doc)
 		}
 	}