Fix a bunch of type alias related autocompletion problems. Add tests.

#479

_testing/DESC

@@ -58,3 +58,6 @@ test.0057 - embedded interfaces
 test.0058 - canonical import aliases
 test.0059 - canonical import aliases, more complicated case (doesn't work as you might expect)
 test.0060 - shortcut syntax for return value types in functions
+test.0061 - function body vs struct literal cursor context detection
+test.0062 - struct type alias embedding
+test.0063 - fields autocompletion for a struct literal which is defined by a type alias

_testing/test.0062/out.expected

@@ -0,0 +1,5 @@
+Found 4 candidates:
+  var A int
+  var ABCAlias ABCAlias
+  var B int
+  var C int

_testing/test.0062/test.go.in

@@ -0,0 +1,18 @@
+package main
+
+type ABC struct {
+	A int
+	B int
+	C int
+}
+
+type ABCAlias = ABC
+
+type Foo struct {
+	ABCAlias
+}
+
+func main() {
+	foo := Foo{}
+	foo.
+}

_testing/test.0063/out.expected

@@ -0,0 +1,4 @@
+Found 3 candidates:
+  var A int
+  var B int
+  var C int

_testing/test.0063/test.go.in

@@ -0,0 +1,15 @@
+package main
+
+type ABC struct {
+	A int
+	B int
+	C int
+}
+
+type ABCAlias = ABC
+
+func main() {
+	x := ABCAlias{
+
+	}
+}

autocompletecontext.go

@@ -110,6 +110,11 @@ func (b *out_buffers) append_embedded(p string, decl *decl, pkg string, class de
 			continue
 		}
 
+		// could be type alias
+		if typedecl.is_alias() {
+			typedecl = typedecl.type_dealias()
+		}
+
 		// prevent infinite recursion here
 		if typedecl.is_visited() {
 			continue

cursorcontext.go

@@ -286,7 +286,14 @@ func (c *auto_complete_context) deduce_struct_type_decl(iter *token_iterator) *d
 	if decl == nil {
 		return nil
 	}
-	if _, ok := decl.typ.(*ast.StructType); !ok {
+
+	// we allow only struct types here, but also support type aliases
+	if decl.is_alias() {
+		dd := decl.type_dealias()
+		if _, ok := dd.typ.(*ast.StructType); !ok {
+			return nil
+		}
+	} else if _, ok := decl.typ.(*ast.StructType); !ok {
 		return nil
 	}
 	return decl