cgen/parser: fix unions

vlib/strconv/atof_test.v

@@ -74,5 +74,5 @@ fn test_atof() {
 	// DOUBLE_MINUS_ZERO
 	f1=-0.0
 	assert *ptr == u64(0x8000000000000000)
-	//println("DONE!")
+	println("DONE!")
 }

vlib/v/ast/ast.v

@@ -150,6 +150,7 @@ pub:
 	pub_pos       int // pub:
 	pub_mut_pos   int // pub mut:
 	is_c          bool
+	is_union bool
 }
 
 pub struct InterfaceDecl {

vlib/v/gen/cgen.v

@@ -460,7 +460,12 @@ fn (g mut Gen) stmt(node ast.Stmt) {
 			// g.writeln('\t$field_type_sym.name $field.name;')
 			// }
 			// g.writeln('} $name;')
-			if !it.is_c {
+			if it.is_c {
+				return
+			}
+			if it.is_union {
+				g.typedefs.writeln('typedef union $name $name;')
+			} else {
 				g.typedefs.writeln('typedef struct $name $name;')
 			}
 		}
@@ -2121,7 +2126,11 @@ fn (g mut Gen) write_types(types []table.TypeSymbol) {
 			table.Struct {
 				info := typ.info as table.Struct
 				// g.definitions.writeln('typedef struct {')
-				g.definitions.writeln('struct $name {')
+				if info.is_union {
+					g.definitions.writeln('union $name {')
+				} else {
+					g.definitions.writeln('struct $name {')
+				}
 				if info.fields.len > 0 {
 					for field in info.fields {
 						type_name := g.typ(field.typ)

vlib/v/parser/parser.v

@@ -1447,6 +1447,7 @@ fn (p mut Parser) struct_decl() ast.StructDecl {
 	if is_pub {
 		p.next()
 	}
+	is_union := p.tok.kind == .key_union
 	if p.tok.kind == .key_struct {
 		p.check(.key_struct)
 	} else {
@@ -1535,6 +1536,7 @@ fn (p mut Parser) struct_decl() ast.StructDecl {
 		info: table.Struct{
 			fields: fields
 			is_typedef: is_typedef
+			is_union: is_union
 		}
 	}
 	mut ret := 0
@@ -1558,6 +1560,7 @@ fn (p mut Parser) struct_decl() ast.StructDecl {
 		pub_pos: pub_pos
 		pub_mut_pos: pub_mut_pos
 		is_c: is_c
+		is_union: is_union
 	}
 }
 

vlib/v/table/atypes.v

@@ -540,6 +540,7 @@ pub struct Struct {
 pub mut:
 	fields []Field
 	is_typedef bool // C. [typedef]
+	is_union bool
 }
 
 pub struct Enum {