Mojom frontend: Compute, validate and populate struct field version info

mojom/mojom_parser/mojom/types.go

Index: mojom/mojom_parser/mojom/types.go
diff --git a/mojom/mojom_parser/mojom/types.go b/mojom/mojom_parser/mojom/types.go
index b2589fec3706d83f8f9916a57a3b039a13027469..fd22392feda2368103aae2c914d578d9aa985a2a 100644
--- a/mojom/mojom_parser/mojom/types.go
+++ b/mojom/mojom_parser/mojom/types.go
@@ -55,6 +55,7 @@ const (
 // A LiteralType is a |ConcreteType|.
 type LiteralType interface {
 	ConcreteType
+	LiteralTypeKind() TypeKind
 }
 
 // ConcreteType represents the type of a concrete value. These are the types
@@ -106,8 +107,9 @@ type TypeRef interface {
 	// or MapTypeRefs because those types are never validated after resolution.
 	IsAssignmentCompatible(assignedValue ConcreteValue) bool
 
-	// TypeName() returns a string appropriate for using-facing messages
-	// that names a type. For UserDefinedTypes it will return the fully-qualified
+	// TypeName() returns a string appropriate for user-facing messages
+	// that names a type, including markers for interface requests and nullability.
+	// For UserDefinedTypes it will return the fully-qualified
 	// name of the resolved type, if the identifier has already been resolved.
 	// Otherwise it will return the identifier.
 	TypeName() string
@@ -121,6 +123,9 @@ type TypeRef interface {
 	// type and for MapTypes this method returns the union of the set of UserDefined
 	// types of the key type and the value type.
 	ReferencedUserDefinedTypes() UserDefinedTypeSet
+
+	// Returns true just in case the type referene is nullable.
+	Nullable() bool
 }
 
 /////////////////////////////////////////////////////////////
@@ -185,12 +190,14 @@ func (SimpleType) MarkUsedAsMapKey() bool {
 	return true
 }
 
-// From interface TypeRef:
-
 func (SimpleType) MarkUsedAsConstantType() bool {
 	return true
 }
 
+func (SimpleType) Nullable() bool {
+	return false
+}
+
 // A SimpleType does not reference any UserDefinedTypes.
 func (SimpleType) ReferencedUserDefinedTypes() UserDefinedTypeSet {
 	return MakeUserDefinedTypeSet()
@@ -1217,6 +1224,19 @@ func int32Value(literalValue LiteralValue) (int32Value int32, ok bool) {
 	return
 }
 
+// uint32Value returns the value of |literalValue| as an uint32.
+// If the type of |literalValue| is not an integer type then |ok|
+// will be false and |int32Value| will be zero. If the type of
+// |literalValue| is any of the integer types then |uint32Value| will
+// be the integer value cast to an uint32 and |ok| will indicate whether
+// or not the pre-cast value is between 0 and math.MaxUInt32.
+func uint32Value(literalValue LiteralValue) (int32Value uint32, ok bool) {
+	int64Value, ok := int64Value(literalValue)
+	ok = ok && int64Value <= math.MaxUint32 && int64Value >= 0
+	int32Value = uint32(int64Value)
+	return
+}
+
 func MakeStringLiteralValue(text string, token *lexer.Token) LiteralValue {
 	return LiteralValue{StringLiteralType, text, false, token}
 }