Consolidate constant expression nodes into a single type

- Instead of having ZCC_ExprString, ZCC_ExprInt, and ZCC_ExprFloat,
  just use a single ZCC_ExprConstant. It should simplify type
  promotion and constant folding in the future.

src/zscript/ast.cpp

@@ -442,10 +442,7 @@ static void OpenExprType(FLispString &out, EZCCExprType type)
 		"id",
 		"super",
 		"self",
-		"string-const",
-		"int-const",
-		"uint-const",
-		"float-const",
+		"const",
 		"func-call",
 		"array-access",
 		"member-access",
@@ -518,30 +515,23 @@ static void PrintExprID(FLispString &out, ZCC_TreeNode *node)
 	out.Close();
 }
 
-static void PrintExprString(FLispString &out, ZCC_TreeNode *node)
+static void PrintExprConstant(FLispString &out, ZCC_TreeNode *node)
 {
-	ZCC_ExprString *enode = (ZCC_ExprString *)node;
-	assert(enode->Operation == PEX_StringConst);
-	out.Open("expr-string-const");
-	PrintStringConst(out, *enode->Value);
-	out.Close();
+	ZCC_ExprConstant *enode = (ZCC_ExprConstant *)node;
+	assert(enode->Operation == PEX_ConstValue);
+	out.Open("expr-const");
+	if (enode->Type == TypeString)
+	{
+		PrintStringConst(out, *enode->StringVal);
 	}
-
-static void PrintExprInt(FLispString &out, ZCC_TreeNode *node)
+	else if (enode->Type == TypeFloat64)
 	{
-	ZCC_ExprInt *enode = (ZCC_ExprInt *)node;
-	assert(enode->Operation == PEX_IntConst || enode->Operation == PEX_UIntConst);
-	OpenExprType(out, enode->Operation);
-	out.AddInt(enode->Value);
-	out.Close();
+		out.AddFloat(enode->DoubleVal);
 	}
-
-static void PrintExprFloat(FLispString &out, ZCC_TreeNode *node)
+	else
 	{
-	ZCC_ExprFloat *enode = (ZCC_ExprFloat *)node;
-	assert(enode->Operation == PEX_FloatConst);
-	out.Open("expr-float-const");
-	out.AddFloat(enode->Value);
+		out.AddInt(enode->IntVal);
+	}
 	out.Close();
 }
 
@@ -817,9 +807,7 @@ void (* const TreeNodePrinter[NUM_AST_NODE_TYPES])(FLispString &, ZCC_TreeNode *
 	PrintClassType,
 	PrintExpression,
 	PrintExprID,
-	PrintExprString,
-	PrintExprInt,
-	PrintExprFloat,
+	PrintExprConstant,
 	PrintExprFuncCall,
 	PrintExprMemberAccess,
 	PrintExprUnary,

src/zscript/zcc-parse.lemon

@@ -726,7 +726,7 @@ const_def(X) ::= CONST(T) IDENTIFIER(A) EQ expr(B) SEMICOLON.
 %type expr{ZCC_Expression *}
 %type primary{ZCC_Expression *}
 %type unary_expr{ZCC_Expression *}
-%type constant{ZCC_Expression *}
+%type constant{ZCC_ExprConstant *}
 
 %include {
 #define UNARY_EXPR(X,T) NEW_AST_NODE(ExprUnary, expr, X); expr->Operation = T; expr->Operand = X; expr->Type = NULL
@@ -1091,22 +1091,22 @@ named_expr(X) ::= expr(B).
 /************ Constants ************/
 
 /* Allow C-like concatenation of adjacent string constants. */
-%type string_constant{ZCC_ExprString *}
+%type string_constant{ZCC_ExprConstant *}
 
 string_constant(X) ::= STRCONST(A).
 {
-	NEW_AST_NODE(ExprString, strconst, A);
-	strconst->Operation = PEX_StringConst;
+	NEW_AST_NODE(ExprConstant, strconst, A);
+	strconst->Operation = PEX_ConstValue;
 	strconst->Type = TypeString;
-	strconst->Value = A.String;
+	strconst->StringVal = A.String;
 	X = strconst;
 }
 string_constant(X) ::= string_constant(A) STRCONST(B).
 {
-	NEW_AST_NODE(ExprString, strconst, A);
-	strconst->Operation = PEX_StringConst;
+	NEW_AST_NODE(ExprConstant, strconst, A);
+	strconst->Operation = PEX_ConstValue;
 	strconst->Type = TypeString;
-	strconst->Value = stat->Strings.Alloc(*(A->Value) + *(B.String));
+	strconst->StringVal = stat->Strings.Alloc(*(A->StringVal) + *(B.String));
 	X = strconst;
 }
 
@@ -1116,18 +1116,18 @@ constant(X) ::= string_constant(A).
 }
 constant(X) ::= INTCONST(A).
 {
-	NEW_AST_NODE(ExprInt, intconst, A);
-	intconst->Operation = PEX_IntConst;
+	NEW_AST_NODE(ExprConstant, intconst, A);
+	intconst->Operation = PEX_ConstValue;
 	intconst->Type = TypeSInt32;
-	intconst->Value = A.Int;
+	intconst->IntVal = A.Int;
 	X = intconst;
 }
 constant(X) ::= FLOATCONST(A).
 {
-	NEW_AST_NODE(ExprFloat, floatconst, A);
-	floatconst->Operation = PEX_FloatConst;
+	NEW_AST_NODE(ExprConstant, floatconst, A);
+	floatconst->Operation = PEX_ConstValue;
 	floatconst->Type = TypeFloat64;
-	floatconst->Value = A.Float;
+	floatconst->DoubleVal = A.Float;
 	X = floatconst;
 }
 

src/zscript/zcc_parser.h

@@ -75,9 +75,7 @@ enum EZCCTreeNodeType
 	AST_ClassType,
 	AST_Expression,
 	AST_ExprID,
-	AST_ExprString,
-	AST_ExprInt,
-	AST_ExprFloat,
+	AST_ExprConstant,
 	AST_ExprFuncCall,
 	AST_ExprMemberAccess,
 	AST_ExprUnary,
@@ -136,10 +134,7 @@ enum EZCCExprType
 	PEX_ID,
 	PEX_Super,
 	PEX_Self,
-	PEX_StringConst,
-	PEX_IntConst,
-	PEX_UIntConst,
-	PEX_FloatConst,
+	PEX_ConstValue,
 	PEX_FuncCall,
 	PEX_ArrayAccess,
 	PEX_MemberAccess,
@@ -352,19 +347,14 @@ struct ZCC_ExprID : ZCC_Expression
 	ENamedName Identifier;
 };
 
-struct ZCC_ExprString : ZCC_Expression
+struct ZCC_ExprConstant : ZCC_Expression
 {
-	FString *Value;
+	union
+	{
+		FString *StringVal;
+		int IntVal;
+		double DoubleVal;
 	};
-
-struct ZCC_ExprInt : ZCC_Expression
-{
-	int Value;
-};
-
-struct ZCC_ExprFloat : ZCC_Expression
-{
-	double Value;
 };
 
 struct ZCC_FuncParm : ZCC_TreeNode