Shader/ShaderLang: Add type inference for variable declaration

src/Nazara/Shader/ShaderAstValidator.cpp

@@ -594,6 +594,21 @@ namespace Nz::ShaderAst
 		AstScopedVisitor::Visit(node);
 	}
 
+	void AstValidator::Visit(DeclareVariableStatement& node)
+	{
+		if (IsNoType(node.varType))
+		{
+			if (!node.initialExpression)
+				throw AstError{ "variable must either have a type or an initial value" };
+
+			node.initialExpression->Visit(*this);
+
+			node.varType = GetExpressionType(*node.initialExpression);
+		}
+
+		AstScopedVisitor::Visit(node);
+	}
+
 	void AstValidator::Visit(ExpressionStatement& node)
 	{
 		MandatoryExpr(node.expression);

src/Nazara/Shader/ShaderLangParser.cpp

@@ -637,15 +637,19 @@ namespace Nz::ShaderLang
 		Expect(Advance(), TokenType::Let);
 
 		std::string variableName = ParseIdentifierAsName();
+		RegisterVariable(variableName);
+
+		ShaderAst::ExpressionType variableType = ShaderAst::NoType{};
+		if (Peek().type == TokenType::Colon)
+		{
 			Expect(Advance(), TokenType::Colon);
-
-		Expect(Advance(), TokenType::Colon);
-
+
+			variableType = ParseType();
 		}
 
-		ShaderAst::ExpressionPtr expression;
+		ShaderAst::ExpressionPtr expression;
 		if (IsNoType(variableType) || Peek().type == TokenType::Assign)
-		{
+		{
 			Expect(Advance(), TokenType::Assign);
 			expression = ParseExpression();
 		}