diff --git a/parsercheck.cc b/parsercheck.cc
index a1a8cc1..63b7c7b 100644
--- a/parsercheck.cc
+++ b/parsercheck.cc
@@ -2,6 +2,7 @@
 #include "opast.hh"
 #include <ebcl/Files.hh>
 #include <ebcl/SRDText.hh>
+#include <ebcl/Algorithms.hh>
 
 using namespace ebcl;
 using namespace opast;
@@ -35,6 +36,121 @@ void WriteSRDError(
 
 /*============================================================================*/
 
+T_Array< T_SRDError > parserPrototypes(
+		T_OwnPtr< T_RootNode > const& root )
+{
+	T_Visitor< opast::A_Node > visitor{ ASTVisitorBrowser };
+	T_Array< T_SRDError > errors;
+
+	enum class E_DataType {
+		UNKNOWN ,
+		ALIAS ,
+		VARIABLE ,
+		FRAMEBUFFER ,
+		INPUT ,
+		PIPELINE ,
+		PROGRAM ,
+		TEXTURE ,
+	};
+	struct T_Decl_ {
+		E_DataType type;
+		T_SRDLocation location;
+
+		T_Decl_( const E_DataType dt ,
+				T_SRDLocation const& loc ) noexcept
+			: type( dt ) , location( loc )
+		{ }
+	};
+	T_KeyValueTable< T_String , T_Decl_ > type;
+
+	visitor.visit( *root , [&]( A_Node& node , bool exit ) -> bool {
+		if ( exit ) {
+			return false;
+		}
+
+		E_DataType dt{ E_DataType::UNKNOWN };
+		T_String id;
+		T_SRDLocation location;
+		switch ( node.type( ) ) {
+
+		    case A_Node::OP_FRAMEBUFFER:
+			dt = E_DataType::FRAMEBUFFER;
+			id = dynamic_cast< T_FramebufferInstrNode& >( node ).id( );
+			location = dynamic_cast< T_FramebufferInstrNode& >( node ).idLocation( );
+			break;
+
+		    case A_Node::OP_INPUT:
+			dt = E_DataType::INPUT;
+			id = dynamic_cast< T_InputInstrNode& >( node ).name( );
+			location = dynamic_cast< T_InputInstrNode& >( node ).nameLocation( );
+			break;
+
+		    case A_Node::OP_PIPELINE:
+			dt = E_DataType::PIPELINE;
+			id = dynamic_cast< T_PipelineInstrNode& >( node ).id( );
+			location = dynamic_cast< T_PipelineInstrNode& >( node ).idLocation( );
+			break;
+
+		    case A_Node::OP_PROGRAM:
+			dt = E_DataType::PROGRAM;
+			id = dynamic_cast< T_ProgramInstrNode& >( node ).id( );
+			location = dynamic_cast< T_ProgramInstrNode& >( node ).idLocation( );
+			break;
+
+		    case A_Node::OP_SET:
+			dt = E_DataType::VARIABLE;
+			id = dynamic_cast< T_SetInstrNode& >( node ).id( );
+			location = dynamic_cast< T_SetInstrNode& >( node ).idLocation( );
+			break;
+
+		    case A_Node::OP_TEXTURE:
+			dt = E_DataType::TEXTURE;
+			id = dynamic_cast< T_TextureInstrNode& >( node ).id( );
+			location = dynamic_cast< T_TextureInstrNode& >( node ).idLocation( );
+			break;
+
+		    // TODO: samplers
+
+		    default:
+			return !dynamic_cast< A_ExpressionNode* >( &node );
+		}
+
+		assert( dt != E_DataType::UNKNOWN );
+		T_Decl_ const* const existing( type.get( id ) );
+		if ( !existing ) {
+			type.add( id , T_Decl_{ dt , location } );
+		} else if ( existing->type != dt ) {
+			T_StringBuilder sb;
+			sb << "'" << id << "' redeclared as ";
+			switch ( dt ) {
+				case E_DataType::VARIABLE: sb << "variable"; break;
+				case E_DataType::FRAMEBUFFER: sb << "framebuffer"; break;
+				case E_DataType::INPUT: sb << "input"; break;
+				case E_DataType::PIPELINE: sb << "pipeline"; break;
+				case E_DataType::PROGRAM: sb << "program"; break;
+				case E_DataType::TEXTURE: sb << "texture"; break;
+				default: std::abort( );
+			}
+			sb << "; previous declaration as ";
+			switch ( existing->type ) {
+				case E_DataType::VARIABLE: sb << "variable"; break;
+				case E_DataType::FRAMEBUFFER: sb << "framebuffer"; break;
+				case E_DataType::INPUT: sb << "input"; break;
+				case E_DataType::PIPELINE: sb << "pipeline"; break;
+				case E_DataType::PROGRAM: sb << "program"; break;
+				case E_DataType::TEXTURE: sb << "texture"; break;
+				default: std::abort( );
+			}
+			sb << " at " << existing->location;
+			errors.addNew( std::move( sb ) , location );
+		}
+
+		return false;
+	} );
+
+	return errors;
+}
+
 
 /*============================================================================*/
 
@@ -76,8 +192,20 @@ int main( int argc , char** argv )
 	// Parse the fuck
 	T_Parser parser;
 	if ( parser.parse( srdOut.list( ) ) ) {
-		printf( "Success!\n" );
-		return 0;
+		printf( "Success - now running prototypes\n" );
+		T_Array< T_SRDError > errors{ parserPrototypes( parser.result( ) ) };
+		if ( errors.empty( ) ) {
+			printf( "Success!\n" );
+			return 0;
+		}
+
+		T_StringBuilder sb;
+		for ( auto const& err : errors ) {
+			WriteSRDError( sb , err );
+		}
+		sb << "Parser prototypes failed\n" << '\0';
+		fprintf( stderr , "%s" , sb.data( ) );
+		return 4;
 	} else {
 		T_StringBuilder sb;
 		for ( auto const& err : parser.errors( ) ) {