diff --git a/Rez/CMakeLists.txt b/Rez/CMakeLists.txt
index 0c7a08f08a..0bb65a0885 100644
--- a/Rez/CMakeLists.txt
+++ b/Rez/CMakeLists.txt
@@ -56,6 +56,8 @@ add_library(RezLib
 		ResourceCompiler.h
 
 		ResSpec.h
+
+		Diagnostic.h Diagnostic.cc
 	)
 target_link_libraries(RezLib ResourceFiles ${Boost_LIBRARIES})
 
diff --git a/Rez/Diagnostic.cc b/Rez/Diagnostic.cc
new file mode 100644
index 0000000000..3d8d2ab107
--- /dev/null
+++ b/Rez/Diagnostic.cc
@@ -0,0 +1,17 @@
+#include "Diagnostic.h"
+
+Diagnostic::Diagnostic()
+{
+}
+
+Diagnostic::Diagnostic(Severity sev, std::string msg, yy::location loc)
+	: severity(sev), message(msg), location(loc)
+{
+
+}
+
+
+std::ostream &operator<<(std::ostream &out, const Diagnostic &d)
+{
+	return out << d.location << ": " << d.message;
+}
diff --git a/Rez/Diagnostic.h b/Rez/Diagnostic.h
new file mode 100644
index 0000000000..3e0b442089
--- /dev/null
+++ b/Rez/Diagnostic.h
@@ -0,0 +1,31 @@
+#ifndef DIAGNOSTIC_H
+#define DIAGNOSTIC_H
+
+#include <string>
+#include <iosfwd>
+#include "location.hh"
+
+class Diagnostic
+{
+public:
+	enum Severity
+	{
+		warning,
+		error,
+		fatalError
+	};
+
+	Diagnostic();
+	Diagnostic(Severity sev, std::string msg, yy::location loc);
+
+private:
+	Severity severity;
+	std::string message;
+	yy::location location;
+
+	friend std::ostream& operator<<(std::ostream&, const Diagnostic&);
+};
+
+std::ostream& operator<<(std::ostream&, const Diagnostic&);
+
+#endif // DIAGNOSTIC_H
diff --git a/Rez/Expression.cc b/Rez/Expression.cc
index 636f6e8547..808d0557be 100644
--- a/Rez/Expression.cc
+++ b/Rez/Expression.cc
@@ -3,21 +3,29 @@
 #include <cassert>
 #include <iostream>
 #include <fstream>
+#include "Diagnostic.h"
 
 int Expression::evaluateInt(ResourceCompiler *ctx)
 {
-	throw TypeError();
+	error(ctx, "Expected an integer or integer expression here.");
+	return 0;
 }
 
 std::string Expression::evaluateString(ResourceCompiler *ctx)
 {
-	throw TypeError();
+	error(ctx, "Expected a string or string expression here.");
+	return "";
 }
 
 Expression::~Expression()
 {
 }
 
+void Expression::error(ResourceCompiler *ctx, std::string err)
+{
+	ctx->problem(Diagnostic(Diagnostic::Severity::error, err, location));
+}
+
 
 StringExpr::~StringExpr()
 {
@@ -80,8 +88,8 @@ int BinaryExpr::evaluateInt(ResourceCompiler *ctx)
 		case BinaryOp::DIVIDE:
 			return a->evaluateInt(ctx) / b->evaluateInt(ctx);
 		default:
-			throw TypeError();
-			break;
+			error(ctx, "Expected an integer or integer expression here.");
+			return 0;
 	}
 }
 
@@ -92,8 +100,8 @@ std::string BinaryExpr::evaluateString(ResourceCompiler *ctx)
 		case BinaryOp::CONCAT:
 			return a->evaluateString(ctx) + b->evaluateString(ctx);
 		default:
-			throw TypeError();
-			break;
+			error(ctx, "Expected a string or string expression here.");
+			return "";
 	}
 }
 
@@ -111,14 +119,14 @@ int UnaryExpr::evaluateInt(ResourceCompiler *ctx)
 		case UnaryOp::COMPLEMENT:
 			return ~a->evaluateInt(ctx);
 		default:
-			throw TypeError();
-			break;
+			error(ctx, "Expected an integer or integer expression here.");
+			return 0;
 	}
 }
 
 
-IdentifierExpr::IdentifierExpr(std::string id)
-	: id(id)
+IdentifierExpr::IdentifierExpr(std::string id, yy::location loc)
+	: Expression(loc), id(id)
 {
 }
 
@@ -133,7 +141,8 @@ ExprPtr IdentifierExpr::lookup(ResourceCompiler *ctx)
 	for(auto arg : arguments)
 		sub.addSubscript(arg->evaluateInt(ctx));
 	ExprPtr val = ctx->lookupIdentifier(id, sub);
-	assert(val);
+	if(!val)
+		error(ctx, "Identifier \"" + id + "\" is not defined.");
 	return val;
 }
 
@@ -141,17 +150,23 @@ int IdentifierExpr::evaluateInt(ResourceCompiler *ctx)
 {
 	if(ctx->isPrePass())
 		return 0;
-	return lookup(ctx)->evaluateInt(ctx);
+	if(ExprPtr e = lookup(ctx))
+		return e->evaluateInt(ctx);
+	else
+		return 0;
 }
 
 std::string IdentifierExpr::evaluateString(ResourceCompiler *ctx)
 {
-	return lookup(ctx)->evaluateString(ctx);
+	if(ExprPtr e = lookup(ctx))
+		return e->evaluateString(ctx);
+	else
+		return "";
 }
 
 
-CaseExpr::CaseExpr(const std::string &tag, CompoundExprPtr expr)
-	: tag(tag), expr(expr)
+CaseExpr::CaseExpr(const std::string &tag, CompoundExprPtr expr, yy::location loc)
+	: Expression(loc), tag(tag), expr(expr)
 {
 }
 
@@ -193,15 +208,16 @@ std::string UnimplementedExpr::evaluateString(ResourceCompiler *ctx)
 }
 
 
-PeekExpr::PeekExpr(ExprPtr addr, ExprPtr offset, ExprPtr size)
-	: addr(addr), offset(offset), size(size)
+PeekExpr::PeekExpr(ExprPtr addr, ExprPtr offset, ExprPtr size, yy::location loc)
+	: Expression(loc), addr(addr), offset(offset), size(size)
 {
 }
 
-PeekExpr::PeekExpr(ExprPtr addr, int size)
-	: addr(addr),
-	  offset(std::make_shared<IntExpr>(0)),
-	  size(std::make_shared<IntExpr>(size))
+PeekExpr::PeekExpr(ExprPtr addr, int size, yy::location loc)
+	: Expression(loc),
+	  addr(addr),
+	  offset(std::make_shared<IntExpr>(0,loc)),
+	  size(std::make_shared<IntExpr>(size,loc))
 {
 }
 
diff --git a/Rez/Expression.h b/Rez/Expression.h
index 0300ec6aec..f9572a250c 100644
--- a/Rez/Expression.h
+++ b/Rez/Expression.h
@@ -4,6 +4,8 @@
 #include <memory>
 #include <vector>
 
+#include "location.hh"
+
 class ResourceCompiler;
 
 class Expression;
@@ -33,16 +35,22 @@ class TypeError
 class Expression
 {
 public:
+	yy::location location;
+
+	Expression(yy::location loc) : location(loc) {}
+
 	virtual int evaluateInt(ResourceCompiler *ctx);
 	virtual std::string evaluateString(ResourceCompiler *ctx);
 	virtual ~Expression();
+
+	void error(ResourceCompiler *ctx, std::string err);
 };
 
 class StringExpr : public Expression
 {
 	std::string str;
 public:
-	StringExpr(const std::string& str) : str(str) {}
+	StringExpr(const std::string& str, yy::location loc) : Expression(loc), str(str) {}
 	~StringExpr();
 	virtual std::string evaluateString(ResourceCompiler *ctx);
 };
@@ -51,7 +59,7 @@ class IntExpr : public Expression
 {
 	int val;
 public:
-	IntExpr(int val) : val(val) {}
+	IntExpr(int val, yy::location loc) : Expression(loc), val(val) {}
 	~IntExpr();
 
 	virtual int evaluateInt(ResourceCompiler *ctx);
@@ -61,6 +69,8 @@ class CompoundExpr : public Expression
 {
 	std::vector<ExprPtr> items;
 public:
+	CompoundExpr(yy::location loc) : Expression(loc) {}
+
 	void addItem(ExprPtr item);
 	ExprPtr getItem(int i) const { return items[i]; }
 	int size() const { return items.size(); }
@@ -74,7 +84,7 @@ class CaseExpr : public Expression
 	CompoundExprPtr expr;
 	friend class SwitchField;
 public:
-	CaseExpr(const std::string& tag, CompoundExprPtr expr);
+	CaseExpr(const std::string& tag, CompoundExprPtr expr, yy::location loc);
 };
 
 class BinaryExpr : public Expression
@@ -82,8 +92,8 @@ class BinaryExpr : public Expression
 	BinaryOp op;
 	ExprPtr a, b;
 public:
-	BinaryExpr(BinaryOp op, ExprPtr a, ExprPtr b)
-		: op(op), a(a), b(b) {}
+	BinaryExpr(BinaryOp op, ExprPtr a, ExprPtr b, yy::location loc)
+		: Expression(loc), op(op), a(a), b(b) {}
 	~BinaryExpr();
 
 	virtual int evaluateInt(ResourceCompiler *ctx);
@@ -95,8 +105,8 @@ class UnaryExpr : public Expression
 	UnaryOp op;
 	ExprPtr a;
 public:
-	UnaryExpr(UnaryOp op, ExprPtr a)
-		: op(op), a(a) {}
+	UnaryExpr(UnaryOp op, ExprPtr a, yy::location loc)
+		: Expression(loc), op(op), a(a) {}
 	~UnaryExpr();
 
 	virtual int evaluateInt(ResourceCompiler *ctx);
@@ -107,7 +117,7 @@ class IdentifierExpr : public Expression
 public:
 	std::string id;
 	std::vector<ExprPtr> arguments;
-	IdentifierExpr(std::string id);
+	IdentifierExpr(std::string id, yy::location loc);
 
 	void addArgument(ExprPtr e);
 	ExprPtr lookup(ResourceCompiler *ctx);
@@ -119,7 +129,7 @@ class CountOfExpr : public Expression
 {
 	IdentifierExprPtr arg;
 public:
-	CountOfExpr(IdentifierExprPtr arg) : arg(arg) {}
+	CountOfExpr(IdentifierExprPtr arg, yy::location loc) : Expression(loc), arg(arg) {}
 	virtual int evaluateInt(ResourceCompiler *ctx);
 };
 
@@ -127,7 +137,7 @@ class ArrayIndexExpr : public Expression
 {
 	IdentifierExprPtr arg;
 public:
-	ArrayIndexExpr(IdentifierExprPtr arg) : arg(arg) {}
+	ArrayIndexExpr(IdentifierExprPtr arg, yy::location loc) : Expression(loc), arg(arg) {}
 	virtual int evaluateInt(ResourceCompiler *ctx);
 };
 
@@ -135,7 +145,7 @@ class ReadExpr : public Expression
 {
 	ExprPtr arg;
 public:
-	ReadExpr(ExprPtr arg) : arg(arg) {}
+	ReadExpr(ExprPtr arg, yy::location loc) : Expression(loc), arg(arg) {}
 	virtual std::string evaluateString(ResourceCompiler *ctx);
 };
 
@@ -143,7 +153,7 @@ class UnimplementedExpr : public Expression
 {
 	std::string msg;
 public:
-	UnimplementedExpr(std::string msg) : msg(msg) {}
+	UnimplementedExpr(std::string msg, yy::location loc) : Expression(loc), msg(msg) {}
 	virtual int evaluateInt(ResourceCompiler *ctx);
 	virtual std::string evaluateString(ResourceCompiler *ctx);
 };
@@ -154,8 +164,8 @@ class PeekExpr : public Expression
 	ExprPtr offset;
 	ExprPtr size;
 public:
-	PeekExpr(ExprPtr addr, ExprPtr offset, ExprPtr size);
-	PeekExpr(ExprPtr addr, int size);
+	PeekExpr(ExprPtr addr, ExprPtr offset, ExprPtr size, yy::location loc);
+	PeekExpr(ExprPtr addr, int size, yy::location loc);
 	virtual int evaluateInt(ResourceCompiler *ctx);
 };
 
diff --git a/Rez/ResourceCompiler.cc b/Rez/ResourceCompiler.cc
index f332d91d4e..0d77436dd5 100644
--- a/Rez/ResourceCompiler.cc
+++ b/Rez/ResourceCompiler.cc
@@ -1,10 +1,13 @@
 #include "ResourceCompiler.h"
 #include <iostream>
 #include "ResourceDefinitions.h"
+#include "RezWorld.h"
+#include "Diagnostic.h"
 
 ResourceCompiler::ResourceCompiler(
-		TypeDefinitionPtr type, CompoundExprPtr body, bool verboseFlag)
-	: typeDefinition(type),
+		RezWorld& world, TypeDefinitionPtr type, CompoundExprPtr body, bool verboseFlag)
+	: world(world),
+	  typeDefinition(type),
 	  body(body),
 	  currentField(nullptr)
 {
@@ -99,14 +102,14 @@ ExprPtr ResourceCompiler::lookupIdentifier(std::string name, const Subscripts &s
 	if(p != labelValues.end())
 		return p->second;
 
-	std::cerr << "ID lookup failed: " << name << std::endl;
+	//std::cerr << "ID lookup failed: " << name << std::endl;
 
 	return nullptr;
 }
 
 void ResourceCompiler::defineLabel(const std::string &name)
 {
-	labelValues[std::make_pair(name,currentSubscripts)] = std::make_shared<IntExpr>(currentOffset);
+	labelValues[std::make_pair(name,currentSubscripts)] = std::make_shared<IntExpr>(currentOffset, yy::location());
 }
 
 void ResourceCompiler::compile()
@@ -142,6 +145,11 @@ int ResourceCompiler::getArrayIndex(const std::string &arrayName)
 	return curArrayIndices[arrayName];
 }
 
+void ResourceCompiler::problem(Diagnostic d)
+{
+	world.problem(d);
+}
+
 void ResourceCompiler::beginArrayScope(std::string &arrayName, int index)
 {
 	if(arrayName != "")
diff --git a/Rez/ResourceCompiler.h b/Rez/ResourceCompiler.h
index 6b11777dac..890a564db5 100644
--- a/Rez/ResourceCompiler.h
+++ b/Rez/ResourceCompiler.h
@@ -5,7 +5,8 @@
 #include "ResourceDefinitions.h"
 
 class Field;
-
+class RezWorld;
+class Diagnostic;
 
 class Subscripts
 {
@@ -45,6 +46,7 @@ public:
 
 class ResourceCompiler : public BinaryOutput
 {
+	RezWorld& world;
 	TypeDefinitionPtr typeDefinition;
 	CompoundExprPtr body;
 	std::map<std::pair<std::string, Subscripts>, ExprPtr> labelValues;
@@ -53,13 +55,9 @@ class ResourceCompiler : public BinaryOutput
 	Field* currentField;
 	Subscripts currentSubscripts;
 
-
-
 	void beginArrayScope(std::string& arrayName, int index);
-
 public:
-	ResourceCompiler(TypeDefinitionPtr type, CompoundExprPtr body, bool verboseFlag);
-
+	ResourceCompiler(RezWorld& world, TypeDefinitionPtr type, CompoundExprPtr body, bool verboseFlag);
 
 	ExprPtr lookupIdentifier(std::string name, const Subscripts& sub = Subscripts());
 
@@ -87,6 +85,8 @@ public:
 			: compiler(compiler) { compiler->beginArrayScope(arrayName, index); }
 		~ArrayScope() { compiler->currentSubscripts.popSubscript(); }
 	};
+
+	void problem(Diagnostic d);
 };
 
 
diff --git a/Rez/ResourceDefinitions.cc b/Rez/ResourceDefinitions.cc
index 50d663abcb..1ae315456c 100644
--- a/Rez/ResourceDefinitions.cc
+++ b/Rez/ResourceDefinitions.cc
@@ -20,14 +20,15 @@ FieldList::~FieldList()
 
 }
 
-void FieldList::addField(FieldPtr field)
+void FieldList::addField(FieldPtr field, yy::location loc)
 {
+	field->location = loc;
 	fields.push_back(field);
 }
 
-void FieldList::addLabel(std::string name)
+void FieldList::addLabel(std::string name, yy::location loc)
 {
-	addField(std::make_shared<LabelField>(name));
+	addField(std::make_shared<LabelField>(name), loc);
 }
 
 void FieldList::compile(ExprPtr expr, ResourceCompiler *compiler, bool prePass)
@@ -52,9 +53,9 @@ void SimpleField::addNamedValue(std::string n)
 {
 	if(lastNamedValue)
 		addNamedValue(n, std::make_shared<BinaryExpr>(
-			BinaryOp::PLUS, lastNamedValue, std::make_shared<IntExpr>(1)));
+			BinaryOp::PLUS, lastNamedValue, std::make_shared<IntExpr>(1, yy::location()), yy::location()));
 	else
-		addNamedValue(n, std::make_shared<IntExpr>(0));
+		addNamedValue(n, std::make_shared<IntExpr>(0, yy::location()));
 }
 
 void SimpleField::addNamedValue(std::string n, ExprPtr val)
@@ -200,8 +201,12 @@ void SimpleField::compileCompound(ExprPtr expr, ResourceCompiler *compiler, bool
 	}
 
 	CompoundExprPtr compound = std::dynamic_pointer_cast<CompoundExpr>(val);
+	if(!compound || compound->size() != count)
+	{
+		expr->error(compiler, std::string("expected ") + (type == Type::rect ? "rect {t,l,b,r}." : "point {v,h}."));
+		return;
+	}
 	assert(compound);
-
 	assert(compound->size() == count);
 
 	for(int i = 0; i < count; i++)
diff --git a/Rez/ResourceDefinitions.h b/Rez/ResourceDefinitions.h
index e2d5bb828f..cf84b26a38 100644
--- a/Rez/ResourceDefinitions.h
+++ b/Rez/ResourceDefinitions.h
@@ -8,6 +8,7 @@
 #include "Expression.h"
 #include "ResType.h"
 
+#include "location.hh"
 
 class TypeSpec
 {
@@ -44,6 +45,8 @@ class ResourceCompiler;
 class Field
 {
 public:
+	yy::location location;
+
 	virtual bool needsValue() { return true; }
 
 	virtual void compile(ExprPtr expr, ResourceCompiler *compiler, bool prePass) = 0;
@@ -129,8 +132,8 @@ protected:
 	std::vector<FieldPtr> fields;
 public:
 	virtual ~FieldList();
-	void addField(FieldPtr field);
-	void addLabel(std::string name);
+	void addField(FieldPtr field, yy::location loc);
+	void addLabel(std::string name, yy::location loc);
 
 	virtual void compile(ExprPtr expr, ResourceCompiler *compiler, bool prePass);
 };
diff --git a/Rez/RezParser.yy b/Rez/RezParser.yy
index 0b6e9d49af..67fe8ad5b0 100644
--- a/Rez/RezParser.yy
+++ b/Rez/RezParser.yy
@@ -198,9 +198,9 @@ type_spec : res_type { $$ = TypeSpec($res_type); }
 		  ;
 
 field_definitions	: %empty
-					| field_definitions IDENTIFIER ":"			{ world.fieldLists.top()->addLabel($2); }
+					| field_definitions IDENTIFIER ":"			{ world.fieldLists.top()->addLabel($2, @2); }
 					| field_definitions ";"
-					| field_definitions field_definition ";"	{ world.fieldLists.top()->addField($2); }
+					| field_definitions field_definition ";"	{ world.fieldLists.top()->addField($2, @2); }
 					;
 
 %type <FieldPtr> field_definition;
@@ -328,71 +328,71 @@ switch_case : "case" IDENTIFIER ":"
 
 
 value	: expression	{ $$ = $1; }
-		| "{" resource_body "}"	{ $$ = $2; }
+		| "{" resource_body "}"	{ $$ = $2; $$->location = @0; }
 		| string_expression { $$ = $1; }
 		;
 
 expression	: expression1	{ $$ = $1; }
-			| expression "^" expression1	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::XOR, $1, $3); }
+			| expression "^" expression1	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::XOR, $1, $3, @0); }
 			;
 
 expression1	: expression2	{ $$ = $1; }
-			| expression1 "&" expression2	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::AND, $1, $3); }
+			| expression1 "&" expression2	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::AND, $1, $3, @0); }
 			;
 
 expression2 : expression3	{ $$ = $1; }
-			| expression2 "|" expression3	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::OR, $1, $3); }
+			| expression2 "|" expression3	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::OR, $1, $3, @0); }
 			;
 
 expression3 : expression4	{ $$ = $1; }
-			| expression3 "==" expression4	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::EQUAL, $1, $3); }
-			| expression3 "!=" expression4	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::NOTEQUAL, $1, $3); }
+			| expression3 "==" expression4	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::EQUAL, $1, $3, @0); }
+			| expression3 "!=" expression4	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::NOTEQUAL, $1, $3, @0); }
 			;
 
 expression4 : expression5	{ $$ = $1; }
-			| expression4 ">>" expression5	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::SHIFTRIGHT, $1, $3); }
-			| expression4 "<<" expression5	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::SHIFTLEFT, $1, $3); }
+			| expression4 ">>" expression5	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::SHIFTRIGHT, $1, $3, @0); }
+			| expression4 "<<" expression5	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::SHIFTLEFT, $1, $3, @0); }
 			;
 
 expression5 : expression6	{ $$ = $1; }
-			| expression5 "+" expression6	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::PLUS, $1, $3); }
-			| expression5 "-" expression6	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::MINUS, $1, $3); }
+			| expression5 "+" expression6	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::PLUS, $1, $3, @0); }
+			| expression5 "-" expression6	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::MINUS, $1, $3, @0); }
 			;
 
 expression6 : expression7	{ $$ = $1; }
-			| expression6 "*" expression7	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::MULTIPLY, $1, $3); }
-			| expression6 "/" expression7	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::DIVIDE, $1, $3); }
+			| expression6 "*" expression7	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::MULTIPLY, $1, $3, @0); }
+			| expression6 "/" expression7	{ $$ = std::make_shared<BinaryExpr>(BinaryOp::DIVIDE, $1, $3, @0); }
 			;
 expression7	: expression8		{ $$ = $1; }
-			| "-" expression7	{ $$ = std::make_shared<UnaryExpr>(UnaryOp::MINUS, $2); }
+			| "-" expression7	{ $$ = std::make_shared<UnaryExpr>(UnaryOp::MINUS, $2, @0); }
 			| "+" expression7	{ $$ = $2; }
-			| "~" expression7	{ $$ = std::make_shared<UnaryExpr>(UnaryOp::COMPLEMENT, $2); }
+			| "~" expression7	{ $$ = std::make_shared<UnaryExpr>(UnaryOp::COMPLEMENT, $2, @0); }
 			;
 
-expression8	: INTLIT	{ $$ = std::make_shared<IntExpr>($1); }
-			| CHARLIT	{ $$ = std::make_shared<IntExpr>($1); }
+expression8	: INTLIT	{ $$ = std::make_shared<IntExpr>($1, @1); }
+			| CHARLIT	{ $$ = std::make_shared<IntExpr>($1, @1); }
 
 			| identifier_expression	{ $$ = $1; }
 			| "(" expression ")"	{ $$ = $2; }
 
 			| "$$countof" "(" identifier_expression ")"
-				{ $$ = std::make_shared<CountOfExpr>($identifier_expression); }
+				{ $$ = std::make_shared<CountOfExpr>($identifier_expression, @0); }
 			| "$$arrayindex" "(" identifier_expression ")"
-				{ $$ = std::make_shared<ArrayIndexExpr>($identifier_expression); }
+				{ $$ = std::make_shared<ArrayIndexExpr>($identifier_expression, @0); }
 			| "$$bitfield" "(" expression "," expression "," expression ")"
-				{ $$ = std::make_shared<PeekExpr>($3, $5, $7); }
+				{ $$ = std::make_shared<PeekExpr>($3, $5, $7, @0); }
 			| "$$word" "(" expression ")"
-				{ $$ = std::make_shared<PeekExpr>($3, 16); }
+				{ $$ = std::make_shared<PeekExpr>($3, 16, @0); }
 			| "$$byte" "(" expression ")"
-				{ $$ = std::make_shared<PeekExpr>($3, 8); }
+				{ $$ = std::make_shared<PeekExpr>($3, 8, @0); }
 			| "$$long" "(" expression ")"
-				{ $$ = std::make_shared<PeekExpr>($3, 32); }
+				{ $$ = std::make_shared<PeekExpr>($3, 32, @0); }
 			;
 
 %type <IdentifierExprPtr> identifier_expression;
-identifier_expression	: IDENTIFIER	{ $$ = std::make_shared<IdentifierExpr>($1); }
+identifier_expression	: IDENTIFIER	{ $$ = std::make_shared<IdentifierExpr>($1, @1); }
 						| IDENTIFIER
-							{ world.functionCalls.push(std::make_shared<IdentifierExpr>($1)); }
+							{ world.functionCalls.push(std::make_shared<IdentifierExpr>($1, @1)); }
 							"[" function_argument_list1 "]"
 							{ $$ = world.functionCalls.top(); world.functionCalls.pop(); }
 						;
@@ -407,7 +407,7 @@ function_argument_list1 : expression
 %type <ExprPtr> string_expression string_expression1;
 string_expression	: string_expression1	{ $$ = $1; }
 					| string_expression string_expression1
-						{ $$ = std::make_shared<BinaryExpr>(BinaryOp::CONCAT, $1, $2); }
+						{ $$ = std::make_shared<BinaryExpr>(BinaryOp::CONCAT, $1, $2, @0); }
 					;
 
 %type <std::string> stringlit;
@@ -415,14 +415,14 @@ stringlit	: STRINGLIT { $$ = $1; }
 			| DOLLAR STRINGLIT { $$ = fromHex($2); }
 			;
 
-string_expression1	:	stringlit	{ $$ = std::make_shared<StringExpr>($1); }
+string_expression1	:	stringlit	{ $$ = std::make_shared<StringExpr>($1, @1); }
 					|	"$$read" "(" string_expression ")"
-						{ $$ = std::make_shared<ReadExpr>($string_expression); }
+						{ $$ = std::make_shared<ReadExpr>($string_expression, @0); }
 					;
 
 resource	: "resource" res_spec "{" resource_body "}"
 			{
-				world.addResource($res_spec, $resource_body);
+				world.addResource($res_spec, $resource_body, @0);
 			}
 			;
 
@@ -439,23 +439,23 @@ resource_attributes	: %empty { $$ = [](ResSpec s){ return s; }; }
 					;
 
 %type <CompoundExprPtr> resource_body resource_body1;
-resource_body	: %empty { $$ = std::make_shared<CompoundExpr>(); }
-				| resource_body1 { $$ = $1; }
+resource_body	: %empty { $$ = std::make_shared<CompoundExpr>(@0); }
+				| resource_body1 { $$ = $1; $$->location = @1; }
 				;
-resource_body1	: resource_item	{ $$ = std::make_shared<CompoundExpr>(); $$->addItem($1); }
+resource_body1	: resource_item	{ $$ = std::make_shared<CompoundExpr>(@1); $$->addItem($1); }
 				| resource_body1 "," resource_item	{ $$ = $1; $$->addItem($3); }
 				| resource_body1 ";" resource_item	{ $$ = $1; $$->addItem($3); }
 				| resource_body1 ";" { $$ = $1; }
 				;
 
 resource_item	: value { $$ = $1; }
-				| IDENTIFIER "{" resource_body "}" { $$ = std::make_shared<CaseExpr>($IDENTIFIER, $resource_body); }
+				| IDENTIFIER "{" resource_body "}" { $$ = std::make_shared<CaseExpr>($IDENTIFIER, $resource_body, @0); }
 				;
 
 
 data : "data" res_spec "{" string_expression "}"
 {
-	world.addData($res_spec, $string_expression->evaluateString(nullptr));
+	world.addData($res_spec, $string_expression->evaluateString(nullptr), @0);
 }
 ;
 
diff --git a/Rez/RezWorld.cc b/Rez/RezWorld.cc
index 273eecb527..ae21be0d91 100644
--- a/Rez/RezWorld.cc
+++ b/Rez/RezWorld.cc
@@ -4,6 +4,8 @@
 
 #include <iostream>
 
+#include "Diagnostic.h"
+
 RezWorld::RezWorld()
 	: verboseFlag(false)
 {
@@ -14,7 +16,7 @@ void RezWorld::addTypeDefinition(TypeSpec spec, TypeDefinitionPtr type)
 	types[spec] = type;
 }
 
-TypeDefinitionPtr RezWorld::getTypeDefinition(ResType type, int id)
+TypeDefinitionPtr RezWorld::getTypeDefinition(ResType type, int id, yy::location loc)
 {
 	auto p = types.find(TypeSpec(type, id));
 	if(p != types.end())
@@ -22,24 +24,31 @@ TypeDefinitionPtr RezWorld::getTypeDefinition(ResType type, int id)
 	p = types.find(TypeSpec(type));
 	if(p != types.end())
 		return p->second;
+	problem(Diagnostic(Diagnostic::Severity::error, "Can't find type definition for '" + std::string(type) + "'", loc));
 
 	return nullptr;
 }
 
-void RezWorld::addResource(ResSpec spec, CompoundExprPtr body)
+void RezWorld::addResource(ResSpec spec, CompoundExprPtr body, yy::location loc)
 {
 	if(verboseFlag)
 		std::cout << "RESOURCE " << spec.type() << "(" << spec.id() << ", " << "\"" << spec.name() << "\"" << spec.attr() << ")" << std::endl;
-	TypeDefinitionPtr def = getTypeDefinition(spec.type(), spec.id());
-	ResourceCompiler compiler(def, body, verboseFlag);
+	TypeDefinitionPtr def = getTypeDefinition(spec.type(), spec.id(), loc);
+
+	ResourceCompiler compiler(*this, def, body, verboseFlag);
 	compiler.compile();
 
 	resources.addResource(Resource(spec.type(), spec.id(), compiler.resourceData(), spec.name(), spec.attr()));
 }
 
-void RezWorld::addData(ResSpec spec, const std::string &data)
+void RezWorld::addData(ResSpec spec, const std::string &data, yy::location loc)
 {
 	if(verboseFlag)
 		std::cout << "DATA " << spec.type() << "(" << spec.id() << ", " << "\"" << spec.name() << "\"" << spec.attr() << ")" << std::endl;
 	resources.addResource(Resource(spec.type(), spec.id(), data, spec.name(), spec.attr()));
 }
+
+void RezWorld::problem(Diagnostic d)
+{
+	std::cerr << d << std::endl;
+}
diff --git a/Rez/RezWorld.h b/Rez/RezWorld.h
index ee8044f5e1..0c32b687f4 100644
--- a/Rez/RezWorld.h
+++ b/Rez/RezWorld.h
@@ -9,6 +9,8 @@
 #include "ResourceFork.h"
 #include "ResSpec.h"
 
+class Diagnostic;
+
 class RezWorld
 {
 	friend class RezParser;
@@ -19,18 +21,21 @@ class RezWorld
 	std::stack<SwitchFieldPtr> switches;
 
 	Resources resources;
+
 public:
 	RezWorld();
 	void addTypeDefinition(TypeSpec spec, TypeDefinitionPtr type);
 
-	TypeDefinitionPtr getTypeDefinition(ResType type, int id);
+	TypeDefinitionPtr getTypeDefinition(ResType type, int id, yy::location loc);
 
-	void addResource(ResSpec spec, CompoundExprPtr body);
-	void addData(ResSpec spec, const std::string& data);
+	void addResource(ResSpec spec, CompoundExprPtr body, yy::location loc);
+	void addData(ResSpec spec, const std::string& data, yy::location loc);
 
 	Resources& getResources() { return resources; }
 
 	bool verboseFlag;
+
+	void problem(Diagnostic d);
 };