From ff3b43b6c15c3331d156b147b559892ee7ccdacb Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 13 Mar 2021 16:22:43 +0200
Subject: [PATCH] Better error message for the subscript operator

---
 source/glsl/validate.cpp          | 10 ++++++++--
 tests/glsl/invalid_subscript.glsl | 13 +++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)
 create mode 100644 tests/glsl/invalid_subscript.glsl

diff --git a/source/glsl/validate.cpp b/source/glsl/validate.cpp
index 13cb5ccb..4b38c5b7 100644
--- a/source/glsl/validate.cpp
+++ b/source/glsl/validate.cpp
@@ -338,8 +338,14 @@ void ExpressionValidator::visit(UnaryExpression &unary)
 void ExpressionValidator::visit(BinaryExpression &binary)
 {
 	if(!binary.type && binary.left->type && binary.right->type)
-		error(binary, format("No matching operator '%s' found for '%s' and '%s'",
-			binary.oper->token, binary.left->type->name, binary.right->type->name));
+	{
+		if(binary.oper->token[0]=='[')
+			error(binary, format("Can't index element of '%s' with '%s'",
+				binary.left->type->name, binary.right->type->name));
+		else
+			error(binary, format("No matching operator '%s' found for '%s' and '%s'",
+				binary.oper->token, binary.left->type->name, binary.right->type->name));
+	}
 	TraversingVisitor::visit(binary);
 }
 
diff --git a/tests/glsl/invalid_subscript.glsl b/tests/glsl/invalid_subscript.glsl
new file mode 100644
index 00000000..6826feff
--- /dev/null
+++ b/tests/glsl/invalid_subscript.glsl
@@ -0,0 +1,13 @@
+#pragma MSP stage(vertex)
+layout(location=0) in vec4 position;
+layout(location=1) in float scale;
+int main()
+{
+	gl_Position = position[scale];
+	gl_Position = scale[position];
+}
+
+/* Expected error:
+<test>:6: Can't index element of 'vec4' with 'float'
+<test>:7: Can't index element of 'float' with 'vec4'
+*/
-- 
2.43.0