checker: check generic undefined operation (fix #18162) (#18166)

vlib/v/checker/infix.v

@@ -383,6 +383,10 @@ fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 			}
 		}
 		.gt, .lt, .ge, .le {
+			unwrapped_left_type := c.unwrap_generic(left_type)
+			left_sym = c.table.sym(unwrapped_left_type)
+			unwrapped_right_type := c.unwrap_generic(right_type)
+			right_sym = c.table.sym(unwrapped_right_type)
 			if left_sym.kind in [.array, .array_fixed] && right_sym.kind in [.array, .array_fixed] {
 				c.error('only `==` and `!=` are defined on arrays', node.pos)
 			} else if left_sym.kind == .struct_
@@ -392,8 +396,8 @@ fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 			} else if left_sym.kind == .struct_ && right_sym.kind == .struct_
 				&& node.op in [.eq, .lt] {
 				if !(left_sym.has_method(node.op.str()) && right_sym.has_method(node.op.str())) {
-					left_name := c.table.type_to_str(left_type)
-					right_name := c.table.type_to_str(right_type)
+					left_name := c.table.type_to_str(unwrapped_left_type)
+					right_name := c.table.type_to_str(unwrapped_right_type)
 					if left_name == right_name {
 						if !(node.op == .lt && c.pref.translated) {
 							// Allow `&Foo < &Foo` in translated code.
@@ -670,7 +674,8 @@ fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 				c.error('only `==`, `!=`, `|` and `&` are defined on `[flag]` tagged `enum`, use an explicit cast to `int` if needed',
 					node.pos)
 			}
-		} else if !c.pref.translated && !c.file.is_translated {
+		} else if !c.pref.translated && !c.file.is_translated && !left_type.has_flag(.generic)
+			&& !right_type.has_flag(.generic) {
 			// Regular enums
 			c.error('only `==` and `!=` are defined on `enum`, use an explicit cast to `int` if needed',
 				node.pos)

vlib/v/checker/tests/generics_undefined_operation_2.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/generics_undefined_operation_2.vv:23:18: error: undefined operation `&INode` < `&INode`
+   21 | fn (mut h IHeap[T]) percolateup(hl u64, mut element T) {
+   22 |     mut hole := hl
+   23 |     for hole > 1 && element < h.array[hole / 2] {
+      |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+   24 |         // ^ Notice that '<' was not defined
+   25 |         println("didnt define '<' for the INode")

vlib/v/checker/tests/generics_undefined_operation_2.vv

@@ -0,0 +1,33 @@
+pub struct INode {
+mut:
+	heapindex u64
+}
+
+pub struct IHeap[T] {
+mut:
+	array []&T
+	size  u64
+}
+
+pub fn create_iheap[T](capacity int) &IHeap[T] {
+	mut h := &IHeap[T]{
+		array: []&T{cap: capacity}
+		size: 0
+	}
+	h.array << &T(unsafe { nil })
+	return h
+}
+
+fn (mut h IHeap[T]) percolateup(hl u64, mut element T) {
+	mut hole := hl
+	for hole > 1 && element < h.array[hole / 2] {
+		// ^ Notice that '<' was not defined
+		println("didnt define '<' for the INode")
+		hole /= 2
+	}
+}
+
+fn main() {
+	heap := create_iheap[INode](3000000)
+	println(heap)
+}