Made sure null_check_test reproduces exact issue.

lang/README.md

@@ -1059,16 +1059,21 @@ main := fn(): uint {
 
 #### null_check_test
 ```hb
-main := fn(): uint {
-	ptr := @as(?^uint, null)
+get_ptr := fn(): ?^uint {
 	value := 0
-	ptr = &value
-
-	if ptr == null {
-		return 1
+	return &value
 }
 
-	return *ptr
+main := fn(): void {
+	ptr := get_ptr()
+
+	if ptr == null {
+		return
+	}
+
+	loop {
+		*ptr += 1
+	}
 }
 ```
 

lang/tests/son_tests_inlining_loops.txt

@@ -0,0 +1,8 @@
+main:
+    LRA r2, r0, :x
+    LI64 r1, 0d
+    ST r1, r2, 0a, 8h
+    JALA r0, r31, 0a
+code size: 57
+ret: 0
+status: Ok(())

lang/tests/son_tests_null_check_test.txt

@@ -0,0 +1,6 @@
+test.hb:15:4: can't prove the value is not 'null', use '@unwrap(<opt>)' if you believe compiler is stupid, or explicitly check for null and handle it ('if <opt> == null { /* handle */ } else { /* use opt */ }')
+        *ptr += 1
+         ^
+test.hb:15:4: can't prove the value is not 'null', use '@unwrap(<opt>)' if you believe compiler is stupid, or explicitly check for null and handle it ('if <opt> == null { /* handle */ } else { /* use opt */ }')
+        *ptr += 1
+         ^