From 8212a66ff27e56531e0b48807088f1c544d75756 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Mon, 28 Sep 2026 09:23:27 -0700
Subject: Check un-init not-null constructor fields

Propagate BOT inputs; Arith, Load.
CallEnd inlining, the FUnPtr dies early.
Load asserts when loading against uninit not-null field.
Keep not-nill state for storage class.
Clean up Node.peep as constant.
---
 .../src/main/java/com/seaofnodes/simple/node/LoadNode.java  |  1 +
 .../src/main/java/com/seaofnodes/simple/node/StoreNode.java |  2 ++
 .../src/test/java/com/seaofnodes/simple/Chapter10Test.java  |  6 +++++-
 .../src/test/java/com/seaofnodes/simple/Chapter16Test.java  | 13 +++++--------
 4 files changed, 13 insertions(+), 9 deletions(-)

(limited to 'chapter22/src')

diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/LoadNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/LoadNode.java
index 4f09400a..e0a6d09a 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/LoadNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/LoadNode.java
@@ -145,6 +145,7 @@ public class LoadNode extends MemOpNode {
     private Node zero(NewNode nnn) {
         TypeStruct ts = nnn._ptr._obj;
         Type zero = ts._fields[ts.findAlias(_alias)]._type.makeZero();
+        assert zero.isa(_type); // Catch an uninitialized non-null field
         return castRO(new ConstantNode(zero).peephole());
     }
 
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/StoreNode.java b/chapter22/src/main/java/com/seaofnodes/simple/node/StoreNode.java
index ce989826..e151911c 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/StoreNode.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/StoreNode.java
@@ -123,6 +123,8 @@ public class StoreNode extends MemOpNode {
     public Parser.ParseException err() {
         Parser.ParseException err = super.err();
         if( err != null ) return err;
+        if( ptr()._type == Type.TOP )
+            return null; // Dead store
         TypeMemPtr tmp = (TypeMemPtr)ptr()._type;
         if( tmp._obj.field(_name)._final && !_init )
             return Parser.error("Cannot modify final field '"+_name+"'",_loc);
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter10Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter10Test.java
index 9b5d5da6..aa2cd941 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter10Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter10Test.java
@@ -47,6 +47,7 @@ public class Chapter10Test {
     public void testNullGuardErrors() {
         for( String body : new String[] {
             "return p.x;",
+            "if (p == null) return p.x; return -1;",
             "if (!!points) return p.x; return -1;",
             "if (!!p) { int x = p.x; } return p.x;"
         } ) {
@@ -54,7 +55,10 @@ public class Chapter10Test {
                 new CodeGen(NULLABLE_POINT_SOURCE+body).parse().opto().typeCheck();
                 fail(body);
             } catch( RuntimeException e ) {
-                assertEquals(body,"Might be null accessing 'x'",e.getMessage());
+                // Known null is rejected during parsing in these chapters.
+                String expected = body.startsWith("if (p == null)")
+                    ? "Accessing unknown field 'x' from 'null'" : "Might be null accessing 'x'";
+                assertEquals(body,expected,e.getMessage());
             }
         }
     }
diff --git a/chapter22/src/test/java/com/seaofnodes/simple/Chapter16Test.java b/chapter22/src/test/java/com/seaofnodes/simple/Chapter16Test.java
index 58bb4148..e7163075 100644
--- a/chapter22/src/test/java/com/seaofnodes/simple/Chapter16Test.java
+++ b/chapter22/src/test/java/com/seaofnodes/simple/Chapter16Test.java
@@ -145,14 +145,11 @@ return p;
 
     @Test
     public void testStructFinal3() {
-        CodeGen code = new CodeGen("""
-struct Point { var x; var y; };
-Point p = new Point;
-p.x++;
-return p;
-""");
-        try { code.parse().opto(); fail(); }
-        catch( Exception e ) { assertEquals("'Point' is not fully initialized, field 'x' needs to be set in a constructor",e.getMessage()); }
+        for( String fields : new String[] { "var x; var y;", "int[] x;", "int[] !x;" } ) {
+            String src = "struct Point { "+fields+" }; Point p = new Point; p.x++; return p;";
+            try { new CodeGen(src).parse().opto(); fail(fields); }
+            catch( Exception e ) { assertEquals("'Point' is not fully initialized, field 'x' needs to be set in a constructor",e.getMessage()); }
+        }
     }
 
     @Test
-- 
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