Warnings for uninitialized fields in constructors (#4680)

* Detect uninitialized fields in constructors

* Reachability check for early returns

* Specialized warnings for synthesized default initializers

* Handling quirks with constructors

* Addressing review comments

* Ignore synthesized constructors if they are not used

1 files changed, 108 insertions, 0 deletions

diff --git a/tests/diagnostics/uninitialized-fields.slang b/tests/diagnostics/uninitialized-fields.slang
new file mode 100644
index 000000000..29e065d2b
--- /dev/null
+++ b/tests/diagnostics/uninitialized-fields.slang
@@ -0,0 +1,108 @@
+//TEST:SIMPLE(filecheck=CHK): -target spirv
+
+extern static const int flag;
+
+struct None
+{
+    int a;
+    int b;
+
+    __init()
+    {
+        a = 0;
+        b = 0;
+    }
+}
+
+struct Simple
+{
+    int value;
+    Simple *next;
+
+    __init(int v, Simple* ptr)
+    {
+        value = v;
+        //CHK-DAG: warning 41020: exiting constructor without initializing field 'next'
+    }
+}
+
+struct Conditional
+{
+    int field;
+    int another_field;
+
+    __init()
+    {
+        field = 0;
+        if (flag == 0)
+            //CHK-DAG: warning 41020: exiting constructor without initializing field 'another_field'
+            return;
+
+        another_field = 0;
+    }
+};
+
+struct Partial
+{
+    int inline = 0;
+    int body = 0;
+
+    __init(int x)
+    {
+        body = x;
+    }
+}
+
+// Warnings here should be a bit different
+struct Implicit
+{
+    //CHK-DAG: warning 41021: default initializer for 'Implicit' will not initialize field 'a'
+    int a;
+    int b = 1;
+    //CHK-DAG: warning 41021: default initializer for 'Implicit' will not initialize field 'c'
+    int c;
+    int d = 1 + 1;
+}
+
+int using_implicit(int x)
+{
+    Implicit impl;
+    impl.a = x;
+    return impl.c;
+}
+
+struct UnusedImplicit
+{
+    // Shouldn't warn here, since its never used
+    int a;
+    int b = 1;
+    int c;
+    int d = 1 + 1;
+}
+
+struct Pass
+{
+    int x = 0;
+    int y = 0;
+}
+
+struct Impl
+{
+    float x;
+
+    __init(float val)
+    {
+        x = val;
+    }
+
+    __init()
+    {
+        float val = 2.0;
+
+        // Shouldn't trigger a warning here
+        return Impl(val);
+    }
+}
+
+//CHK-NOT: warning 41020
+//CHK-NOT: warning 41021