Fix IR emit logic for methods in `struct` types (#791)

There was a bug in the logic for emitting initial IR, such that it was neglecting to emit "methods" (member functions) unless they were also referenced by a non-member (global) function, or were needed to satisfy an interface requirement. This would only matter for `import`ed modules, since for non-`import`ed code, anything relevant would be referenced by the entry point so that the problem would never surface.

This change fixes the underlying problem by adding a step to the IR lowering pass called `ensureAllDeclsRec` that makes sure that not only global-scope declarations, but also anything nested under a `struct` type gets emitted to the initial IR module.

There are also a few unrelated fixes in this PR, which are things I ran into while making the fix:

* Deleted support for the (long gone) `IRDeclRef` type in our `slang.natvis` file

* Added support for visualizing the value of IR string and integer literals when they appear in the debugger

* Fixed IR dumping logic to not skip emitting `struct` and `interface` instructions. Switching those to inherit from `IRType` accidentally affected how they get printed in IR dumps by default.

* Fixed up the IR linking logic so that it correctly takes `[export]` decorations into account, so that an exported definition will always be taken over any other (unless the latter is more specialized for the target). I initially implemented this in an attempt to fix the original issue, but found it wasn't a fix for the root cause. It is still a better approach than what was implemented previously, so I'm leaving it in place.

3 files changed, 40 insertions, 0 deletions

diff --git a/tests/bugs/gl-33-ext.slang b/tests/bugs/gl-33-ext.slang
new file mode 100644
index 000000000..ae70cfaf0
--- /dev/null
+++ b/tests/bugs/gl-33-ext.slang
@@ -0,0 +1,8 @@
+// gl-33-ext.slang
+//TEST_IGNORE_FILE:
+
+struct A
+{
+    int state;
+    [mutating] int next() { return state; }
+};
diff --git a/tests/bugs/gl-33.slang b/tests/bugs/gl-33.slang
new file mode 100644
index 000000000..89cfa0aad
--- /dev/null
+++ b/tests/bugs/gl-33.slang
@@ -0,0 +1,28 @@
+// gl-33.slang
+//TEST(compute):COMPARE_COMPUTE:
+
+// Test for GitLab issue # 33
+
+import gl_33_ext;
+
+typedef A B;
+
+int test(int val)
+{
+    B b = { val };
+    return b.next();
+}
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):dxbinding(0),glbinding(0),out
+RWStructuredBuffer<int> gBuffer;
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    uint tid = dispatchThreadID.x;
+
+    int val = tid;
+    val = test(val);
+
+    gBuffer[tid] = val;
+}
diff --git a/tests/bugs/gl-33.slang.expected.txt b/tests/bugs/gl-33.slang.expected.txt
new file mode 100644
index 000000000..bc856dafa
--- /dev/null
+++ b/tests/bugs/gl-33.slang.expected.txt
@@ -0,0 +1,4 @@
+0
+1
+2
+3