Fix erroneous error claiming variable is being used before its declaration (#2958)

* Simplify type of diagnoseImpl

* Show source line for Note diagnostics, opting out of this where appropriate

* Make declared after use diagnostic clearer

* Fix erroneous error claiming variable is being used before its declaration

Closes https://github.com/shader-slang/slang/issues/2936

* Fix build on msvc

---------

Co-authored-by: jsmall-nvidia <jsmall@nvidia.com>

2 files changed, 59 insertions, 0 deletions

diff --git a/tests/bugs/generic-type-arg-overloaded.slang.expected b/tests/bugs/generic-type-arg-overloaded.slang.expected
index 390c4fe00..1c41da717 100644
--- a/tests/bugs/generic-type-arg-overloaded.slang.expected
+++ b/tests/bugs/generic-type-arg-overloaded.slang.expected
@@ -4,11 +4,17 @@ tests/bugs/generic-type-arg-overloaded.slang(14): error 30200: declaration of 'S
 struct Stuff {}
        ^~~~~
 tests/bugs/generic-type-arg-overloaded.slang(11): note: see previous declaration of 'Stuff'
+struct Stuff : IThing { int getVal() { return 1; } }
+       ^~~~~
 tests/bugs/generic-type-arg-overloaded.slang(26): error 39999: ambiguous reference to 'Stuff'
     return util<Stuff>()
                 ^~~~~
 tests/bugs/generic-type-arg-overloaded.slang(14): note 39999: candidate: struct Stuff
+struct Stuff {}
+       ^~~~~
 tests/bugs/generic-type-arg-overloaded.slang(11): note 39999: candidate: struct Stuff
+struct Stuff : IThing { int getVal() { return 1; } }
+       ^~~~~
 tests/bugs/generic-type-arg-overloaded.slang(32): error 39999: expected a generic when using '<...>' (found: '() -> int')
         + nonGeneric<G>();
           ^~~~~~~~~~
diff --git a/tests/bugs/gh-2936.slang b/tests/bugs/gh-2936.slang
new file mode 100644
index 000000000..20bfa1924
--- /dev/null
+++ b/tests/bugs/gh-2936.slang
@@ -0,0 +1,53 @@
+//TEST(smoke,compute):COMPARE_COMPUTE(filecheck-buffer=CHECK):-cpu -shaderobj -output-using-type
+
+// CHECK:        4
+// CHECK-NEXT:  99
+// CHECK-NEXT: 111
+// CHECK-NEXT:  40
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+[numthreads(1, 1, 1)]
+void computeMain()
+{
+    outputBuffer[0] = f();
+    outputBuffer[1] = g();
+    outputBuffer[2] = h();
+    outputBuffer[3] = k(30, 40);
+}
+
+static let x = 1;
+
+func f() -> int
+{
+    let y = x; // should refer to the global x
+    let x = 3;
+    return x + y; // should refer to the local x
+}
+func g() -> int
+{
+    // Can we shadow this keyword
+    int out;
+    out = 99;
+    return out;
+}
+
+static var input = 999;
+func h() -> int
+{
+    // This should still parse as an identifier (it's a keyword, being shadowed
+    // by something in a parent scope)
+    input = 10;
+    int input = input;
+    input += 101;
+    return input;
+}
+
+int k(int a, int b)
+{
+    int umax = max(a, b);
+
+    int max = umax;
+    return max;
+}