Disallow swizzling on long vectors (#7215)

This PR addresses
#7194 by adding
a new error string in DiagnosticSemaKinds.td and emitting it in
SemaHLSL.cpp.

@pow2clk implemented most of this in his
[fork](a41e0a6).
I'm just helping to finish it.

**How verified:**
1. Several new test cases were added and verified locally
2. Ran hcttest locally

Author: alsepkow

tools/clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -7549,6 +7549,8 @@ def err_hlsl_vector_element_index_out_of_bounds: Error<
   "vector element index '%0' is out of bounds">;
 def err_hlsl_vector_member_too_many_positions: Error<
   "more than four positions are referenced in '%0'">;
+def err_hlsl_vector_member_on_long_vector: Error<
+   "invalid swizzle '%0' on vector of over 4 elements.">;
 def err_hlsl_missing_type_specifier : Error< // Patterened after err_missing_type_specifier
   "HLSL requires a type specifier for all declarations">;
 def err_hlsl_multiple_concrete_bases : Error<

tools/clang/lib/Sema/SemaHLSL.cpp

@@ -8643,6 +8643,9 @@ ExprResult HLSLExternalSource::LookupVectorMemberExprForHLSL(
     llvm_unreachable("Unknown VectorMemberAccessError value");
   }
 
+  if (colCount > 4)
+    msg = diag::err_hlsl_vector_member_on_long_vector;
+
   if (msg != 0) {
     m_sema->Diag(MemberLoc, msg) << memberText;
 

tools/clang/test/SemaHLSL/hlsl/types/invalid-longvec-swizzle.hlsl

@@ -0,0 +1,27 @@
+// RUN: %dxc -Tlib_6_9 -verify %s -DTYPE=float
+// RUN: %dxc -Tlib_6_9 -verify %s -DTYPE=bool
+// RUN: %dxc -Tlib_6_9 -verify %s -DTYPE=uint64_t
+// RUN: %dxc -Tlib_6_9 -verify %s -DTYPE=double
+// RUN: %dxc -Tlib_6_9 -verify %s -enable-16bit-types -DTYPE=float16_t
+// RUN: %dxc -Tlib_6_9 -verify %s -enable-16bit-types -DTYPE=int16_t
+
+export
+vector<double, 3> doit(vector<double, 5> vec5) {
+  vec5.x = 1; // expected-error {{invalid swizzle 'x' on vector of over 4 elements.}}
+  return vec5.xyw; // expected-error {{invalid swizzle 'xyw' on vector of over 4 elements.}}
+}
+
+export
+TYPE arr_to_vec(TYPE arr[5]) {
+
+  TYPE val = (vector<TYPE, 6>(arr, 1)).x; // expected-error {{invalid swizzle 'x' on vector of over 4 elements.}}
+
+  TYPE val2 = ((vector<TYPE, 5>)arr).x; // expected-error {{invalid swizzle 'x' on vector of over 4 elements.}}
+
+  return val;
+}
+
+export TYPE lv_ctor(TYPE s) {
+  TYPE ret = (vector<TYPE,6>(1, 2, 3, 4, 5, s)).x; // expected-error {{invalid swizzle 'x' on vector of over 4 elements.}}
+  return ret;
+}