Fix typo of register -> registers crashes DXC with segfault (#7729)

Fix crash when parsing mistyped HLSL semantics (e.g. `registers()`).
Add diagnostic for unexpected '(' in semantic annotation and skip safely.
Add tests for common misspellings/macros that previously caused a segfault.
Fixes #6599

Author: Nielsbishere

tools/clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -1025,6 +1025,8 @@ def warn_hlsl_effect_technique : Warning <
 def warn_hlsl_semantic_identifier_collision : Warning <
   "'%0' interpreted as semantic; previous definition(s) ignored">,
   InGroup< HLSLSemanticIdentifierCollision >;
+def err_hlsl_expected_hlsl_attribute : Error <
+  "Unexpected '(' in semantic annotation. Did you mean 'packoffset()' or 'register()'?">;
 def err_hlsl_enum : Error<
   "enum is unsupported in HLSL before 2017">;
 def warn_hlsl_new_feature : Warning <

tools/clang/lib/Parse/ParseDecl.cpp

@@ -633,6 +633,16 @@ bool Parser::MaybeParseHLSLAttributes(std::vector<hlsl::UnusualAnnotation *> &ta
       Actions.DiagnoseSemanticDecl(pUA);
       ConsumeToken(); // consume semantic
 
+      // Likely a misspell of register(), packoffset() or a mismatching macro:
+      // both registr() and packofset() would cause a crash without this fix.
+
+      if (Tok.is(tok::l_paren)) {
+        Diag(Tok.getLocation(), diag::err_hlsl_expected_hlsl_attribute);
+        ConsumeParen();
+        SkipUntil(tok::r_paren, StopAtSemi); // skip through )
+        return true;
+      }
+
       target.push_back(pUA);
     }
     else {

tools/clang/test/SemaHLSL/hlsl-attribute-mistype-errors.hlsl

@@ -0,0 +1,38 @@
+// RUN: %dxc -T lib_6_3 -verify %s
+
+// expected-error@+1 {{Unexpected '(' in semantic annotation. Did you mean 'packoffset()' or 'register()'?}}
+RWStructuredBuffer<float4> uav1 : registers(u3);
+
+// expected-error@+1 {{Unexpected '(' in semantic annotation. Did you mean 'packoffset()' or 'register()'?}}
+RWStructuredBuffer<float4> uav2 : registers(outer_space);
+
+// expected-error@+1 {{Unexpected '(' in semantic annotation. Did you mean 'packoffset()' or 'register()'?}}
+RWStructuredBuffer<float4> uav3 : UNDEFINED_MACRO1(u3);
+
+// expected-error@+1 {{Unexpected '(' in semantic annotation. Did you mean 'packoffset()' or 'register()'?}}
+RWStructuredBuffer<float4> uav4 : UNDEFINED_MACRO(something, more, complex);
+
+cbuffer buf {
+
+  // expected-error@+1 {{Unexpected '(' in semantic annotation. Did you mean 'packoffset()' or 'register()'?}}
+  float4 v0 : packoffsets(c0);
+
+  // expected-error@+1 {{Unexpected '(' in semantic annotation. Did you mean 'packoffset()' or 'register()'?}}
+  float4 v1 : packoffsets(invalid_syntax);
+
+  // expected-error@+1 {{Unexpected '(' in semantic annotation. Did you mean 'packoffset()' or 'register()'?}}
+  float v2 : UNDEFINED_MACRO2(c0.w);
+
+  // expected-error@+1 {{Unexpected '(' in semantic annotation. Did you mean 'packoffset()' or 'register()'?}}
+  float v3 : UNDEFINED_MACRO(something, more, complex);
+};
+
+[shader("pixel")]
+float4 main(): SV_Target
+{
+  uav1[0] = v0;
+  uav2[0] = v1;
+  uav3[0] = v2;
+  uav4[0] = v3;
+  return 0.xxxx;
+}