Merge from 0.9.x (#429)

* Fix bug when subscripting a type that must be split (#396)

The logic was creating a `PairPseudoExpr` as part of a subscript (`operator[]`) operation, but neglecting to fill in its `pairInfo` field, which led to a null-pointer crash further along.

* Allow writes to UAV textures (#416)

Work on #415

This issue is already fixed in the `v0.10.*` line, but I'm back-porting the fix to `v0.9.*`.
The issue here was that the stdlib declarations for texture types were only including the `get` accessor for subscript operations, even if the texture was write-able.

I've also included the fixes for other subscript accessors in the stdlib (notably that `OutputPatch<T>` is readable, but not writable, despite what the name seems to imply).

* Fix infinite loop in semantic parsing (#424)

The code for parsing semantics was looking for a fixed set of tokens to terminate a semantic list, rather than assuming that whenever you don't see a `:` ahead, you probably are done with semantics. This meant that you could get into an infinite loop just with simple mistakes like leaving out a `;`.

This change fixes the parser to note infinite loop in this case, and adds a test case to verify the fix.

4 files changed, 59 insertions, 12 deletions

diff --git a/source/slang/parser.cpp b/source/slang/parser.cpp
index 037268244..82f79af17 100644
--- a/source/slang/parser.cpp
+++ b/source/slang/parser.cpp
@@ -1863,12 +1863,18 @@ namespace Slang
             ParseHLSLLayoutSemantic(parser, semantic.Ptr());
             return semantic;
         }
-        else
+        else if (parser->LookAheadToken(TokenType::Identifier))
         {
             RefPtr<HLSLSimpleSemantic> semantic = new HLSLSimpleSemantic();
             semantic->name = parser->ReadToken(TokenType::Identifier);
             return semantic;
         }
+        else
+        {
+            // expect an identifier, just to produce an error message
+            parser->ReadToken(TokenType::Identifier);
+            return nullptr;
+        }
     }
 
     //
@@ -1893,20 +1899,26 @@ namespace Slang
                 link = &semantic->next;
             }
 
-            switch (parser->tokenReader.PeekTokenType())
+            // If we see another `:`, then that means there
+            // is yet another semantic to be processed.
+            // Otherwise we assume we are at the end of the list.
+            //
+            // TODO: This could produce sub-optimal diagnostics
+            // when the user *meant* to apply multiple semantics
+            // to a single declaration:
+            //
+            //     Foo foo : register(t0)   register(s0);
+            //                            ^
+            //         missing ':' here   |
+            //
+            // However, that is an uncommon occurence, and trying
+            // to continue parsing semantics here even if we didn't
+            // see a colon forces us to be careful about 
+            // avoiding an infinite loop here.
+            if (!AdvanceIf(parser, TokenType::Colon))
             {
-            case TokenType::LBrace:
-            case TokenType::Semicolon:
-            case TokenType::Comma:
-            case TokenType::RParent:
-            case TokenType::EndOfFile:
                 return result;
-
-            default:
-                break;
             }
-
-            parser->ReadToken(TokenType::Colon);
         }
 
     }
diff --git a/tests/diagnostics/missing-semicolon-after-semantic.slang b/tests/diagnostics/missing-semicolon-after-semantic.slang
new file mode 100644
index 000000000..00fc3aa6c
--- /dev/null
+++ b/tests/diagnostics/missing-semicolon-after-semantic.slang
@@ -0,0 +1,9 @@
+//TEST:SIMPLE:
+
+// Forgetting to put in the `;` after declaraing a variable/field
+// with a semantic used to put the compiler into an infinite loop.
+
+struct Test
+{
+	float4 pos : SV_POSITION
+};
diff --git a/tests/diagnostics/missing-semicolon-after-semantic.slang.expected b/tests/diagnostics/missing-semicolon-after-semantic.slang.expected
new file mode 100644
index 000000000..ae82385d0
--- /dev/null
+++ b/tests/diagnostics/missing-semicolon-after-semantic.slang.expected
@@ -0,0 +1,6 @@
+result code = -1
+standard error = {
+tests/diagnostics/missing-semicolon-after-semantic.slang(9): error 20001: unexpected '}', expected ';'
+}
+standard output = {
+}
diff --git a/tests/front-end/uav-write.slang b/tests/front-end/uav-write.slang
new file mode 100644
index 000000000..c70af26a3
--- /dev/null
+++ b/tests/front-end/uav-write.slang
@@ -0,0 +1,20 @@
+// uav-write.slang
+//TEST:SIMPLE:
+
+// Just confirming that code that writes to a UAV will type-check.
+
+RWTexture2D<float4> gOutput;
+
+float4 test(uint2 coord, float4 value)
+{
+	// read
+    value = value + gOutput[coord];
+
+    // write
+    gOutput[coord] = value;
+
+    // read-modify-write
+    gOutput[coord] += value;
+	
+	return value;
+}
\ No newline at end of file