Implement throw & catch statements (#6916)

* Implement throw statement

It already existed in the IR, so only parsing, checking and lowering was
missing.

* Initial catch implementation

Likely very broken.

* Error out when catch() isn't last in scope

* Prevent accessing variables from scope preceding catch

As those may actually not be available at that point.

* Add IError and use it in Result type lowering

* Add diagnostic tests

* Allow caught throws in non-throw functions

* Fix catch propagating between functions & SPIR-V merge issue

* Add test for non-trivial error types

* Fix MSVC build

* Fix invalid value type from Result lowering

* Also lower error handling in templates

* Lower result types only after specialization

* Attempt to disambiguate error enums by witness table

* Revert matching by witness, types should be distinct too

* Don't assert valueField when getting Result's error value

It may not exist if the function returns void, but getting the error
value is still legitimate.

* Update tests for new error numbers & get rid of expected.txt

* Change catch lowering to resemble breaking a loop

... To make SPIR-V happy.

* Fix dead catch blocks and invalid cached dominator tree

* More SPIR-V adjustment

* Lower catch as two nested loops

* Add defer interaction test and revert broken defer changes

* Fix enum type when throwing literals

* Cleanup and bikeshedding

* Document error handling mechanism

* Fix table of contents

* Use boolean tag in Result<T, E>

* Use anyValue storage for Result<T,E>

* Remove IError

* Fix formatting

* Eradicate success values from docs and tests

* Use parseModernParamDecl for catch parameter

* Implement do-catch syntax

* Implement catch-all

* Fix formatting

* Fix marshalling native calls that throw

---------

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/source/slang/slang-emit.cpp b/source/slang/slang-emit.cpp
index 260bee0ff..a4362b912 100644
--- a/source/slang/slang-emit.cpp
+++ b/source/slang/slang-emit.cpp
@@ -806,10 +806,6 @@ Result linkAndOptimizeIR(
         break;
     }
 
-    // Lower `Result<T,E>` types into ordinary struct types.
-    if (requiredLoweringPassSet.resultType)
-        lowerResultType(irModule, sink);
-
 #if 0
     dumpIRIfEnabled(codeGenContext, irModule, "UNIONS DESUGARED");
 #endif
@@ -951,6 +947,12 @@ Result linkAndOptimizeIR(
             break;
     }
 
+    // Lower `Result<T,E>` types into ordinary struct types. This must happen
+    // after specialization, since otherwise incompatible copies of the lowered
+    // result structure are generated.
+    if (requiredLoweringPassSet.resultType)
+        lowerResultType(irModule, sink);
+
     // Report checkpointing information
     if (codeGenContext->shouldReportCheckpointIntermediates())
     {