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, 11 insertions, 0 deletions

diff --git a/source/slang/slang-language-server-ast-lookup.cpp b/source/slang/slang-language-server-ast-lookup.cpp
index b08388aee..d0ed9cdac 100644
--- a/source/slang/slang-language-server-ast-lookup.cpp
+++ b/source/slang/slang-language-server-ast-lookup.cpp
@@ -645,6 +645,17 @@ struct ASTLookupStmtVisitor : public StmtVisitor<ASTLookupStmtVisitor, bool>
 
     bool visitDeferStmt(DeferStmt* stmt) { return dispatchIfNotNull(stmt->statement); }
 
+    bool visitThrowStmt(ThrowStmt* stmt) { return checkExpr(stmt->expression); }
+
+    bool visitCatchStmt(CatchStmt* stmt)
+    {
+        if (stmt->errorVar && _findAstNodeImpl(*context, stmt->errorVar))
+            return true;
+        if (dispatchIfNotNull(stmt->tryBody))
+            return true;
+        return dispatchIfNotNull(stmt->handleBody);
+    }
+
     bool visitWhileStmt(WhileStmt* stmt)
     {
         if (checkExpr(stmt->predicate))