From 17e3b88b541ed7f45d575f0f9caaa808cd0a6619 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Wed, 1 Jun 2022 17:37:07 -0700
Subject: New language feature: basic error handling. (#2253)

* New language feature: basic error handling.

* Fix.

* Fix `tryCall` encoding according to code review.

Co-authored-by: Yong He <yhe@nvidia.com>
---
 source/slang/slang-check-expr.cpp | 62 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

(limited to 'source/slang/slang-check-expr.cpp')

diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 317ab6a1a..4b29de1bf 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -1337,6 +1337,15 @@ namespace Slang
             // if this is still an invoke expression, test arguments passed to inout/out parameter are LValues
             if(auto funcType = as<FuncType>(invoke->functionExpr->type))
             {
+                if (!funcType->errorType->equals(m_astBuilder->getVoidType()))
+                {
+                    // If the callee throws, make sure we are inside a try clause.
+                    if (m_enclosingTryClauseType == TryClauseType::None)
+                    {
+                        getSink()->diagnose(invoke, Diagnostics::mustUseTryClauseToCallAThrowFunc);
+                    }
+                }
+
                 Index paramCount = funcType->getParamCount();
                 for (Index pp = 0; pp < paramCount; ++pp)
                 {
@@ -1529,6 +1538,59 @@ namespace Slang
         return CheckInvokeExprWithCheckedOperands(expr);
     }
 
+    Expr* SemanticsExprVisitor::visitTryExpr(TryExpr* expr)
+    {
+        auto prevTryClauseType = expr->tryClauseType;
+        m_enclosingTryClauseType = expr->tryClauseType;
+        expr->base = CheckTerm(expr->base);
+        m_enclosingTryClauseType = prevTryClauseType;
+        expr->type = expr->base->type;
+        if (as<ErrorType>(expr->type))
+            return expr;
+        
+        auto parentFunc = this->m_parentFunc;
+        // TODO: check if the try clause is caught.
+        // For now we assume all `try`s are not caught (because we don't have catch yet).
+        if (!parentFunc)
+        {
+            getSink()->diagnose(expr, Diagnostics::uncaughtTryCallInNonThrowFunc);
+            return expr;
+        }
+        if (parentFunc->errorType->equals(m_astBuilder->getVoidType()))
+        {
+            getSink()->diagnose(expr, Diagnostics::uncaughtTryCallInNonThrowFunc);
+            return expr;
+        }
+        if (!as<InvokeExpr>(expr->base))
+        {
+            getSink()->diagnose(expr, Diagnostics::tryClauseMustApplyToInvokeExpr);
+            return expr;
+        }
+        auto base = as<InvokeExpr>(expr->base);
+        if (auto callee = as<DeclRefExpr>(base->functionExpr))
+        {
+            if (auto funcCallee = as<FuncDecl>(callee->declRef.getDecl()))
+            {
+                if (funcCallee->errorType->equals(m_astBuilder->getVoidType()))
+                {
+                    getSink()->diagnose(expr, Diagnostics::tryInvokeCalleeShouldThrow, callee->declRef);
+                }
+                if (!parentFunc->errorType->equals(funcCallee->errorType))
+                {
+                    getSink()->diagnose(
+                        expr,
+                        Diagnostics::errorTypeOfCalleeIncompatibleWithCaller,
+                        callee->declRef,
+                        funcCallee->errorType,
+                        parentFunc->errorType);
+                }
+                return expr;
+            }
+        }
+        getSink()->diagnose(expr, Diagnostics::calleeOfTryCallMustBeFunc);
+        return expr;
+    }
+
     Expr* SemanticsVisitor::MaybeDereference(Expr* inExpr)
     {
         Expr* expr = inExpr;
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