@@ -1952,6 +1952,51 @@ namespace Slang
19521952 return checkedExpr;
19531953 }
19541954
1955+ static bool _canLValueCoerceScalarType (Type* a, Type* b)
1956+ {
1957+ auto basicTypeA = as<BasicExpressionType>(a);
1958+ auto basicTypeB = as<BasicExpressionType>(b);
1959+
1960+ if (basicTypeA && basicTypeB)
1961+ {
1962+ const auto & infoA = BaseTypeInfo::getInfo (basicTypeA->baseType );
1963+ const auto & infoB = BaseTypeInfo::getInfo (basicTypeB->baseType );
1964+
1965+ // TODO(JS): Initially this tries to limit where LValueImplict casts happen.
1966+ // We could in principal allow different sizes, as long as we converted to a temprorary
1967+ // and back again.
1968+ //
1969+ // For now we just stick with the simple case.
1970+ // // We only allow on integer types for now. In effect just allowing any size uint/int conversions
1971+ if (infoA.sizeInBytes == infoB.sizeInBytes &&
1972+ (infoA.flags & infoB.flags & BaseTypeInfo::Flag::Integer))
1973+ {
1974+ return true ;
1975+ }
1976+
1977+ }
1978+ return false ;
1979+ }
1980+
1981+ static bool _canLValueCoerce (Type* a, Type* b)
1982+ {
1983+ // We can *assume* here that if they are coercable, that dimensions of vectors
1984+ // and matrices match. We might want to assert to be sure...
1985+ SLANG_ASSERT (a != b);
1986+ if (a->astNodeType == b->astNodeType )
1987+ {
1988+ if (auto matA = as<MatrixExpressionType>(a))
1989+ {
1990+ return _canLValueCoerceScalarType (matA->getElementType (), static_cast <MatrixExpressionType*>(b)->getElementType ());
1991+ }
1992+ else if (auto vecA = as<VectorExpressionType>(a))
1993+ {
1994+ return _canLValueCoerceScalarType (vecA->getScalarType (), static_cast <VectorExpressionType*>(b)->getScalarType ());
1995+ }
1996+ }
1997+ return _canLValueCoerceScalarType (a, b);
1998+ }
1999+
19552000 Expr* SemanticsVisitor::CheckInvokeExprWithCheckedOperands (InvokeExpr *expr)
19562001 {
19572002 auto rs = ResolveInvoke (expr);
@@ -1985,23 +2030,63 @@ namespace Slang
19852030 if ( pp < expr->arguments .getCount () )
19862031 {
19872032 auto argExpr = expr->arguments [pp];
1988- if ( !argExpr->type .isLeftValue )
2033+ if ( !argExpr->type .isLeftValue )
19892034 {
1990- getSink ()->diagnose (
1991- argExpr,
1992- Diagnostics::argumentExpectedLValue,
1993- pp);
2035+ auto implicitCastExpr = as<ImplicitCastExpr>(argExpr);
19942036
1995- if ( auto implicitCastExpr = as<ImplicitCastExpr>(argExpr) )
2037+ if (implicitCastExpr && _canLValueCoerce (implicitCastExpr->arguments [0 ]->type , implicitCastExpr->type ))
2038+ {
2039+ // This is to work around issues like
2040+ //
2041+ // ```
2042+ // int a = 0;
2043+ // uint b = 1;
2044+ // a += b;
2045+ // ```
2046+ // That strictly speaking it's not allowed, but we are going to allow it for now
2047+ // for situations were the types are uint/int and vector/matrix varieties of those types
2048+ //
2049+ // Then in lowering we are going to insert code to do something like
2050+ // ```
2051+ // var OutType: tmp = arg;
2052+ // f(... tmp);
2053+ // arg = tmp;
2054+ // ```
2055+
2056+ TypeCastExpr* lValueImplicitCast;
2057+
2058+ // We want to record if the cast is being used for `out` or `inout`/`ref` as
2059+ // if it's just `out` we won't need to convert before passing in.
2060+ if (as<OutType>(paramType))
2061+ {
2062+ lValueImplicitCast = getASTBuilder ()->create <OutImplicitCastExpr>(*implicitCastExpr);
2063+ }
2064+ else
2065+ {
2066+ lValueImplicitCast = getASTBuilder ()->create <InOutImplicitCastExpr>(*implicitCastExpr);
2067+ }
2068+
2069+ // Replace the expression. This should make this situation easier to detect.
2070+ expr->arguments [pp] = lValueImplicitCast;
2071+ }
2072+ else
19962073 {
19972074 getSink ()->diagnose (
19982075 argExpr,
1999- Diagnostics::implicitCastUsedAsLValue,
2000- implicitCastExpr->arguments [0 ]->type ,
2001- implicitCastExpr->type );
2076+ Diagnostics::argumentExpectedLValue,
2077+ pp);
2078+
2079+ if (implicitCastExpr)
2080+ {
2081+ getSink ()->diagnose (
2082+ argExpr,
2083+ Diagnostics::implicitCastUsedAsLValue,
2084+ implicitCastExpr->arguments [pp]->type ,
2085+ implicitCastExpr->type );
2086+ }
2087+
2088+ maybeDiagnoseThisNotLValue (argExpr);
20022089 }
2003-
2004- maybeDiagnoseThisNotLValue (argExpr);
20052090 }
20062091 }
20072092 else
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