Static casts should only propagate wider types

MikePopoloski · Jan 14, 2025 · 98c2035 · 98c2035
1 parent 06b1a76
commit 98c2035
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Showing 2 changed files with 20 additions and 3 deletions.
diff --git a/source/ast/expressions/ConversionExpression.cpp b/source/ast/expressions/ConversionExpression.cpp
@@ -413,9 +413,9 @@ Expression& ConversionExpression::fromSyntax(Compilation& comp, const CastExpres
         // The type we propagate should use the sign of the operand, just like it
         // would if we were doing an implicit conversion via an assignment expression.
         auto propagatedType = type;
-        if (type->isIntegral() && operand->type->isIntegral() &&
-            type->getIntegralFlags() != operand->type->getIntegralFlags()) {
-            propagatedType = &comp.getType(type->getBitWidth(), operand->type->getIntegralFlags());
+        if (type->isNumeric() && operand->type->isNumeric()) {
+            propagatedType = OpInfo::binaryType(comp, type, operand->type, false,
+                                                /* signednessFromRt */ true);
         }
 
         contextDetermined(context, operand, nullptr, *propagatedType, syntax.apostrophe.range(),

diff --git a/tests/unittests/ast/ExpressionTests.cpp b/tests/unittests/ast/ExpressionTests.cpp
@@ -3788,3 +3788,20 @@ endmodule
     compilation.addSyntaxTree(tree);
     NO_COMPILATION_ERRORS;
 }
+
+TEST_CASE("Static casts propagate type correctly and don't truncate") {
+    auto tree = SyntaxTree::fromText(R"(
+typedef logic [6:0] lt;
+function automatic logic[7:0] foo;
+    logic [7:0] a = 8'hff;
+    lt b = lt'(a >> 1);
+    return 8'(b);
+endfunction
+
+$static_assert(foo() == 8'h7f);
+)");
+
+    Compilation compilation;
+    compilation.addSyntaxTree(tree);
+    NO_COMPILATION_ERRORS;
+}