A test I haven't made work, Cost branch

Analysis/src/Linter.cpp

@@ -203,6 +203,24 @@ static bool similar(AstExpr* lhs, AstExpr* rhs)
         return true;
     }
     CASE(AstExprIfElse) return similar(le->condition, re->condition) && similar(le->trueExpr, re->trueExpr) && similar(le->falseExpr, re->falseExpr);
+    CASE(AstExprInterpString)
+    {
+        if (le->strings.size != re->strings.size)
+            return false;
+
+        if (le->expressions.size != re->expressions.size)
+            return false;
+
+        for (size_t i = 0; i < le->strings.size; ++i)
+            if (le->strings.data[i].size != re->strings.data[i].size || memcmp(le->strings.data[i].data, re->strings.data[i].data, le->strings.data[i].size) != 0)
+                return false;
+
+        for (size_t i = 0; i < le->expressions.size; ++i)
+            if (!similar(le->expressions.data[i], re->expressions.data[i]))
+                return false;
+
+        return true;
+    }
     else
     {
         LUAU_ASSERT(!"Unknown expression type");

Compiler/src/CostModel.cpp

@@ -217,6 +217,15 @@ struct CostVisitor : AstVisitor
         {
             return model(expr->condition) + model(expr->trueExpr) + model(expr->falseExpr) + 2;
         }
+        else if (AstExprInterpString* expr = node->as<AstExprInterpString>())
+        {
+            Cost cost = 0;
+
+            for (auto innerExpression : expr->expressions)
+                cost += model(innerExpression);
+
+            return cost;
+        }
         else
         {
             LUAU_ASSERT(!"Unknown expression type");

tests/Conformance.test.cpp

@@ -296,6 +296,7 @@ TEST_CASE("Strings")
 
 TEST_CASE("StringInterp")
 {
+    ScopedFastFlag sff{"LuauInterpolatedStringBaseSupport", true};
     runConformance("stringinterp.lua");
 }
 

tests/Linter.test.cpp

@@ -1662,7 +1662,7 @@ TEST_CASE_FIXTURE(Fixture, "WrongCommentOptimize")
 {
     LintResult result = lint(R"(
 --!optimize
---!optimize   
+--!optimize
 --!optimize me
 --!optimize 100500
 --!optimize 2
@@ -1675,4 +1675,15 @@ TEST_CASE_FIXTURE(Fixture, "WrongCommentOptimize")
     CHECK_EQ(result.warnings[3].text, "optimize directive uses unknown optimization level '100500', 0..2 expected");
 }
 
+TEST_CASE_FIXTURE(Fixture, "TestStringInterpolation")
+{
+    ScopedFastFlag sff{"LuauInterpolatedStringBaseSupport", true};
+
+    LintResult result = lint(R"(
+        local _ = `unknown {foo}`
+    )");
+
+    REQUIRE_EQ(result.warnings.size(), 1);
+}
+
 TEST_SUITE_END();