[CSGen] Don't merge type variables for literals in computeFavoredTypeForExpr

Author: hborla

lib/Sema/CSGen.cpp

@@ -339,22 +339,6 @@ namespace {
 
     expr->walk(LinkedExprAnalyzer(lti, CS));
 
-    auto mergeTypeVariables = [&](ArrayRef<TypeVariableType *> typeVars) {
-      if (typeVars.size() < 2)
-        return;
-
-      auto rep1 = CS.getRepresentative(typeVars.front());
-      for (unsigned i = 1, n = typeVars.size(); i != n; ++i) {
-        auto rep2 = CS.getRepresentative(typeVars[i]);
-        if (rep1 != rep2)
-          CS.mergeEquivalenceClasses(rep1, rep2, /*updateWorkList*/ false);
-      }
-    };
-
-    mergeTypeVariables(lti.intLiteralTyvars);
-    mergeTypeVariables(lti.floatLiteralTyvars);
-    mergeTypeVariables(lti.stringLiteralTyvars);
-
     if (lti.collectedTypes.size() == 1) {
       // TODO: Compute the BCT.
 

test/stdlib/UnicodeScalarDiagnostics.swift

@@ -8,9 +8,9 @@ func isString(_ s: inout String) {}
 func test_UnicodeScalarDoesNotImplementArithmetic(_ us: UnicodeScalar, i: Int) {
   var a1 = "a" + "b" // OK
   isString(&a1)
-  let a2 = "a" - "b" // expected-error {{binary operator '-' cannot be applied to two 'String' operands}}
-  let a3 = "a" * "b" // expected-error {{binary operator '*' cannot be applied to two 'String' operands}}
-  let a4 = "a" / "b" // expected-error {{binary operator '/' cannot be applied to two 'String' operands}}
+  let a2 = "a" - "b" // expected-error {{binary operator '-' cannot be applied to two 'String' operands}} expected-note {{}}
+  let a3 = "a" * "b" // expected-error {{binary operator '*' cannot be applied to two 'String' operands}} expected-note {{}}
+  let a4 = "a" / "b" // expected-error {{binary operator '/' cannot be applied to two 'String' operands}} expected-note {{}}
 
   let b1 = us + us // expected-error {{binary operator '+' cannot be applied to two 'UnicodeScalar' (aka 'Unicode.Scalar') operands}}
   let b2 = us - us // expected-error {{binary operator '-' cannot be applied to two 'UnicodeScalar' (aka 'Unicode.Scalar') operands}}