[turbofan] Introduce PlainPrimitiveToNumber.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index 80b2b8b806bbb74143e0ab42d46b48aa49bff0ba..6cda67e0d38d4b6a0fbe2e6856a956b2b05cb1cc 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -1759,6 +1759,18 @@ Type* Typer::Visitor::TypeNumberShiftRightLogical(Node* node) {
   return Type::Unsigned32();
 }
 
+Type* Typer::Visitor::TypePlainPrimitiveToNumber(Node* node) {
+  return TypeUnaryOp(node, ToNumber);
+}
+
+Type* Typer::Visitor::TypePlainPrimitiveToWord32(Node* node) {
+  return Type::Integral32();
+}
+
+Type* Typer::Visitor::TypePlainPrimitiveToFloat64(Node* node) {
+  return Type::Number();
+}
+
 Type* Typer::Visitor::TypeNumberImul(Node* node) { return Type::Signed32(); }
 
 Type* Typer::Visitor::TypeNumberClz32(Node* node) {