From 7e138eca3b6b3adef59c9b065aa0cd06043f3126 Mon Sep 17 00:00:00 2001
From: Windel Bouwman <windel@windel.nl>
Date: Sun, 7 Jul 2019 12:04:43 +0200
Subject: [PATCH] Improve f-string syntax. Fixes #1099

---
 parser/src/python.lalrpop  |  2 +-
 tests/snippets/fstrings.py |  6 ++++++
 vm/src/obj/objbool.rs      | 14 ++++++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/parser/src/python.lalrpop b/parser/src/python.lalrpop
index 60a81e0203..4d92aac28a 100644
--- a/parser/src/python.lalrpop
+++ b/parser/src/python.lalrpop
@@ -19,7 +19,7 @@ grammar;
 pub Top: ast::Top = {
     StartProgram <p:Program> => ast::Top::Program(p),
     StartStatement <s:Statement> => ast::Top::Statement(s),
-    StartExpression <e:Expression> => ast::Top::Expression(e),
+    StartExpression <e:Test> => ast::Top::Expression(e),
 };
 
 Program: ast::Program = {
diff --git a/tests/snippets/fstrings.py b/tests/snippets/fstrings.py
index c76967acb8..445911c687 100644
--- a/tests/snippets/fstrings.py
+++ b/tests/snippets/fstrings.py
@@ -39,3 +39,9 @@ def __str__(self):
 assert f'{v}' == 'foo'
 assert f'{v!r}' == 'bar'
 assert f'{v!s}' == 'baz'
+
+# advanced expressions:
+
+assert f'{True or True}' == 'True'
+assert f'{1 == 1}' == 'True'
+assert f'{"0" if True else "1"}' == '0'
diff --git a/vm/src/obj/objbool.rs b/vm/src/obj/objbool.rs
index f294434b30..1892eafcb7 100644
--- a/vm/src/obj/objbool.rs
+++ b/vm/src/obj/objbool.rs
@@ -5,6 +5,7 @@ use crate::pyobject::{IntoPyObject, PyContext, PyObjectRef, PyResult, TryFromObj
 use crate::vm::VirtualMachine;
 
 use super::objint::PyInt;
+use super::objstr::PyStringRef;
 use super::objtype;
 
 impl IntoPyObject for bool {
@@ -47,6 +48,7 @@ The class bool is a subclass of the class int, and cannot be subclassed.";
     extend_class!(context, bool_type, {
         "__new__" => context.new_rustfunc(bool_new),
         "__repr__" => context.new_rustfunc(bool_repr),
+        "__format__" => context.new_rustfunc(bool_format),
         "__or__" => context.new_rustfunc(bool_or),
         "__ror__" => context.new_rustfunc(bool_ror),
         "__and__" => context.new_rustfunc(bool_and),
@@ -82,6 +84,18 @@ fn bool_repr(vm: &VirtualMachine, args: PyFuncArgs) -> Result<PyObjectRef, PyObj
     Ok(vm.new_str(s))
 }
 
+fn bool_format(
+    obj: PyObjectRef,
+    format_spec: PyStringRef,
+    vm: &VirtualMachine,
+) -> PyResult<PyStringRef> {
+    if format_spec.value.is_empty() {
+        vm.to_str(&obj)
+    } else {
+        Err(vm.new_type_error("unsupported format string passed to bool.__format__".to_string()))
+    }
+}
+
 fn do_bool_or(vm: &VirtualMachine, lhs: &PyObjectRef, rhs: &PyObjectRef) -> PyResult {
     if objtype::isinstance(lhs, &vm.ctx.bool_type())
         && objtype::isinstance(rhs, &vm.ctx.bool_type())