Bytecode DSL: fix f-strings with non-TruffleString components

Author: steve-s

graalpython/com.oracle.graal.python.test/src/tests/test_string.py

@@ -1210,3 +1210,22 @@ def test_raw_unicode_escape_does_not_alter_encoded_string():
     original = "[\\xA0]"
     decoded = bytes(original, encoding="raw-unicode-escape").decode("raw-unicode-escape")
     assert original == decoded
+
+
+def test_fstring():
+    class FunkyFormat:
+        def __init__(self, f):
+            self.f = f
+        def __format__(self, _):
+            return self.f
+
+    class FunkyStr(str):
+        def __str__(self):
+            return self
+
+    assert type(f"{FunkyStr('abc')}") == FunkyStr
+    assert type(f"hello {FunkyFormat('world')}!") == str
+
+    assert f"hello {FunkyFormat('world')}!" == "hello world!"
+    assert f"hello {FunkyStr('world')}!" == "hello world!"
+    assertRaises(TypeError, lambda: f"hello {FunkyFormat(33)}!")

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/bytecode_dsl/PBytecodeDSLRootNode.java

@@ -218,6 +218,8 @@
 import com.oracle.graal.python.nodes.object.GetClassNode;
 import com.oracle.graal.python.nodes.object.GetClassNode.GetPythonObjectClassNode;
 import com.oracle.graal.python.nodes.object.IsNode;
+import com.oracle.graal.python.nodes.util.CannotCastException;
+import com.oracle.graal.python.nodes.util.CastToTruffleStringNode;
 import com.oracle.graal.python.nodes.util.ExceptionStateNodes;
 import com.oracle.graal.python.runtime.ExecutionContext.CalleeContext;
 import com.oracle.graal.python.runtime.IndirectCallData.BoundaryCallData;
@@ -3203,12 +3205,22 @@ public static final class BuildString {
         public static Object perform(
                         int length,
                         @Variadic Object[] strings,
+                        @Bind Node inliningTarget,
+                        @Cached CastToTruffleStringNode castToStringNode,
                         @Cached TruffleStringBuilder.AppendStringNode appendNode,
-                        @Cached TruffleStringBuilder.ToStringNode toString) {
+                        @Cached TruffleStringBuilder.ToStringNode toString,
+                        @Cached PRaiseNode raise) {
             var tsb = TruffleStringBuilderUTF32.create(PythonUtils.TS_ENCODING);
             CompilerAsserts.partialEvaluationConstant(length);
             for (int i = 0; i < length; i++) {
-                appendNode.execute(tsb, (TruffleString) strings[i]);
+                try {
+                    appendNode.execute(tsb, castToStringNode.execute(inliningTarget, strings[i]));
+                } catch (CannotCastException ex) {
+                    // Python should only permit str literals or calls to `format` builtin as
+                    // argument to this operation. The `format` builtin already ensures the result
+                    // is a Python string.
+                    throw CompilerDirectives.shouldNotReachHere(ex);
+                }
             }
             return toString.execute(tsb);
         }