PY-80627 At least two @overload-decorated definitions must be present

GitOrigin-RevId: c40090f12631d61cfbb151f52cf709a8a2cd2383

python/python-psi-impl/resources/messages/PyPsiBundle.properties

@@ -1047,6 +1047,8 @@ INSP.overloads.series.overload.decorated.methods.should.always.be.followed.by.im
 INSP.overloads.series.overload.decorated.functions.should.always.be.followed.by.implementation=A series of @overload-decorated functions should always be followed by an implementation that is not @overload-ed
 INSP.overloads.this.method.overload.signature.not.compatible.with.implementation=Signature of this @overload-decorated method is not compatible with the implementation
 INSP.overloads.this.function.overload.signature.not.compatible.with.implementation=Signature of this @overload-decorated function is not compatible with the implementation
+INSP.overloads.at.least.two.overload.decorated.methods.must.be.present=At least two @overload-decorated methods must be present
+INSP.overloads.at.least.two.overload.decorated.functions.must.be.present=At least two @overload-decorated functions must be present
 
 # PyOverridesInspection
 INSP.NAME.invalid.usages.of.override.decorator=Invalid usages of @override decorator

python/python-psi-impl/src/com/jetbrains/python/inspections/PyOverloadsInspection.kt

@@ -55,6 +55,15 @@ class PyOverloadsInspection : PyInspection() {
 
       if (overloads.isEmpty()) return
 
+      if (overloads.size == 1) {
+        registerProblem(overloads[0].nameIdentifier, if (owner is PyClass) {
+          PyPsiBundle.message("INSP.overloads.at.least.two.overload.decorated.methods.must.be.present")
+        }
+        else {
+          PyPsiBundle.message("INSP.overloads.at.least.two.overload.decorated.functions.must.be.present")
+        })
+      }
+
       var requiresImplementation = true
       if (owner is PyClass) {
         if (isProtocol(owner, myTypeEvalContext)) {

python/testData/inspections/PyOverloadsInspection/singleOverload.py

@@ -0,0 +1,40 @@
+from typing import overload
+
+
+@overload
+def <warning descr="At least two @overload-decorated functions must be present">foo</warning>() -> None: ...
+
+
+def foo() -> None:
+    pass
+
+
+class A:
+    @overload
+    def <warning descr="At least two @overload-decorated methods must be present">foo</warning>() -> None: ...
+
+    def foo() -> None:
+        pass
+
+
+@overload
+def bar(x: int) -> None: ...
+
+
+@overload
+def bar(x: str) -> None: ...
+
+
+def bar(x: int | str) -> None:
+    pass
+
+
+class B:
+    @overload
+    def bar(x: int) -> None: ...
+
+    @overload
+    def bar(x: str) -> None: ...
+
+    def bar(x: int | str) -> None:
+        pass

python/testSrc/com/jetbrains/python/inspections/PyOverloadsInspectionTest.java

@@ -16,7 +16,6 @@
 package com.jetbrains.python.inspections;
 
 import com.jetbrains.python.fixtures.PyInspectionTestCase;
-import com.jetbrains.python.psi.LanguageLevel;
 import org.jetbrains.annotations.NotNull;
 
 public class PyOverloadsInspectionTest extends PyInspectionTestCase {
@@ -41,14 +40,13 @@ public class PyOverloadsInspectionTest extends PyInspectionTestCase {
     doTest();
   }
 
+  public void testSingleOverload() {
+    doTest();
+  }
+
   @NotNull
   @Override
   protected Class<? extends PyInspection> getInspectionClass() {
     return PyOverloadsInspection.class;
   }
-
-  @Override
-  protected void doTest() {
-    runWithLanguageLevel(LanguageLevel.PYTHON35, () -> super.doTest());
-  }
 }