Improved diagnostic for the situation where overload matching fails to find any applicable overloads. This addresses #6069.

Author: msfterictraut

packages/pyright-internal/src/analyzer/typeEvaluator.ts

@@ -8887,7 +8887,7 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
 
         // Create a helper function that evaluates the overload that best
         // matches the arg/param lists.
-        function evaluateUsingBestMatchingOverload(skipUnknownArgCheck: boolean) {
+        function evaluateUsingBestMatchingOverload(skipUnknownArgCheck: boolean, emitNoOverloadFoundError: boolean) {
             // Find the match with the smallest argument match score. If there
             // are more than one with the same score, use the one with the
             // largest index. Later overloads tend to be more general.
@@ -8898,6 +8898,27 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
                 return current.argumentMatchScore < previous.argumentMatchScore ? current : previous;
             });
 
+            // If there is more than one filtered match, report that no match
+            // was possible and emit a diagnostic that provides the most likely.
+            if (emitNoOverloadFoundError) {
+                const functionName = bestMatch.overload.details.name || '<anonymous function>';
+                const diagnostic = addDiagnostic(
+                    AnalyzerNodeInfo.getFileInfo(errorNode).diagnosticRuleSet.reportGeneralTypeIssues,
+                    DiagnosticRule.reportGeneralTypeIssues,
+                    Localizer.Diagnostic.noOverload().format({ name: functionName }),
+                    errorNode
+                );
+
+                const overrideDecl = bestMatch.overload.details.declaration;
+                if (diagnostic && overrideDecl) {
+                    diagnostic.addRelatedInfo(
+                        Localizer.DiagnosticAddendum.overloadIndex().format({ index: bestMatch.overloadIndex + 1 }),
+                        overrideDecl.path,
+                        overrideDecl.range
+                    );
+                }
+            }
+
             const effectiveTypeVarContext = typeVarContext ?? new TypeVarContext();
             effectiveTypeVarContext.addSolveForScope(getTypeVarScopeIds(bestMatch.overload));
             effectiveTypeVarContext.unlock();
@@ -8915,7 +8936,10 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
         // use the normal type matching mechanism because it is faster and
         // will provide a clearer error message.
         if (filteredMatchResults.length === 1) {
-            return evaluateUsingBestMatchingOverload(/* skipUnknownArgCheck */ false);
+            return evaluateUsingBestMatchingOverload(
+                /* skipUnknownArgCheck */ false,
+                /* emitNoOverloadFoundError */ false
+            );
         }
 
         let expandedArgTypes: (Type | undefined)[][] | undefined = [argList.map((arg) => undefined)];
@@ -8974,7 +8998,10 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
         // in speculative mode because it's very expensive, and we're going to
         // suppress the diagnostic anyway.
         if (!isDiagnosticSuppressedForNode(errorNode) && !isTypeIncomplete) {
-            const result = evaluateUsingBestMatchingOverload(/* skipUnknownArgCheck */ true);
+            const result = evaluateUsingBestMatchingOverload(
+                /* skipUnknownArgCheck */ true,
+                /* emitNoOverloadFoundError */ true
+            );
 
             // Replace the result with an unknown type since we don't know
             // what overload should have been used.

packages/pyright-internal/src/localization/localize.ts

@@ -1249,6 +1249,8 @@ export namespace Localizer {
             new ParameterizedString<{ type: string }>(getRawString('DiagnosticAddendum.noOverloadAssignable'));
         export const orPatternMissingName = () =>
             new ParameterizedString<{ name: string }>(getRawString('DiagnosticAddendum.orPatternMissingName'));
+        export const overloadIndex = () =>
+            new ParameterizedString<{ index: number }>(getRawString('DiagnosticAddendum.overloadIndex'));
         export const overloadSignature = () => getRawString('DiagnosticAddendum.overloadSignature');
         export const overloadNotAssignable = () =>
             new ParameterizedString<{ name: string }>(getRawString('DiagnosticAddendum.overloadNotAssignable'));

packages/pyright-internal/src/localization/package.nls.en-us.json

@@ -633,6 +633,7 @@
         "newMethodSignature": "Signature of __new__ is \"{type}\"",
         "noOverloadAssignable": "No overloaded function matches type \"{type}\"",
         "orPatternMissingName": "Missing names: {name}",
+        "overloadIndex": "Overload {index} is the closest match",
         "overloadSignature": "Overload signature is defined here",
         "overloadNotAssignable": "One or more overloads of \"{name}\" is not assignable",
         "overriddenMethod": "Overridden method",

packages/pyright-internal/src/tests/typeEvaluator1.test.ts

@@ -1275,7 +1275,7 @@ test('Tuple6', () => {
 test('Tuple7', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['tuple7.py']);
 
-    TestUtils.validateResults(analysisResults, 1);
+    TestUtils.validateResults(analysisResults, 2);
 });
 
 test('Tuple8', () => {

packages/pyright-internal/src/tests/typeEvaluator2.test.ts

@@ -75,7 +75,7 @@ test('Assignment1', () => {
 test('Assignment2', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['assignment2.py']);
 
-    TestUtils.validateResults(analysisResults, 2);
+    TestUtils.validateResults(analysisResults, 3);
 });
 
 test('Assignment3', () => {
@@ -1389,7 +1389,7 @@ test('TypedDict11', () => {
 test('TypedDict12', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['typedDict12.py']);
 
-    TestUtils.validateResults(analysisResults, 6);
+    TestUtils.validateResults(analysisResults, 7);
 });
 
 test('TypedDict13', () => {

packages/pyright-internal/src/tests/typeEvaluator3.test.ts

@@ -977,7 +977,7 @@ test('TypePromotions1', () => {
 test('Index1', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['index1.py']);
 
-    TestUtils.validateResults(analysisResults, 7);
+    TestUtils.validateResults(analysisResults, 10);
 });
 
 test('ProtocolModule2', () => {
@@ -1633,7 +1633,7 @@ test('Subscript1', () => {
 
 test('Subscript2', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['subscript2.py']);
-    TestUtils.validateResults(analysisResults, 5);
+    TestUtils.validateResults(analysisResults, 8);
 });
 
 test('Subscript3', () => {
@@ -1642,7 +1642,7 @@ test('Subscript3', () => {
     // Analyze with Python 3.9 settings.
     configOptions.defaultPythonVersion = PythonVersion.V3_9;
     const analysisResults39 = TestUtils.typeAnalyzeSampleFiles(['subscript3.py'], configOptions);
-    TestUtils.validateResults(analysisResults39, 32);
+    TestUtils.validateResults(analysisResults39, 37);
 
     // Analyze with Python 3.10 settings.
     // These are disabled because PEP 637 was rejected.

packages/pyright-internal/src/tests/typeEvaluator4.test.ts

@@ -311,7 +311,7 @@ test('Overload7', () => {
 
 test('Overload8', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['overload8.py']);
-    TestUtils.validateResults(analysisResults, 2);
+    TestUtils.validateResults(analysisResults, 4);
 });
 
 test('Overload10', () => {
@@ -326,7 +326,7 @@ test('Overload11', () => {
 
 test('Overload12', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['overload12.py']);
-    TestUtils.validateResults(analysisResults, 1);
+    TestUtils.validateResults(analysisResults, 2);
 });
 
 test('Overload13', () => {
@@ -527,7 +527,7 @@ test('MemberAccess18', () => {
 
 test('MemberAccess19', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['memberAccess19.py']);
-    TestUtils.validateResults(analysisResults, 5);
+    TestUtils.validateResults(analysisResults, 10);
 });
 
 test('MemberAccess20', () => {