Fix for #18

Author: tenntenn

forcetypeassert.go

@@ -90,6 +90,11 @@ func checkAssignStmt(pass *analysis.Pass, result *Panicable, n *ast.AssignStmt)
 	}
 
 	switch {
+
+	// if right hand is a call expression, assign statement can't assert boolean value which describes type assertion is succeeded
+	case len(n.Rhs) == 1 && isCallExpr(n.Rhs[0]):
+		pass.Reportf(n.Pos(), "right hand must be only type assertion")
+		return false
 	// if right hand has 2 or more values, assign statement can't assert boolean value which describes type assertion is succeeded
 	case len(n.Rhs) > 1:
 		pass.Reportf(n.Pos(), "right hand must be only type assertion")
@@ -113,6 +118,10 @@ func checkValueSpec(pass *analysis.Pass, result *Panicable, n *ast.ValueSpec) bo
 	}
 
 	switch {
+	// if right hand is a call expression, assign statement can't assert boolean value which describes type assertion is succeeded
+	case len(n.Values) == 1 && isCallExpr(n.Values[0]):
+		pass.Reportf(n.Pos(), "right hand must be only type assertion")
+		return false
 	// if right hand has 2 or more values, assign statement can't assert boolean value which describes type assertion is succeeded
 	case len(n.Values) > 1:
 		pass.Reportf(n.Pos(), "right hand must be only type assertion")
@@ -148,3 +157,8 @@ func findTypeAssertion(exprs []ast.Expr) *ast.TypeAssertExpr {
 	}
 	return nil
 }
+
+func isCallExpr(expr ast.Expr) bool {
+	_, isCallExpr := expr.(*ast.CallExpr)
+	return isCallExpr
+}

forcetypeassert_test.go

@@ -10,7 +10,7 @@ import (
 
 func Test(t *testing.T) {
 	testdata := analysistest.TestData()
-	analysistest.Run(t, testdata, forcetypeassert.Analyzer, "a")
+	analysistest.Run(t, testdata, forcetypeassert.Analyzer, "a", "issue")
 }
 
 func TestResult(t *testing.T) {

testdata/src/issue/issue18.go

@@ -0,0 +1,12 @@
+// https://github.com/gostaticanalysis/forcetypeassert/issues/18
+package issue
+
+type M struct{}
+
+func (M) F() (bool, bool) { return true, true }
+
+var _, ok = any(nil).(M).F() // want `right hand must be only type assertion`
+func Test(x any) bool {
+	_, ok := x.(M).F() // want `right hand must be only type assertion`
+	return ok
+}