Function checkUnusedTypeParameters

test/fixtures/snapshot/typescript.js:82046–82080

(node, addDiagnostic)

            }
        }
        function checkUnusedTypeParameters(node, addDiagnostic) {
            // Only report errors on the last declaration for the type parameter container;
            // this ensures that all uses have been accounted for.
            var declarations = getSymbolOfNode(node).declarations;
            if (!declarations || ts.last(declarations) !== node)
                return;
            var typeParameters = ts.getEffectiveTypeParameterDeclarations(node);
            var seenParentsWithEveryUnused = new ts.Set();
            for (var _i = 0, typeParameters_3 = typeParameters; _i < typeParameters_3.length; _i++) {
                var typeParameter = typeParameters_3[_i];
                if (!isTypeParameterUnused(typeParameter))
                    continue;
                var name = ts.idText(typeParameter.name);
                var parent = typeParameter.parent;
                if (parent.kind !== 190 /* SyntaxKind.InferType */ && parent.typeParameters.every(isTypeParameterUnused)) {
                    if (ts.tryAddToSet(seenParentsWithEveryUnused, parent)) {
                        var sourceFile = ts.getSourceFileOfNode(parent);
                        var range = ts.isJSDocTemplateTag(parent)
                            // Whole @template tag
                            ? ts.rangeOfNode(parent)
                            // Include the `<>` in the error message
                            : ts.rangeOfTypeParameters(sourceFile, parent.typeParameters);
                        var only = parent.typeParameters.length === 1;
                        //TODO: following line is possible reason for bug #41974, unusedTypeParameters_TemplateTag
                        var message = only ? ts.Diagnostics._0_is_declared_but_its_value_is_never_read : ts.Diagnostics.All_type_parameters_are_unused;
                        var arg0 = only ? name : undefined;
                        addDiagnostic(typeParameter, 1 /* UnusedKind.Parameter */, ts.createFileDiagnostic(sourceFile, range.pos, range.end - range.pos, message, arg0));
                    }
                }
                else {
                    //TODO: following line is possible reason for bug #41974, unusedTypeParameters_TemplateTag
                    addDiagnostic(typeParameter, 1 /* UnusedKind.Parameter */, ts.createDiagnosticForNode(typeParameter, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, name));
                }
            }
        }
        function isTypeParameterUnused(typeParameter) {
            return !(getMergedSymbol(typeParameter.symbol).isReferenced & 262144 /* SymbolFlags.TypeParameter */) && !isIdentifierThatStartsWithUnderscore(typeParameter.name);
        }