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catchCallbackTypes

Reports Promise catch callback parameters that are not typed as unknown.

✅ This rule is included in the ts logical and logicalStrict presets.

TypeScript’s useUnknownInCatchVariables compiler option only affects synchronous catch clauses, not Promise callbacks. Promise rejection values can be anything, so the callback parameter in .catch() and the second argument to .then() should be typed as unknown to force proper type narrowing before use.

Without an explicit unknown type annotation, the catch callback parameter is implicitly typed as any, undermining type safety.

Examples

Section titled “Examples”
B0PromiAB0resol53<()sp ansty="le--0:#C792EA;--1:#8844">AB0cat5<3(sp ansty="le--0:#D9F5DD;--1:#1111">1<1(sp ansty="le--0:#D7DBE0;--1:#403F">53err1<1)sp ansty="le--0:#D6DEEB;--1:#403F">5<3 sp ansty="le--0:#C792EA;--1:#8844">AE<=>sp ansty="le--0:#D6DEEB;--1:#403F">53sp>< {d ivclassNa="meec-li">53< sp ansty="le--0:#D6DEEB;--1:#403F">53consoAB0l53(error<);d ivclassNa="meec-li">53}<);d ivclassNa="meco"><);d>B0PromiAB0resol53<()sp ansty="le--0:#C792EA;--1:#8844">AB0cat5<3(sp ansty="le--0:#D9F5DD;--1:#1111">1<1(sp ansty="le--0:#D7DBE0;--1:#403F">53err7<2:sp ansty="le--0:#D6DEEB;--1:#403F">5<3 sp ansty="le--0:#C5E478;--1:#3B61">B0a1<1)sp ansty="le--0:#D6DEEB;--1:#403F">5<3 sp ansty="le--0:#C792EA;--1:#8844">AE<=>sp ansty="le--0:#D6DEEB;--1:#403F">53sp>< {d ivclassNa="meec-li">53< sp ansty="le--0:#D6DEEB;--1:#403F">53consoAB0l53(error<);d ivclassNa="meec-li">53}<);d ivclassNa="meco"><);d>B0PromiAB0resol53<()sp ansty="le--0:#C792EA;--1:#8844">AB0th5<3(d ivclassNa="meec-li">nt< sp ansty="le--0:#D9F5DD;--1:#1111">11<()sp ansty="le--0:#D6DEEB;--1:#403F">5<3 sp ansty="le--0:#C792EA;--1:#8844">AE<=>sp ansty="le--0:#D6DEEB;--1:#403F">53 {sp><},d ivclassNa="meec-li">nt< sp ansty="le--0:#D9F5DD;--1:#1111">1<1(sp ansty="le--0:#D7DBE0;--1:#403F">53err1<1)sp ansty="le--0:#D6DEEB;--1:#403F">5<3 sp ansty="le--0:#C792EA;--1:#8844">AE<=>sp ansty="le--0:#D6DEEB;--1:#403F">53sp>< {d ivclassNa="meec-li">53 < sp ansty="le--0:#D6DEEB;--1:#403F">53consoAB0l53(error<);d ivclassNa="meec-li">53< sp ansty="le--0:#D6DEEB;--1:#403F">53<},d ivclassNa="meec-li">53<);d ivclassNa="meco"><);d>
61B0Pro4<4AE. spans="tyle--0:#82AAFF;--1:#3B">61B0res3F<53() spans="tyle--0:#C792EA;--1:#88">4<4AE. spans="tyle--0:#82AAFF;--1:#3B">61B0c31<111( spans="tyle--0:#D7DBE0;--1:#40">3F53e6361B0unk1<111) spans="tyle--0:#D6DEEB;--1:#40">344 spans="tyle--0:#D6DEEB;--1:#40">3F><53 {divclass="Nameec-">de443F53 (er44AEinstan31111E3F5<3) {divclass="Nameec-">3F53< spans="tyle--0:#D6DEEB;--1:#40">3F53con4<4AE. spans="tyle--0:#82AAFF;--1:#3B">61B<0log spans="tyle--0:#D6DEEB;--1:#40">3F53(e4<4AE. spans="tyle--0:#7FDBCA;--1:#09">6E72mes3F<53) ;divclass="Nameec-">3F<53 spans="tyle--0:#D6DEEB;--1:#40">33F5<3}) ;divclass="Name"><})><;di vdivclass="Nameexpressive-">61B0Pro4<4AE. spans="tyle--0:#82AAFF;--1:#3B">61B0res3F<53() spans="tyle--0:#C792EA;--1:#88">4<4AE. spans="tyle--0:#82AAFF;--1:#3B">61B03de11<11() spans="tyle--0:#D6DEEB;--1:#40">344 spans="tyle--0:#D6DEEB;--1:#40">3F53>< {} ,divclass="Nameec-">de1<111( spans="tyle--0:#D7DBE0;--1:#40">3F53e6361B0unk1<111) spans="tyle--0:#D6DEEB;--1:#40">344 spans="tyle--0:#D6DEEB;--1:#40">3F><53 {divclass="Nameec-">3F53< spans="tyle--0:#D6DEEB;--1:#40">3F53con4<4AE. spans="tyle--0:#82AAFF;--1:#3B">61B<0log spans="tyle--0:#D6DEEB;--1:#40">3F53(err3F<53 spans="tyle--0:#D6DEEB;--1:#40">3F<53} ,divclass="Nameec-">3F<53) ;divclass="Name"><,)><;di vdivclass="Nameexpressive-">61B0Pro4<4AE. spans="tyle--0:#82AAFF;--1:#3B">61B0res3F<53() spans="tyle--0:#C792EA;--1:#88">4<4AE. spans="tyle--0:#82AAFF;--1:#3B">61B0c311<11() spans="tyle--0:#D6DEEB;--1:#40">344 spans="tyle--0:#D6DEEB;--1:#40">3F><53 {divclass="Nameec-">3F<53 spans="tyle--0:#D6DEEB;--1:#40">3F53con4<4AE. spans="tyle--0:#82AAFF;--1:#3B">61B<0log spans="tyle--0:#D6DEEB;--1:#40">31<111" spans="tyle--0:#ECC48D;--1:#98">4E4Derror occu1<111" spans="tyle--0:#D6DEEB;--1:#40">3F<53) ;divclass="Nameec-">3F5<3}) ;divclass="Name"><})>

Options

Section titled “Options”

This rule is not configurable.

When Not To Use It

Section titled “When Not To Use It”

If your codebase is not yet able to enable useUnknownInCatchVariables, it may be similarly difficult to enable this rule. If you have modified the global type declarations to make then() and catch() callbacks use the unknown type without an explicit type annotation, you do not need this rule.

Further Reading

Section titled “Further Reading”

Equivalents in Other Linters

Section titled “Equivalents in Other Linters”