TS1059
TypeScriptERRORNotableSyntaxHIGH confidence
A promise must have a 'then' method.
Production Risk
Build will fail; resolve before shipping.
What this means
A syntax error (TS1059): A promise must have a 'then' method.. This diagnostic is emitted by the TypeScript compiler when a promise must have a 'then' method..
Why it happens
- 1Incorrect TypeScript syntax or type usage
- 2Type mismatch between declared and actual value
How to reproduce
TypeScript compiler reports TS1059 during type checking.
trigger — this will error
trigger — this will error
// Triggers TS1059 // A promise must have a 'then' method.
expected output
error TS1059: A promise must have a 'then' method.
Fix
Address the TypeScript diagnostic
WHEN When this error is reported by the compiler
Address the TypeScript diagnostic
// Run the TypeScript compiler for details: npx tsc --noEmit // Use the TypeScript playground to test your code: // https://www.typescriptlang.org/play
Why this works
Review the full error message and location; the TypeScript handbook provides guidance on each error category.
Sources
Official documentation ↗
TypeScript Compiler Diagnostics
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