Go compilation error

What this failure means

The Go compiler rejected the package because of a semantic error — undefined identifier, type mismatch, unused import, or interface non-compliance. The binary cannot be produced until the errors are resolved.

Symptoms

Faultline looks for one or more of these log fragments:

imported and not used
declared and not used
does not implement
undefined:
cannot use
too many arguments in call to
not enough arguments in call to
cannot assign to

Diagnosis

The Go compiler emitted one or more hard errors and aborted the build. These are always deterministic: the source must be corrected before go build ./... can succeed.

Common error classes:

• undefined: — a symbol, function, or type is referenced but not declared in the current package or any imported package.
• cannot use X as Y — a value of one type is passed where a different type is required, and no implicit conversion exists.
• imported and not used — a package was imported but none of its exported names appear in the file.
• declared and not used — a local variable was declared but never read.
• does not implement — a concrete type is used where an interface is expected but is missing one or more methods.

Fix steps

1. Run go build ./... locally to see the full diagnostic output:

   go build ./... 2>&1 | head -30
   

2. For undefined: Foo: import the package that defines Foo or move the declaration into scope.

3. For cannot use x (variable of type A) as type B: correct the type or add an explicit conversion where the semantics are safe.

4. For imported and not used: remove the unused import, or add a blank import _ "pkg" if the side-effect is intentional.

5. For declared and not used: use the variable or replace it with _.

6. For does not implement: add the missing method to the concrete type, or use the correct type that already satisfies the interface.

Validation

• Run go build ./... locally and confirm zero errors.
• Run go vet ./... to catch additional semantic issues before CI.
• Confirm the CI build step exits zero.

Why it matters

Go compilation errors are deterministic and hard — the build stops immediately with no output binary. All downstream test and deploy steps are blocked until the root error is fixed. The compiler message always names the exact file, line, and column: start there and work outward.

Prevention

• Run go build ./... and go vet ./... as a pre-push hook.
• Enable editor integration (gopls / VS Code Go) so errors surface on save.
• Add a dedicated go build step before the test step in CI so compile errors produce a clear signal rather than hiding inside a test failure.

Try it locally

go build ./...
go vet ./...
go build ./...

How Faultline detects it

Use faultline explain go-compile-error to see the full playbook.

faultline analyze build.log
faultline explain go-compile-error

Generated from playbooks/bundled/log/build/go-compile-error.yaml. Do not edit directly.