go/types: CheckExpr doesn't return partial results

[muirdm]

What version of Go are you using (go version)?

$ go version
go version go1.13 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

Darwin/amd64

What did you do?

I used types.CheckExpr to check the expression "foo{i}" in the package:

package fake
type foo struct {}
var _  = foo{i}

What did you expect to see?

I expected to have some way to type check resiliently and get the type for my *ast.CompositeLit.

See https://play.golang.org/p/dDqvcc-jSFM

What did you see instead?

The error for the un-type checkable "i" identifier is returned and no type checking is done. When using *types.Checker you can set the "Error" callback in the config so the type checker doesn't bail out, but CheckExpr doesn't set "Error" in the config.

I was experimenting with types.CheckExpr in gopls to provide completions in the face of certain kinds of syntax errors, but its utility is limited because it isn't resilient to errors.

[toothrot]

/cc @griesemer