问题
I'm using the built-in parser to generate the AST from source code:
const ts = require('typescript')
//...
const ast = ts.createSourceFile(filename, fs.readFileSync(filename).toString(), ts.ScriptTarget.ES6, true)
Is there a way to get the inferred type of a variable from the AST? For example, in the code below, bar
is of type IBar
. The compiler knows about that type---bar.foo()
doesn't compile---how can I programmatically get the type?
interface IBar { bar() }
const foo : IBar = //...
export const bar = foo
回答1:
The compiler knows about that type---bar.foo() doesn't compile---how can I programmatically get the type?
The AST
is not the complete story for TypeChecking. You need a TypeChecker
.
The simplest solution is to create a program (some docs https://basarat.gitbooks.io/typescript/content/docs/compiler/program.html) and then use program.getTypeChecker
(more docs https://basarat.gitbooks.io/typescript/content/docs/compiler/checker.html) 🌹
回答2:
As far as I can tell this does the trick:
// load typechecker for file
const program = ts.createProgram([filename], {});
const typeChecker = program.getTypeChecker()
// now get ast
const ast = ts.createSourceFile(filename, filecontents, ts.ScriptTarget.ES6, true))
// get node under question using ts.forEachChild (not shown here)
const node = // ...
const type = typeChecker.getTypeAtLocation(node);
The only weird part is that in a variable declaration, the "node" must be the value
(aka FirstLiteralToken) and not the label
(aka Identifier)---otherwise, the type is undefined.
For example, if the file contents are const foo = 123
, passing the node for "foo" to typeChecker#getTypeAtLocation won't work. You must pass the node for "123"
来源:https://stackoverflow.com/questions/34736109/how-do-you-get-inferred-type-from-a-typescript-ast