How to I get the declared type from a TypeReferenceType in TypeScript Compiler API?

[ctaggart]

How to I get the declared type from a TypeReferenceType in TypeScript Compiler API? I tried checker.getContextualType and a bunch of other calls over several hours. I'm using the latest typescript@next which is typescript@^2.7.0-dev.20171117. The test file is from yarn add @types/mocha --dev.

    import * as ts from "typescript";
    import * as fs from "fs";

    const tsPath = "node_modules/@types/mocha/index.d.ts"
    const options: ts.CompilerOptions = { target: ts.ScriptTarget.ES2015 }
    const host = ts.createCompilerHost(options, true);
    const program = ts.createProgram([tsPath], options, host)
    const checker = program.getTypeChecker()
    const sourceFile = program.getSourceFile(tsPath)
    // console.log(sourceFile)

    function visitNode(node: ts.Node){
        switch (node.kind) {
            case ts.SyntaxKind.ClassDeclaration:
                const cd = (<ts.ClassDeclaration>node);
                // console.log(cd.name.getText())
                if(cd.name.getText() === "Doc"){
                    printBaseClass(cd)
                }
        }
        ts.forEachChild(node, visitNode)
    }

    ts.forEachChild(sourceFile, visitNode);

    function printBaseClass(cd: ts.ClassDeclaration){
        // console.log(cd)
        for(const hc of cd.heritageClauses) {
            console.log("heritage clause: " + hc.getText())
            for(const hctp of hc.types){
                // hctp is a ts.ExpressionWithTypeArguments

                const ct = checker.getContextualType(hctp.expression)
                console.log("contextual type: " + ct) // undefined
            }

        }
    }

Also submitted to stackoverflow.

[ajafff]

import {isTypeReference} from "tsutils";
declare let type: ts.Type;
if (isTypeReference(type)) {
    type = type.target; // is this what you want?
}

[ctaggart]

@ajafff The tsutils library looks nice. Unfortunately no. I'm looking for the ClassDeclaration of the base class, in this case `Mocha.Reporters.Base.

import * as ts from "typescript";
import * as fs from "fs";
import {isTypeReference, isClassDeclaration} from "tsutils";

const tsPath = "node_modules/@types/mocha/index.d.ts"
const options: ts.CompilerOptions = { target: ts.ScriptTarget.ES2015 }
const host = ts.createCompilerHost(options, true);
const program = ts.createProgram([tsPath], options, host)
const checker = program.getTypeChecker()
const sourceFile = program.getSourceFile(tsPath)
// console.log(sourceFile)

function visitNode(node: ts.Node){
    switch (node.kind) {
        case ts.SyntaxKind.ClassDeclaration:
            const cd = (<ts.ClassDeclaration>node);
            // console.log(cd.name.getText())
            if(cd.name.getText() === "Doc"){
                printBaseClass(cd)
            }
    }
    ts.forEachChild(node, visitNode)
}

ts.forEachChild(sourceFile, visitNode);

function getFullTypeName (tp: ts.Type){
    if(tp.symbol){
        return checker.getFullyQualifiedName(tp.symbol)
    } else {
        return ""
    }
}

function getFullNodeName (nd: ts.Node){
    const tp =checker.getTypeAtLocation(nd)
    return getFullTypeName(tp)
}

function printBaseClass(cd: ts.ClassDeclaration){
    // console.log(cd)
    for(const hc of cd.heritageClauses) {
        console.log("heritage clause: " + hc.getText())

        console.log("hc name " + getFullNodeName(hc))

        for(const hctp of hc.types){
            let tp = checker.getTypeFromTypeNode(hctp)
            console.log(getFullTypeName(tp))

            if (isTypeReference(tp)) {
                const targetNode = checker.typeToTypeNode(tp.target)
                if(isClassDeclaration(targetNode)){
                    console.log("found it")
                } else {
                    console.log("targetNode is not a class " + targetNode.kind) // 159 TypeReference
                }
            }
        }
    }
}

Just pushed this to base-class branch here:
https://github.com/ctaggart/TsAst/blob/base-class/base-class.ts

[ajafff]

const targetNode = checker.typeToTypeNode(tp.target)

This always creates a new type node. Note that a TypeNode will never be a ClassDeclaration. A TypeNode is something you use in type position, for example the Foo in let foo: Foo.

You probably want getFullTypeName(tp.target) or look for the class declaration in tp.target.declaration or tp.target.symbol.declarations

[ctaggart]

Thank you @ajafff! It is working now.

import * as ts from "typescript";
import * as fs from "fs";
import {isTypeReference, isClassDeclaration} from "tsutils";

const tsPath = "node_modules/@types/mocha/index.d.ts"
const options: ts.CompilerOptions = { target: ts.ScriptTarget.ES2015 }
const host = ts.createCompilerHost(options, true);
const program = ts.createProgram([tsPath], options, host)
const checker = program.getTypeChecker()
const sourceFile = program.getSourceFile(tsPath)
// console.log(sourceFile)

function visitNode(node: ts.Node){
    switch (node.kind) {
        case ts.SyntaxKind.ClassDeclaration:
            const cd = (<ts.ClassDeclaration>node);
            // console.log(cd.name.getText())
            if(cd.name.getText() === "Doc"){
                printBaseClass(cd)
            }
    }
    ts.forEachChild(node, visitNode)
}

ts.forEachChild(sourceFile, visitNode);

function getFullTypeName (tp: ts.Type){
    if(tp.symbol){
        return checker.getFullyQualifiedName(tp.symbol)
    } else {
        return ""
    }
}

function getFullNodeName (nd: ts.Node){
    const tp =checker.getTypeAtLocation(nd)
    return getFullTypeName(tp)
}

function printBaseClass(cd: ts.ClassDeclaration){
    // console.log(cd)
    for(const hc of cd.heritageClauses) {
        console.log("heritage clause: " + hc.getText())
        console.log("hc name " + getFullNodeName(hc))
        for(const hctp of hc.types){
            let tp = checker.getTypeFromTypeNode(hctp)
            console.log(getFullTypeName(tp))

            if (isTypeReference(tp)) {
                let dcs = tp.target.symbol.declarations
                console.log(dcs.length + " declarations")
                for(const dc of dcs){
                    console.log(getFullNodeName(dc))
                    if(isClassDeclaration(dc)){
                        for(const mb of dc.members){
                            console.log("  member " + mb.getText())
                        }
                    }
                }
            }
        }
    }
}