swc/crates/swc_ecma_parser/tests/tsc/stringMappingOverPatternLiterals.ts

// non-template
type A = "aA";
type B = Uppercase<A>;
type C = Lowercase<A>;

// templated
type ATemplate = `aA${string}`;
type BTemplate = Uppercase<ATemplate>;
type CTemplate = Lowercase<ATemplate>;

function f1(
    a: A,
    b: B,
    c: C,
    a_template: ATemplate,
    b_template: BTemplate,
    c_template: CTemplate
) {
    // non-template versions should be assignable to templated versions (empty string matches string)
    a_template = a;
    b_template = b;
    c_template = c;

    // not the other way around
    a = a_template;
    b = b_template;
    c = c_template;

    // Additionally, all the template versions should be mutually incompatible (they describe differing sets)
    a_template = b_template;
    a_template = c_template;

    b_template = a_template;
    b_template = c_template;

    c_template = a_template;
    c_template = b_template;
}

// Raw string mapping assignability

function f2(x1: string, x2: Uppercase<string>, x3: Lowercase<string>) {
    // ok
    x1 = x2;
    x1 = x3;

    x2 = "ABC";
    x3 = "abc";

    // should fail (sets do not match)
    x2 = x1;
    x2 = x3;
    x3 = x1;
    x3 = x2;

    x2 = "AbC";
    x3 = "AbC";
}

// Mappings over mappings

function f3(
    x1: Uppercase<string>,
    x2: Uppercase<Uppercase<string>>,
    x3: Uppercase<Lowercase<string>>) {

    // _ideally_ these would all be equivalent
    x1 = x2;
    x1 = x3;

    x2 = x1;
    x2 = x3;

    // you'd think these were equivalent - the outer `Uppercase` conceptually
    // makes the inner `Lowercase` effectively a noop - but that's not so;
    // the german sharp s makes that not completely true (lowercases to ss,
    // which then uppercases to SS), so arbitrary nestings of mappings make differing sets!
    x3 = x1;
    x3 = x2;

    // and this should also not be equivlent to any others
    var x4: Lowercase<Uppercase<string>> = null as any;
    x1 = x4;
    x2 = x4;
    x3 = x4;

    x4 = x1;
    x4 = x2;
    x4 = x3;
}

// string mapping over non-string pattern literals is preserved

type NonStringPat = Uppercase<`aA${number}${bigint}${boolean}`>;
type EquivalentNonStringPat = `AA${Uppercase<`${number}`>}${Uppercase<`${bigint}`>}${Uppercase<`${boolean}`>}`;

function f4(x1: NonStringPat, x2: EquivalentNonStringPat) {
    // Should both work
    x1 = x2;
    x2 = x1;
}

// Capitalize and uncapitalize on template literals

function f5(
    cap_tem: `A${string}`,
    cap_str: Capitalize<string>,
    cap_tem_map: Capitalize<`A${string}`>,
    cap_tem_map2: Capitalize<`a${string}`>,
    uncap_tem: `a${string}`,
    uncap_str: Uncapitalize<string>,
    uncap_tem_map: Uncapitalize<`A${string}`>,
    uncap_tem_map2: Uncapitalize<`a${string}`>,
) {
    // All these are capitalized
    cap_str = cap_tem;
    cap_str = cap_tem_map;
    cap_str = cap_tem_map2;

    // these are all equivalent
    cap_tem = cap_tem_map;
    cap_tem = cap_tem_map2;
    cap_tem_map = cap_tem_map2;
    cap_tem_map = cap_tem;
    cap_tem_map2 = cap_tem_map;
    cap_tem_map2 = cap_tem;

    // meanwhile, these all require a `A` prefix
    cap_tem = cap_str;
    cap_tem_map = cap_str;
    cap_tem_map2 = cap_str;

    // All these are uncapitalized
    uncap_str = uncap_tem;
    uncap_str = uncap_tem_map;
    uncap_str = uncap_tem_map2;

    // these are all equivalent
    uncap_tem = uncap_tem_map;
    uncap_tem = uncap_tem_map2;
    uncap_tem_map = uncap_tem_map2;
    uncap_tem_map = uncap_tem;
    uncap_tem_map2 = uncap_tem_map;
    uncap_tem_map2 = uncap_tem;

    // meanwhile, these all require a `a` prefix
    uncap_tem = uncap_str;
    uncap_tem_map = uncap_str;
    uncap_tem_map2 = uncap_str;
}