Result-ify src/parser.rs (#608)

* Make ConvertToAst trait fallible

It's got some panics, and we'll be switching those to errors!

* First example of a diagnostic-driven error

Add a diagnostic-driven error `#[wasm_bindgen]` being attached to public
functions, and add some macros to boot to make it easier to generate errors!

* Result-ify `src/parser.rs`

This commit converts all of `src/parser.rs` away from panics to using
`Diagnostic` instead. Along the way this adds a test case per changed `panic!`,
ensuring that we don't regress in these areas!

crates/macro/ui-tests/invalid-attr.rs

@@ -0,0 +1,23 @@
+#![feature(use_extern_macros)]
+
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen(x)]
+pub fn foo() {}
+
+#[wasm_bindgen]
+extern "C" {
+    #[wasm_bindgen(y)]
+    fn bar();
+
+    #[wasm_bindgen z]
+    fn bar();
+
+    #[wasm_bindgen(z2) x]
+    fn bar();
+
+    #[wasm_bindgen {  }]
+    fn bar();
+}

crates/macro/ui-tests/invalid-attr.stderr

@@ -0,0 +1,32 @@
+error: error parsing #[wasm_bindgen] attribute options: failed to parse anything
+ --> $DIR/invalid-attr.rs:7:16
+  |
+7 | #[wasm_bindgen(x)]
+  |                ^
+
+error: error parsing #[wasm_bindgen] attribute options: failed to parse anything
+  --> $DIR/invalid-attr.rs:12:20
+   |
+12 |     #[wasm_bindgen(y)]
+   |                    ^
+
+error: malformed #[wasm_bindgen] attribute
+  --> $DIR/invalid-attr.rs:15:5
+   |
+15 |     #[wasm_bindgen z]
+   |     ^^^^^^^^^^^^^^^^^
+
+error: malformed #[wasm_bindgen] attribute
+  --> $DIR/invalid-attr.rs:18:5
+   |
+18 |     #[wasm_bindgen(z2) x]
+   |     ^^^^^^^^^^^^^^^^^^^^^
+
+error: malformed #[wasm_bindgen] attribute
+  --> $DIR/invalid-attr.rs:21:5
+   |
+21 |     #[wasm_bindgen {  }]
+   |     ^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors
+

crates/macro/ui-tests/invalid-enums.rs

@@ -0,0 +1,23 @@
+#![feature(use_extern_macros)]
+
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+enum A {}
+
+#[wasm_bindgen]
+pub enum B {
+    D(u32),
+}
+
+#[wasm_bindgen]
+pub enum C {
+    X = 1 + 3,
+}
+
+#[wasm_bindgen]
+pub enum D {
+    X = 4294967296,
+}

crates/macro/ui-tests/invalid-enums.stderr

@@ -0,0 +1,26 @@
+error: only public enums are allowed with #[wasm_bindgen]
+ --> $DIR/invalid-enums.rs:8:1
+  |
+8 | enum A {}
+  | ^^^^^^^^^
+
+error: only C-Style enums allowed with #[wasm_bindgen]
+  --> $DIR/invalid-enums.rs:12:6
+   |
+12 |     D(u32),
+   |      ^^^^^
+
+error: enums with #[wasm_bidngen] may only have number literal values
+  --> $DIR/invalid-enums.rs:17:9
+   |
+17 |     X = 1 + 3,
+   |         ^^^^^
+
+error: enums with #[wasm_bindgen] can only support numbers that can be represented as u32
+  --> $DIR/invalid-enums.rs:22:9
+   |
+22 |     X = 4294967296,
+   |         ^^^^^^^^^^
+
+error: aborting due to 4 previous errors
+

crates/macro/ui-tests/invalid-imports.rs

@@ -0,0 +1,43 @@
+#![feature(use_extern_macros)]
+
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+extern "C" {
+    type A;
+
+    fn f() -> &'static u32;
+
+    #[wasm_bindgen(method)]
+    fn f1();
+    #[wasm_bindgen(method)]
+    fn f2(x: u32);
+    #[wasm_bindgen(method)]
+    fn f3(x: &&u32);
+    #[wasm_bindgen(method)]
+    fn f4(x: &foo::Bar);
+    #[wasm_bindgen(method)]
+    fn f4(x: &::Bar);
+    #[wasm_bindgen(method)]
+    fn f4(x: &Bar<T>);
+    #[wasm_bindgen(method)]
+    fn f4(x: &Fn(T));
+
+    #[wasm_bindgen(constructor)]
+    fn f();
+    #[wasm_bindgen(constructor)]
+    fn f() -> ::Bar;
+    #[wasm_bindgen(constructor)]
+    fn f() -> &Bar;
+
+    #[wasm_bindgen(catch)]
+    fn f() -> u32;
+    #[wasm_bindgen(catch)]
+    fn f() -> &u32;
+    #[wasm_bindgen(catch)]
+    fn f() -> Result<>;
+    #[wasm_bindgen(catch)]
+    fn f() -> Result<'a>;
+}

crates/macro/ui-tests/invalid-imports.stderr

@@ -0,0 +1,92 @@
+error: it is currently not sound to use lifetimes in function signatures
+  --> $DIR/invalid-imports.rs:11:16
+   |
+11 |     fn f() -> &'static u32;
+   |                ^^^^^^^
+
+error: imported methods must have at least one argument
+  --> $DIR/invalid-imports.rs:14:5
+   |
+14 |     fn f1();
+   |     ^^^^^^^^
+
+error: first argument of method must be a shared reference
+  --> $DIR/invalid-imports.rs:16:14
+   |
+16 |     fn f2(x: u32);
+   |              ^^^
+
+error: first argument of method must be a path
+  --> $DIR/invalid-imports.rs:18:14
+   |
+18 |     fn f3(x: &&u32);
+   |              ^^^^^
+
+error: multi-segment paths are not supported yet
+  --> $DIR/invalid-imports.rs:20:15
+   |
+20 |     fn f4(x: &foo::Bar);
+   |               ^^^^^^^^
+
+error: global paths are not supported yet
+  --> $DIR/invalid-imports.rs:22:15
+   |
+22 |     fn f4(x: &::Bar);
+   |               ^^^^^
+
+error: paths with type parameters are not supported yet
+  --> $DIR/invalid-imports.rs:24:15
+   |
+24 |     fn f4(x: &Bar<T>);
+   |               ^^^^^^
+
+error: paths with type parameters are not supported yet
+  --> $DIR/invalid-imports.rs:26:15
+   |
+26 |     fn f4(x: &Fn(T));
+   |               ^^^^^
+
+error: constructor returns must be bare types
+  --> $DIR/invalid-imports.rs:29:5
+   |
+29 |     fn f();
+   |     ^^^^^^^
+
+error: global paths are not supported yet
+  --> $DIR/invalid-imports.rs:31:15
+   |
+31 |     fn f() -> ::Bar;
+   |               ^^^^^
+
+error: return value of constructor must be a bare path
+  --> $DIR/invalid-imports.rs:33:5
+   |
+33 |     fn f() -> &Bar;
+   |     ^^^^^^^^^^^^^^^
+
+error: must be Result<...>
+  --> $DIR/invalid-imports.rs:36:15
+   |
+36 |     fn f() -> u32;
+   |               ^^^
+
+error: must be Result<...>
+  --> $DIR/invalid-imports.rs:38:15
+   |
+38 |     fn f() -> &u32;
+   |               ^^^^
+
+error: must have at least one generic parameter
+  --> $DIR/invalid-imports.rs:40:15
+   |
+40 |     fn f() -> Result<>;
+   |               ^^^^^^^^
+
+error: it is currently not sound to use lifetimes in function signatures
+  --> $DIR/invalid-imports.rs:42:22
+   |
+42 |     fn f() -> Result<'a>;
+   |                      ^^
+
+error: aborting due to 15 previous errors
+

crates/macro/ui-tests/invalid-items.rs

@@ -0,0 +1,38 @@
+#![feature(use_extern_macros)]
+
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+fn foo() {}
+
+#[wasm_bindgen]
+pub unsafe fn foo1() {}
+
+#[wasm_bindgen]
+pub const fn foo2() {}
+
+#[wasm_bindgen]
+struct Foo<T>(T);
+
+#[wasm_bindgen]
+extern "C" {
+    static mut FOO: u32;
+
+    pub fn foo3(x: i32, ...);
+}
+
+#[wasm_bindgen]
+extern "system" {
+}
+
+#[wasm_bindgen]
+pub fn foo4<T>() {}
+#[wasm_bindgen]
+pub fn foo5<'a>() {}
+#[wasm_bindgen]
+pub fn foo6<'a, T>() {}
+
+#[wasm_bindgen]
+trait X {}

crates/macro/ui-tests/invalid-items.stderr

@@ -0,0 +1,68 @@
+error: can only #[wasm_bindgen] public functions
+ --> $DIR/invalid-items.rs:8:1
+  |
+8 | fn foo() {}
+  | ^^^^^^^^^^^
+
+error: can only #[wasm_bindgen] safe functions
+  --> $DIR/invalid-items.rs:11:5
+   |
+11 | pub unsafe fn foo1() {}
+   |     ^^^^^^
+
+error: can only #[wasm_bindgen] non-const functions
+  --> $DIR/invalid-items.rs:14:5
+   |
+14 | pub const fn foo2() {}
+   |     ^^^^^
+
+error: structs with #[wasm_bindgen] cannot have lifetime or type parameters currently
+  --> $DIR/invalid-items.rs:17:11
+   |
+17 | struct Foo<T>(T);
+   |           ^^^
+
+error: cannot import mutable globals yet
+  --> $DIR/invalid-items.rs:21:12
+   |
+21 |     static mut FOO: u32;
+   |            ^^^
+
+error: can't #[wasm_bindgen] variadic functions
+  --> $DIR/invalid-items.rs:23:25
+   |
+23 |     pub fn foo3(x: i32, ...);
+   |                         ^^^
+
+error: only foreign mods with the `C` ABI are allowed
+  --> $DIR/invalid-items.rs:27:8
+   |
+27 | extern "system" {
+   |        ^^^^^^^^
+
+error: can't #[wasm_bindgen] functions with lifetime or type parameters
+  --> $DIR/invalid-items.rs:31:12
+   |
+31 | pub fn foo4<T>() {}
+   |            ^^^
+
+error: can't #[wasm_bindgen] functions with lifetime or type parameters
+  --> $DIR/invalid-items.rs:33:12
+   |
+33 | pub fn foo5<'a>() {}
+   |            ^^^^
+
+error: can't #[wasm_bindgen] functions with lifetime or type parameters
+  --> $DIR/invalid-items.rs:35:12
+   |
+35 | pub fn foo6<'a, T>() {}
+   |            ^^^^^^^
+
+error: #[wasm_bindgen] can only be applied to a function, struct, enum, impl, or extern block
+  --> $DIR/invalid-items.rs:38:1
+   |
+38 | trait X {}
+   | ^^^^^^^^^^
+
+error: aborting due to 11 previous errors
+

crates/macro/ui-tests/invalid-methods.rs

@@ -0,0 +1,43 @@
+#![feature(use_extern_macros)]
+
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+pub struct A;
+
+#[wasm_bindgen]
+default impl A {
+}
+
+#[wasm_bindgen]
+unsafe impl A {
+}
+
+#[wasm_bindgen]
+impl Clone for A {
+}
+
+#[wasm_bindgen]
+impl<T> A {
+}
+
+#[wasm_bindgen]
+impl &'static A {
+}
+
+macro_rules! x { () => () }
+
+#[wasm_bindgen]
+impl A {
+    const X: u32 = 3;
+    type Y = u32;
+    x!();
+
+    // pub default fn foo() {} // TODO: compiler's pretty printer totally broken
+
+
+    pub const fn foo() {}
+    pub unsafe fn foo() {}
+}

crates/macro/ui-tests/invalid-methods.stderr

@@ -0,0 +1,62 @@
+error: #[wasm_bindgen] default impls are not supported
+  --> $DIR/invalid-methods.rs:11:1
+   |
+11 | default impl A {
+   | ^^^^^^^
+
+error: #[wasm_bindgen] unsafe impls are not supported
+  --> $DIR/invalid-methods.rs:15:1
+   |
+15 | unsafe impl A {
+   | ^^^^^^
+
+error: #[wasm_bindgen] trait impls are not supported
+  --> $DIR/invalid-methods.rs:19:6
+   |
+19 | impl Clone for A {
+   |      ^^^^^
+
+error: #[wasm_bindgen] generic impls aren't supported
+  --> $DIR/invalid-methods.rs:23:5
+   |
+23 | impl<T> A {
+   |     ^^^
+
+error: unsupported self type in #[wasm_bindgen] impl
+  --> $DIR/invalid-methods.rs:27:6
+   |
+27 | impl &'static A {
+   |      ^^^^^^^^^^
+
+error: const definitions aren't supported with #[wasm_bindgen]
+  --> $DIR/invalid-methods.rs:34:5
+   |
+34 |     const X: u32 = 3;
+   |     ^^^^^^^^^^^^^^^^^
+
+error: type definitions in impls aren't supported with #[wasm_bindgen]
+  --> $DIR/invalid-methods.rs:35:5
+   |
+35 |     type Y = u32;
+   |     ^^^^^^^^^^^^^
+
+error: macros in impls aren't supported
+  --> $DIR/invalid-methods.rs:36:5
+   |
+36 |     x!();
+   |     ^^^^^
+
+error: can only #[wasm_bindgen] non-const functions
+  --> $DIR/invalid-methods.rs:41:9
+   |
+41 |     pub const fn foo() {}
+   |         ^^^^^
+
+error: can only bindgen safe functions
+  --> $DIR/invalid-methods.rs:42:9
+   |
+42 |     pub unsafe fn foo() {}
+   |         ^^^^^^
+
+error: aborting due to 10 previous errors
+

crates/macro/ui-tests/non-public-function.stderr

@@ -1,10 +1,8 @@
-error: custom attribute panicked
- --> $DIR/non-public-function.rs:7:1
+error: can only #[wasm_bindgen] public functions
+ --> $DIR/non-public-function.rs:8:1
   |
-7 | #[wasm_bindgen]
-  | ^^^^^^^^^^^^^^^
-  |
-  = help: message: can only bindgen public functions
+8 | fn foo() {}
+  | ^^^^^^^^^^^
 
 error: aborting due to previous error