Graceful error for wrong number of activities

Added graceful error message instead of an ICE
Blessed tests

Author: vayunbiyani

tests/ui/autodiff/autodiff_illegal.rs

@@ -30,16 +30,22 @@ pub fn f4(x: f64) {
     unimplemented!()
 }
 
+#[autodiff(df5, Forward, Dual, Dual)]
+fn f5(x: f32, y: f32) -> f32 {
+    // ~^^ error: expected 3 activities, but found 2
+    x+y
+}
+
 // We can't use Dual in Reverse mode
-#[autodiff(df5, Reverse, Dual)]
-pub fn f5(x: f64) {
+#[autodiff(df6, Reverse, Dual)]
+pub fn f6(x: f64) {
     //~^^ ERROR     Dual can not be used in Reverse Mode
     unimplemented!()
 }
 
 // We can't use Duplicated in Forward mode
-#[autodiff(df6, Forward, Duplicated)]
-pub fn f6(x: f64) {
+#[autodiff(df7, Forward, Duplicated)]
+pub fn f7(x: f64) {
     //~^^ ERROR Duplicated can not be used in Forward Mode
     //~^^ ERROR Duplicated can not be used for this type
     unimplemented!()
@@ -62,52 +68,52 @@ fn dummy() {
 
 // Malformed, where args?
 #[autodiff]
-pub fn f7(x: f64) {
-    //~^ ERROR autodiff requires at least a name and mode
+pub fn f8(x: f64) {
+    //~^ ERROR autodiff must be applied to function
     unimplemented!()
 }
 
 // Malformed, where args?
 #[autodiff()]
-pub fn f8(x: f64) {
+pub fn f9(x: f64) {
     //~^ ERROR autodiff requires at least a name and mode
     unimplemented!()
 }
 
 // Invalid attribute syntax
 #[autodiff = ""]
-pub fn f9(x: f64) {
-    //~^ ERROR autodiff requires at least a name and mode
+pub fn f10(x: f64) {
+    //~^ ERROR autodiff must be applied to function
     unimplemented!()
 }
 
 fn fn_exists() {}
 
 // We colide with an already existing function
 #[autodiff(fn_exists, Reverse, Active)]
-pub fn f10(x: f64) {
+pub fn f11(x: f64) {
     //~^^ ERROR the name `fn_exists` is defined multiple times [E0428]
     unimplemented!()
 }
 
 // Malformed, missing a mode
-#[autodiff(df11)]
-pub fn f11() {
+#[autodiff(df12)]
+pub fn f12() {
     //~^ ERROR autodiff requires at least a name and mode
     unimplemented!()
 }
 
 // Invalid Mode
-#[autodiff(df12, Debug)]
-pub fn f12() {
+#[autodiff(df13, Debug)]
+pub fn f13() {
     //~^^ ERROR unknown Mode: `Debug`. Use `Forward` or `Reverse`
     unimplemented!()
 }
 
 // Invalid, please pick one Mode
 // or use two autodiff macros.
-#[autodiff(df13, Forward, Reverse)]
-pub fn f13() {
+#[autodiff(df14, Forward, Reverse)]
+pub fn f14() {
     //~^^ ERROR did not recognize Activity: `Reverse`
     unimplemented!()
 }
@@ -117,8 +123,8 @@ struct Foo {}
 // We can't handle Active structs, because that would mean (in the general case), that we would
 // need to allocate and initialize arbitrary user types. We have Duplicated/Dual input args for
 // that. FIXME: Give a nicer error and suggest to the user to have a `&mut Foo` input instead.
-#[autodiff(df14, Reverse, Active, Active)]
-fn f14(x: f32) -> Foo {
+#[autodiff(df15, Reverse, Active, Active)]
+fn f15(x: f32) -> Foo {
     unimplemented!()
 }
 
@@ -127,15 +133,15 @@ type MyFloat = f32;
 // We would like to support type alias to f32/f64 in argument type in the future,
 // but that requires us to implement our checks at a later stage
 // like THIR which has type information available.
-#[autodiff(df15, Reverse, Active, Active)]
-fn f15(x: MyFloat) -> f32 {
+#[autodiff(df16, Reverse, Active, Active)]
+fn f16(x: MyFloat) -> f32 {
     //~^^ ERROR failed to resolve: use of undeclared type `MyFloat` [E0433]
     unimplemented!()
 }
 
 // We would like to support type alias to f32/f64 in return type in the future
-#[autodiff(df16, Reverse, Active, Active)]
-fn f16(x: f32) -> MyFloat {
+#[autodiff(df17, Reverse, Active, Active)]
+fn f17(x: f32) -> MyFloat {
     unimplemented!()
 }
 
@@ -145,34 +151,34 @@ struct F64Trans {
 }
 
 // We would like to support `#[repr(transparent)]` f32/f64 wrapper in return type in the future
-#[autodiff(df17, Reverse, Active, Active)]
-fn f17(x: f64) -> F64Trans {
+#[autodiff(df18, Reverse, Active, Active)]
+fn f18(x: f64) -> F64Trans {
     unimplemented!()
 }
 
 // We would like to support `#[repr(transparent)]` f32/f64 wrapper in argument type in the future
-#[autodiff(df18, Reverse, Active, Active)]
-fn f18(x: F64Trans) -> f64 {
+#[autodiff(df19, Reverse, Active, Active)]
+fn f19(x: F64Trans) -> f64 {
     //~^^ ERROR failed to resolve: use of undeclared type `F64Trans` [E0433]
     unimplemented!()
 }
 
 // Invalid return activity
-#[autodiff(df19, Forward, Dual, Active)]
-fn f19(x: f32) -> f32 {
+#[autodiff(df20, Forward, Dual, Active)]
+fn f20(x: f32) -> f32 {
     //~^^ ERROR invalid return activity Active in Forward Mode
     unimplemented!()
 }
 
 #[autodiff(df20, Reverse, Active, Dual)]
-fn f20(x: f32) -> f32 {
+fn f21(x: f32) -> f32 {
     //~^^ ERROR invalid return activity Dual in Reverse Mode
     unimplemented!()
 }
 
 // Duplicated cannot be used as return activity
 #[autodiff(df21, Reverse, Active, Duplicated)]
-fn f21(x: f32) -> f32 {
+fn f22(x: f32) -> f32 {
     //~^^ ERROR invalid return activity Duplicated in Reverse Mode
     unimplemented!()
 }

tests/ui/autodiff/autodiff_illegal.stderr

@@ -139,6 +139,12 @@ error: invalid return activity Duplicated in Reverse Mode
 LL | #[autodiff(df21, Reverse, Active, Duplicated)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+error: expected 3 activities, but found 2
+  --> $DIR/autodiff_illegal.rs:180:1
+   |
+LL | #[autodiff(df, Forward, Dual, Dual)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0433]: failed to resolve: use of undeclared type `MyFloat`
   --> $DIR/autodiff_illegal.rs:130:1
    |
@@ -151,6 +157,20 @@ error[E0433]: failed to resolve: use of undeclared type `F64Trans`
 LL | #[autodiff(df18, Reverse, Active, Active)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ use of undeclared type `F64Trans`
 
+error[E0308]: mismatched types
+  --> $DIR/autodiff_illegal.rs:181:25
+   |
+LL | #[autodiff(df, Forward, Dual, Dual)]
+   |            -- implicitly returns `()` as its body has no tail or `return` expression
+LL | fn f(x: f32, y: f32) -> f32 {
+   |                         ^^^ expected `f32`, found `()`
+   |
+note: consider returning one of these bindings
+  --> $DIR/autodiff_illegal.rs:181:6
+   |
+LL | fn f(x: f32, y: f32) -> f32 {
+   |      ^       ^
+
 error[E0599]: the function or associated item `default` exists for tuple `(DoesNotImplDefault, DoesNotImplDefault)`, but its trait bounds were not satisfied
   --> $DIR/autodiff_illegal.rs:181:1
    |
@@ -168,7 +188,7 @@ LL + #[derive(Default)]
 LL | struct DoesNotImplDefault;
    |
 
-error: aborting due to 23 previous errors
+error: aborting due to 22 previous errors
 
-Some errors have detailed explanations: E0428, E0433, E0599, E0658.
+Some errors have detailed explanations: E0428, E0433, E0658.
 For more information about an error, try `rustc --explain E0428`.