Merge pull request #829 from rtfeldman/functions-in-repl

Functions in repl

cli/src/repl/eval.rs

@@ -20,6 +20,10 @@ struct Env<'a, 'env> {
     home: ModuleId,
 }
 
+pub enum ToAstProblem {
+    FunctionLayout,
+}
+
 /// JIT execute the given main function, and then wrap its results in an Expr
 /// so we can display them to the user using the formatter.
 ///
@@ -39,7 +43,7 @@ pub unsafe fn jit_to_ast<'a>(
     home: ModuleId,
     subs: &Subs,
     ptr_bytes: u32,
-) -> Expr<'a> {
+) -> Result<Expr<'a>, ToAstProblem> {
     let env = Env {
         arena,
         subs,
@@ -57,55 +61,57 @@ fn jit_to_ast_help<'a>(
     main_fn_name: &str,
     layout: &Layout<'a>,
     content: &Content,
-) -> Expr<'a> {
+) -> Result<Expr<'a>, ToAstProblem> {
     match layout {
-        Layout::Builtin(Builtin::Int1) => {
-            run_jit_function!(lib, main_fn_name, bool, |num| bool_to_ast(
-                env, num, content
-            ))
-        }
+        Layout::Builtin(Builtin::Int1) => Ok(run_jit_function!(lib, main_fn_name, bool, |num| {
+            bool_to_ast(env, num, content)
+        })),
         Layout::Builtin(Builtin::Int8) => {
+            Ok(
                 // NOTE: this is does not handle 8-bit numbers yet
-            run_jit_function!(lib, main_fn_name, u8, |num| byte_to_ast(env, num, content))
+                run_jit_function!(lib, main_fn_name, u8, |num| byte_to_ast(env, num, content)),
+            )
         }
         Layout::Builtin(Builtin::Int64) => {
-            run_jit_function!(lib, main_fn_name, i64, |num| num_to_ast(
+            Ok(run_jit_function!(lib, main_fn_name, i64, |num| num_to_ast(
                 env,
                 i64_to_ast(env.arena, num),
                 content
-            ))
+            )))
         }
         Layout::Builtin(Builtin::Float64) => {
-            run_jit_function!(lib, main_fn_name, f64, |num| num_to_ast(
+            Ok(run_jit_function!(lib, main_fn_name, f64, |num| num_to_ast(
                 env,
                 f64_to_ast(env.arena, num),
                 content
-            ))
+            )))
         }
-        Layout::Builtin(Builtin::Str) | Layout::Builtin(Builtin::EmptyStr) => {
+        Layout::Builtin(Builtin::Str) | Layout::Builtin(Builtin::EmptyStr) => Ok(
             run_jit_function!(lib, main_fn_name, &'static str, |string: &'static str| {
                 str_to_ast(env.arena, env.arena.alloc(string))
-            })
-        }
+            }),
+        ),
         Layout::Builtin(Builtin::EmptyList) => {
-            run_jit_function!(lib, main_fn_name, &'static str, |_| { Expr::List(&[]) })
+            Ok(run_jit_function!(lib, main_fn_name, &'static str, |_| {
+                Expr::List(&[])
+            }))
         }
-        Layout::Builtin(Builtin::List(_, elem_layout)) => run_jit_function!(
+        Layout::Builtin(Builtin::List(_, elem_layout)) => Ok(run_jit_function!(
             lib,
             main_fn_name,
             (*const u8, usize),
             |(ptr, len): (*const u8, usize)| { list_to_ast(env, ptr, len, elem_layout, content) }
-        ),
+        )),
         Layout::Builtin(other) => {
             todo!("add support for rendering builtin {:?} to the REPL", other)
         }
-        Layout::PhantomEmptyStruct => run_jit_function!(lib, main_fn_name, &u8, |_| {
+        Layout::PhantomEmptyStruct => Ok(run_jit_function!(lib, main_fn_name, &u8, |_| {
             Expr::Record {
                 update: None,
                 fields: &[],
                 final_comments: env.arena.alloc([]),
             }
-        }),
+        })),
         Layout::Struct(field_layouts) => {
             let ptr_to_ast = |ptr: *const u8| match content {
                 Content::Structure(FlatType::Record(fields, _)) => {
@@ -134,12 +140,12 @@ fn jit_to_ast_help<'a>(
 
             let result_stack_size = layout.stack_size(env.ptr_bytes);
 
-            run_jit_function_dynamic_type!(
+            Ok(run_jit_function_dynamic_type!(
                 lib,
                 main_fn_name,
                 result_stack_size as usize,
                 |bytes: *const u8| { ptr_to_ast(bytes as *const u8) }
-            )
+            ))
         }
         Layout::Union(union_layouts) => match content {
             Content::Structure(FlatType::TagUnion(tags, _)) => {
@@ -153,7 +159,7 @@ fn jit_to_ast_help<'a>(
                 let size = layout.stack_size(env.ptr_bytes);
                 match union_variant {
                     UnionVariant::Wrapped(tags_and_layouts) => {
-                        run_jit_function_dynamic_type!(
+                        Ok(run_jit_function_dynamic_type!(
                             lib,
                             main_fn_name,
                             size as usize,
@@ -181,7 +187,7 @@ fn jit_to_ast_help<'a>(
 
                                 Expr::Apply(loc_tag_expr, output, CalledVia::Space)
                             }
-                        )
+                        ))
                     }
                     _ => unreachable!("any other variant would have a different layout"),
                 }
@@ -201,7 +207,7 @@ fn jit_to_ast_help<'a>(
         }
 
         Layout::FunctionPointer(_, _) | Layout::Closure(_, _, _) => {
-            todo!("add support for rendering functions in the REPL")
+            Err(ToAstProblem::FunctionLayout)
         }
         Layout::Pointer(_) => todo!("add support for rendering pointers in the REPL"),
     }

cli/src/repl/gen.rs

@@ -131,11 +131,15 @@ pub fn gen_and_eval(src: &[u8], target: Triple, opt_level: OptLevel) -> Result<R
         let content = subs.get(main_fn_var).content;
         let expr_type_str = content_to_string(content.clone(), &subs, home, &interns);
 
-        let (_, main_fn_layout) = procedures
-            .keys()
-            .find(|(s, _)| *s == main_fn_symbol)
-            .unwrap()
-            .clone();
+        let (_, main_fn_layout) = match procedures.keys().find(|(s, _)| *s == main_fn_symbol) {
+            Some(layout) => layout.clone(),
+            None => {
+                return Ok(ReplOutput::NoProblems {
+                    expr: "<function>".to_string(),
+                    expr_type: expr_type_str,
+                });
+            }
+        };
 
         let ptr_bytes = target.pointer_width().unwrap().bytes() as u32;
 
@@ -249,7 +253,7 @@ pub fn gen_and_eval(src: &[u8], target: Triple, opt_level: OptLevel) -> Result<R
 
         let lib = module_to_dylib(&env.module, &target, opt_level)
             .expect("Error loading compiled dylib for test");
-        let answer = unsafe {
+        let res_answer = unsafe {
             eval::jit_to_ast(
                 &arena,
                 lib,
@@ -264,7 +268,15 @@ pub fn gen_and_eval(src: &[u8], target: Triple, opt_level: OptLevel) -> Result<R
         };
         let mut expr = bumpalo::collections::String::new_in(&arena);
 
+        use eval::ToAstProblem::*;
+        match res_answer {
+            Ok(answer) => {
                 answer.format_with_options(&mut expr, Parens::NotNeeded, Newlines::Yes, 0);
+            }
+            Err(FunctionLayout) => {
+                expr.push_str("<function>");
+            }
+        }
 
         Ok(ReplOutput::NoProblems {
             expr: expr.into_bump_str().to_string(),

cli/tests/repl_eval.rs

@@ -462,6 +462,40 @@ mod repl_eval {
         );
     }
 
+    #[test]
+    fn identity_lambda() {
+        // Even though this gets unwrapped at runtime, the repl should still
+        // report it as a record
+        expect_success("\\x -> x", "<function> : a -> a");
+    }
+
+    #[test]
+    fn stdlib_function() {
+        // Even though this gets unwrapped at runtime, the repl should still
+        // report it as a record
+        expect_success("Num.abs", "<function> : Num a -> Num a");
+    }
+
+    #[test]
+    fn too_few_args() {
+        expect_failure(
+            "Num.add 2",
+            indoc!(
+                r#"
+                ── TOO FEW ARGS ────────────────────────────────────────────────────────────────
+
+                The add function expects 2 arguments, but it got only 1:
+
+                4│      Num.add 2
+                        ^^^^^^^
+
+                Roc does not allow functions to be partially applied. Use a closure to
+                make partial application explicit.
+                "#
+            ),
+        );
+    }
+
     #[test]
     fn type_problem() {
         expect_failure(

compiler/load/src/file.rs

@@ -20,7 +20,7 @@ use roc_module::symbol::{
 use roc_mono::ir::{
     CapturedSymbols, ExternalSpecializations, PartialProc, PendingSpecialization, Proc, Procs,
 };
-use roc_mono::layout::{Layout, LayoutCache};
+use roc_mono::layout::{Layout, LayoutCache, LayoutProblem};
 use roc_parse::ast::{self, Attempting, StrLiteral, TypeAnnotation};
 use roc_parse::header::{
     ExposesEntry, ImportsEntry, PackageEntry, PackageOrPath, PlatformHeader, To, TypedIdent,
@@ -3508,9 +3508,20 @@ fn add_def_to_module<'a>(
                             mono_env.subs,
                         ) {
                             Ok(l) => l,
-                            Err(err) => {
-                                // a host-exposed function is not monomorphized
-                                todo!("The host-exposed function {:?} does not have a valid layout (e.g. maybe the function wasn't monomorphic): {:?}", symbol, err)
+                            Err(LayoutProblem::Erroneous) => {
+                                let message = "top level function has erroneous type";
+                                procs.runtime_errors.insert(symbol, message);
+                                return;
+                            }
+                            Err(LayoutProblem::UnresolvedTypeVar(v)) => {
+                                let message = format!(
+                                    "top level function has unresolved type variable {:?}",
+                                    v
+                                );
+                                procs
+                                    .runtime_errors
+                                    .insert(symbol, mono_env.arena.alloc(message));
+                                return;
                             }
                         };
 
@@ -3542,9 +3553,29 @@ fn add_def_to_module<'a>(
                     // get specialized!
                     if is_exposed {
                         let annotation = def.expr_var;
-                        let layout = layout_cache.from_var(mono_env.arena, annotation, mono_env.subs).unwrap_or_else(|err|
-                                        todo!("TODO gracefully handle the situation where we expose a function to the host which doesn't have a valid layout (e.g. maybe the function wasn't monomorphic): {:?}", err)
+
+                        let layout = match layout_cache.from_var(
+                            mono_env.arena,
+                            annotation,
+                            mono_env.subs,
+                        ) {
+                            Ok(l) => l,
+                            Err(LayoutProblem::Erroneous) => {
+                                let message = "top level function has erroneous type";
+                                procs.runtime_errors.insert(symbol, message);
+                                return;
+                            }
+                            Err(LayoutProblem::UnresolvedTypeVar(v)) => {
+                                let message = format!(
+                                    "top level function has unresolved type variable {:?}",
+                                    v
                                 );
+                                procs
+                                    .runtime_errors
+                                    .insert(symbol, mono_env.arena.alloc(message));
+                                return;
+                            }
+                        };
 
                         procs.insert_exposed(
                             symbol,

compiler/mono/src/ir.rs

@@ -1508,7 +1508,6 @@ pub fn specialize_all<'a>(
                         ));
 
                         procs.runtime_errors.insert(name, error_msg);
-                        panic!("failed to specialize {:?}", name);
                     }
                 }
             }
@@ -4869,9 +4868,7 @@ fn reuse_function_symbol<'a>(
             // this symbol is a function, that is used by-name (e.g. as an argument to another
             // function). Register it with the current variable, then create a function pointer
             // to it in the IR.
-            let layout = layout_cache
-                .from_var(env.arena, arg_var, env.subs)
-                .expect("creating layout does not fail");
+            let res_layout = layout_cache.from_var(env.arena, arg_var, env.subs);
 
             // we have three kinds of functions really. Plain functions, closures by capture,
             // and closures by unification. Here we record whether this function captures
@@ -4879,8 +4876,8 @@ fn reuse_function_symbol<'a>(
             let captures = partial_proc.captured_symbols.captures();
             let captured = partial_proc.captured_symbols.clone();
 
-            match layout {
-                Layout::Closure(argument_layouts, closure_layout, ret_layout) if captures => {
+            match res_layout {
+                Ok(Layout::Closure(argument_layouts, closure_layout, ret_layout)) if captures => {
                     // this is a closure by capture, meaning it itself captures local variables.
                     // we've defined the closure as a (function_ptr, closure_data) pair already
 
@@ -4958,7 +4955,7 @@ fn reuse_function_symbol<'a>(
 
                     stmt
                 }
-                _ => {
+                Ok(layout) => {
                     procs.insert_passed_by_name(
                         env,
                         arg_var,
@@ -4974,6 +4971,17 @@ fn reuse_function_symbol<'a>(
                         env.arena.alloc(result),
                     )
                 }
+                Err(LayoutProblem::Erroneous) => {
+                    let message = format!("The {:?} symbol has an erroneous type", symbol);
+                    Stmt::RuntimeError(env.arena.alloc(message))
+                }
+                Err(LayoutProblem::UnresolvedTypeVar(v)) => {
+                    let message = format!(
+                        "The {:?} symbol contains a unresolved type var {:?}",
+                        symbol, v
+                    );
+                    Stmt::RuntimeError(env.arena.alloc(message))
+                }
             }
         }
     }