add Expect ir::Stmt node

compiler/alias_analysis/src/lib.rs

@@ -439,6 +439,7 @@ fn stmt_spec<'a>(
 
             builder.add_choice(block, &cases)
         }
+        Expect { remainder, .. } => stmt_spec(builder, env, block, layout, remainder),
         Ret(symbol) => Ok(env.symbols[symbol]),
         Refcounting(modify_rc, continuation) => match modify_rc {
             ModifyRc::Inc(symbol, _) => {

compiler/gen_dev/src/lib.rs

@@ -979,6 +979,9 @@ trait Backend<'a> {
                     self.set_last_seen(*sym, stmt);
                 }
             }
+
+            Stmt::Expect { .. } => todo!("expect is not implemented in the wasm backend"),
+
             Stmt::RuntimeError(_) => {}
         }
     }

compiler/gen_llvm/src/llvm/build.rs

@@ -2737,6 +2737,80 @@ pub fn build_exp_stmt<'a, 'ctx, 'env>(
             }
         }
 
+        Expect {
+            condition: cond,
+            lookups: _,
+            layouts: _,
+            remainder,
+        } => {
+            // do stuff
+
+            let bd = env.builder;
+            let context = env.context;
+
+            let (cond, _cond_layout) = load_symbol_and_layout(scope, cond);
+
+            let condition = bd.build_int_compare(
+                IntPredicate::EQ,
+                cond.into_int_value(),
+                context.bool_type().const_int(1, false),
+                "is_true",
+            );
+
+            let then_block = context.append_basic_block(parent, "then_block");
+            let throw_block = context.append_basic_block(parent, "throw_block");
+
+            bd.build_conditional_branch(condition, then_block, throw_block);
+
+            {
+                bd.position_at_end(throw_block);
+
+                match env.target_info.ptr_width() {
+                    roc_target::PtrWidth::Bytes8 => {
+                        let func = env
+                            .module
+                            .get_function(bitcode::UTILS_EXPECT_FAILED)
+                            .unwrap();
+                        // TODO get the actual line info instead of
+                        // hardcoding as zero!
+                        let callable = CallableValue::try_from(func).unwrap();
+                        let start_line = context.i32_type().const_int(0, false);
+                        let end_line = context.i32_type().const_int(0, false);
+                        let start_col = context.i16_type().const_int(0, false);
+                        let end_col = context.i16_type().const_int(0, false);
+
+                        bd.build_call(
+                            callable,
+                            &[
+                                start_line.into(),
+                                end_line.into(),
+                                start_col.into(),
+                                end_col.into(),
+                            ],
+                            "call_expect_failed",
+                        );
+
+                        bd.build_unconditional_branch(then_block);
+                    }
+                    roc_target::PtrWidth::Bytes4 => {
+                        // temporary WASM implementation
+                        throw_exception(env, "An expectation failed!");
+                    }
+                }
+            }
+
+            bd.position_at_end(then_block);
+
+            build_exp_stmt(
+                env,
+                layout_ids,
+                func_spec_solutions,
+                scope,
+                parent,
+                remainder,
+            )
+        }
+
         RuntimeError(error_msg) => {
             throw_exception(env, error_msg);
 
@@ -6128,8 +6202,6 @@ fn run_low_level<'a, 'ctx, 'env>(
             set
         }
         ExpectTrue => {
-            debug_assert_eq!(args.len(), 1);
-
             let context = env.context;
             let bd = env.builder;
 

compiler/gen_wasm/src/backend.rs

@@ -457,6 +457,8 @@ impl<'a> WasmBackend<'a> {
 
             Stmt::Refcounting(modify, following) => self.stmt_refcounting(modify, following),
 
+            Stmt::Expect { .. } => todo!("expect is not implemented in the wasm backend"),
+
             Stmt::RuntimeError(msg) => self.stmt_runtime_error(msg),
         }
     }

compiler/mono/src/borrow.rs

@@ -307,6 +307,9 @@ impl<'a> ParamMap<'a> {
                 Let(_, _, _, cont) => {
                     stack.push(cont);
                 }
+
+                Expect { remainder, .. } => stack.push(remainder),
+
                 Switch {
                     branches,
                     default_branch,
@@ -835,6 +838,11 @@ impl<'a> BorrowInfState<'a> {
                 }
                 self.collect_stmt(param_map, default_branch.1);
             }
+
+            Expect { remainder, .. } => {
+                self.collect_stmt(param_map, remainder);
+            }
+
             Refcounting(_, _) => unreachable!("these have not been introduced yet"),
 
             Ret(_) | RuntimeError(_) => {
@@ -1027,6 +1035,9 @@ fn call_info_stmt<'a>(arena: &'a Bump, stmt: &Stmt<'a>, info: &mut CallInfo<'a>)
                 stack.extend(branches.iter().map(|b| &b.2));
                 stack.push(default_branch.1);
             }
+
+            Expect { remainder, .. } => stack.push(remainder),
+
             Refcounting(_, _) => unreachable!("these have not been introduced yet"),
 
             Ret(_) | Jump(_, _) | RuntimeError(_) => {

compiler/mono/src/inc_dec.rs

@@ -108,6 +108,15 @@ pub fn occurring_variables(stmt: &Stmt<'_>) -> (MutSet<Symbol>, MutSet<Symbol>)
                 stack.push(cont);
             }
 
+            Expect {
+                condition,
+                remainder,
+                ..
+            } => {
+                result.insert(*condition);
+                stack.push(remainder);
+            }
+
             Jump(_, arguments) => {
                 result.extend(arguments.iter().copied());
             }
@@ -1196,6 +1205,8 @@ impl<'a> Context<'a> {
                 (switch, case_live_vars)
             }
 
+            Expect { remainder, .. } => self.visit_stmt(codegen, remainder),
+
             RuntimeError(_) | Refcounting(_, _) => (stmt, MutSet::default()),
         }
     }
@@ -1299,6 +1310,15 @@ pub fn collect_stmt(
             collect_stmt(cont, jp_live_vars, vars)
         }
 
+        Expect {
+            condition,
+            remainder,
+            ..
+        } => {
+            vars.insert(*condition);
+            collect_stmt(remainder, jp_live_vars, vars)
+        }
+
         Join {
             id: j,
             parameters,

compiler/mono/src/ir.rs

@@ -1326,6 +1326,13 @@ pub enum Stmt<'a> {
     },
     Ret(Symbol),
     Refcounting(ModifyRc, &'a Stmt<'a>),
+    Expect { 
+        condition: Symbol,
+        lookups: &'a [Symbol], 
+        layouts: &'a [Layout<'a>],
+        /// what happens after the expect 
+        remainder: &'a Stmt<'a>,
+    },
     /// a join point `join f <params> = <continuation> in remainder`
     Join {
         id: JoinPointId,
@@ -1912,6 +1919,10 @@ impl<'a> Stmt<'a> {
                 .append(alloc.hardline())
                 .append(cont.to_doc(alloc)),
 
+            Expect{condition, .. }  => 
+                alloc.text("expect ")
+                .append(symbol_to_doc(alloc, *condition)),
+
             Ret(symbol) => alloc
                 .text("ret ")
                 .append(symbol_to_doc(alloc, *symbol))
@@ -5931,22 +5942,20 @@ pub fn from_can<'a>(
         Expect {
             loc_condition,
             loc_continuation,
-            lookups_in_cond: _ ,
+            lookups_in_cond,
         } => {
             let rest = from_can(env, variable, loc_continuation.value, procs, layout_cache);
             let cond_symbol = env.unique_symbol();
-            let mut stmt = Stmt::Let(
+
-                env.unique_symbol(),
+            let lookups = Vec::from_iter_in(lookups_in_cond.iter().map(|t| t.0), env.arena);
-                Expr::Call(self::Call {
+            // let layouts = Vec::from_iter_in(lookups_in_cond.iter().map(|t| t.1), env.arena);
-                    call_type: CallType::LowLevel {
+
-                        op: LowLevel::ExpectTrue,
+            let mut stmt = Stmt::Expect {
-                        update_mode: env.next_update_mode_id(),
+                condition: cond_symbol,
-                    },
+                lookups: lookups.into_bump_slice(),
-                    arguments: env.arena.alloc([cond_symbol]),
+                layouts: &[],
-                }),
+                remainder: env.arena.alloc(rest),
-                Layout::Builtin(Builtin::Bool),
+            };
-                env.arena.alloc(rest),
-            );
 
             stmt = with_hole(
                 env,
@@ -5958,7 +5967,6 @@ pub fn from_can<'a>(
                 env.arena.alloc(stmt),
             );
 
-
             stmt
         }
 
@@ -6300,6 +6308,14 @@ fn substitute_in_stmt_help<'a>(
             }
         }
 
+        Expect { condition, lookups, layouts, remainder } => {  
+            // TODO should we substitute in the ModifyRc?
+            match substitute_in_stmt_help(arena, remainder, subs) {
+                Some(cont) => Some(arena.alloc(Expect { condition: *condition , lookups, layouts, remainder: cont} )),
+                None => None,
+            }
+        }
+
         Jump(id, args) => {
             let mut did_change = false;
             let new_args = Vec::from_iter_in(

compiler/mono/src/reset_reuse.rs

@@ -192,6 +192,30 @@ fn function_s<'a, 'i>(
                 arena.alloc(new_refcounting)
             }
         }
+
+        Expect {
+            condition,
+            lookups,
+            layouts,
+            remainder,
+        } => {
+            let continuation: &Stmt = *remainder;
+            let new_continuation = function_s(env, w, c, continuation);
+
+            if std::ptr::eq(continuation, new_continuation) || continuation == new_continuation {
+                stmt
+            } else {
+                let new_refcounting = Expect {
+                    condition: *condition,
+                    lookups,
+                    layouts,
+                    remainder: new_continuation,
+                };
+
+                arena.alloc(new_refcounting)
+            }
+        }
+
         Ret(_) | Jump(_, _) | RuntimeError(_) => stmt,
     }
 }
@@ -388,6 +412,37 @@ fn function_d_main<'a, 'i>(
                 (arena.alloc(refcounting), found)
             }
         }
+
+        Expect {
+            condition,
+            lookups,
+            layouts,
+            remainder,
+        } => {
+            let (b, found) = function_d_main(env, x, c, remainder);
+
+            if found || *condition != x {
+                let refcounting = Expect {
+                    condition: *condition,
+                    lookups,
+                    layouts,
+                    remainder: b,
+                };
+
+                (arena.alloc(refcounting), found)
+            } else {
+                let b = try_function_s(env, x, c, b);
+
+                let refcounting = Expect {
+                    condition: *condition,
+                    lookups,
+                    layouts,
+                    remainder: b,
+                };
+
+                (arena.alloc(refcounting), found)
+            }
+        }
         Join {
             id,
             parameters,
@@ -540,6 +595,24 @@ fn function_r<'a, 'i>(env: &mut Env<'a, 'i>, stmt: &'a Stmt<'a>) -> &'a Stmt<'a>
             arena.alloc(Refcounting(*modify_rc, b))
         }
 
+        Expect {
+            condition,
+            lookups,
+            layouts,
+            remainder,
+        } => {
+            let b = function_r(env, remainder);
+
+            let expect = Expect {
+                condition: *condition,
+                lookups,
+                layouts,
+                remainder: b,
+            };
+
+            arena.alloc(expect)
+        }
+
         Ret(_) | Jump(_, _) | RuntimeError(_) => {
             // terminals
             stmt
@@ -570,6 +643,11 @@ fn has_live_var<'a>(jp_live_vars: &JPLiveVarMap, stmt: &'a Stmt<'a>, needle: Sym
         Refcounting(modify_rc, cont) => {
             modify_rc.get_symbol() == needle || has_live_var(jp_live_vars, cont, needle)
         }
+        Expect {
+            condition,
+            remainder,
+            ..
+        } => *condition == needle || has_live_var(jp_live_vars, remainder, needle),
         Join {
             id,
             parameters,

compiler/mono/src/tail_recursion.rs

@@ -191,6 +191,21 @@ fn insert_jumps<'a>(
             None => None,
         },
 
+        Expect {
+            condition,
+            lookups,
+            layouts,
+            remainder,
+        } => match insert_jumps(arena, remainder, goal_id, needle) {
+            Some(cont) => Some(arena.alloc(Expect {
+                condition: *condition,
+                lookups,
+                layouts,
+                remainder: cont,
+            })),
+            None => None,
+        },
+
         Ret(_) => None,
         Jump(_, _) => None,
         RuntimeError(_) => None,

examples/hello-world/zig-platform/helloZig.roc

@@ -3,4 +3,8 @@ app "helloZig"
     imports []
     provides [main] to pf
 
-main = "Hello, World!\n"
+x = 42
+
+main = 
+    expect x != x
+    "Hello, World!\n"