fix: Unify macro result type with actual type

compiler/noirc_frontend/src/elaborator/expressions.rs

@@ -478,7 +478,17 @@ impl<'context> Elaborator<'context> {
 
                 // Type check the new call now that it has been changed from a method call
                 // to a function call. This way we avoid duplicating code.
-                let typ = self.type_check_call(&function_call, func_type, function_args, span);
+                let mut typ = self.type_check_call(&function_call, func_type, function_args, span);
+                if is_macro_call {
+                    if self.in_comptime_context() {
+                        typ = self.interner.next_type_variable();
+                    } else {
+                        let args = function_call.arguments.clone();
+                        return self
+                            .call_macro(function_call.func, args, location, typ)
+                            .unwrap_or_else(|| (HirExpression::Error, Type::Error));
+                    }
+                }
                 (HirExpression::Call(function_call), typ)
             }
             None => (HirExpression::Error, Type::Error),

compiler/noirc_frontend/src/elaborator/mod.rs

@@ -97,7 +97,7 @@ pub struct Elaborator<'context> {
 
     def_maps: &'context mut DefMaps,
 
-    file: FileId,
+    pub(crate) file: FileId,
 
     in_unsafe_block: bool,
     nested_loops: usize,

compiler/noirc_frontend/src/elaborator/types.rs

@@ -710,7 +710,7 @@ impl<'context> Elaborator<'context> {
         }
     }
 
-    pub(super) fn unify(
+    pub fn unify(
         &mut self,
         actual: &Type,
         expected: &Type,

compiler/noirc_frontend/src/hir/comptime/interpreter.rs

@@ -12,6 +12,7 @@
 use crate::elaborator::Elaborator;
 use crate::graph::CrateId;
 use crate::hir::def_map::ModuleId;
+use crate::hir::type_check::TypeCheckError;
 use crate::hir_def::expr::ImplKind;
 use crate::hir_def::function::FunctionBody;
 use crate::macros_api::UnaryOp;
@@ -242,7 +243,7 @@
             }
         } else {
             let name = self.elaborator.interner.function_name(&function);
             unreachable!("Non-builtin, lowlevel or oracle builtin fn '{name}'")
         }
     }
 
@@ -1298,6 +1299,13 @@
                         elaborator.elaborate_expression(expr).0
                     });
                     result = self.evaluate(expr)?;
+
+                    // Macro calls are typed as type variables during type checking.
+                    // Now that we know the type we need to further unify it in case there
+                    // are inconsistencies or the type needs to be known.
+                    let expected_type = self.elaborator.interner.id_type(id);
+                    let actual_type = result.get_type();
+                    self.unify(&actual_type, &expected_type, location);
                 }
                 Ok(result)
             }
@@ -1311,6 +1319,18 @@
         }
     }
 
+    fn unify(&mut self, actual: &Type, expected: &Type, location: Location) {
+        // We need to swap out the elaborator's file since we may be
+        // in a different one currently, and it uses that for the error location.
+        let old_file = std::mem::replace(&mut self.elaborator.file, location.file);
+        self.elaborator.unify(actual, expected, || TypeCheckError::TypeMismatch {
+            expected_typ: expected.to_string(),
+            expr_typ: actual.to_string(),
+            expr_span: location.span,
+        });
+        self.elaborator.file = old_file;
+    }
+
     fn evaluate_method_call(
         &mut self,
         call: HirMethodCallExpression,

noir_stdlib/src/meta/mod.nr

@@ -130,8 +130,13 @@ mod tests {
             // let _a: Quoted = quote { 1 };
             let _a: Quoted = quote_one();
 
-            // let _b: i32 = 1;
-            let _b: i32 = quote_one!();
+            // let _b: Field = 1;
+            let _b: Field = quote_one!();
+
+            // Since integers default to fields, if we
+            // want a different type we have to explicitly cast
+            // let _c: i32 = 1 as i32;
+            let _c: i32 = quote_one!() as i32;
         }
     }
     // docs:end:quote-example

test_programs/compile_success_empty/macro_result_type/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "macro_result_type"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.34.0"
+
+[dependencies]

test_programs/compile_success_empty/macro_result_type/src/main.nr

@@ -0,0 +1,13 @@
+fn main() {
+    comptime
+    {
+        let signature = "hello".as_ctstring();
+        let string = signature.as_quoted_str!();
+        let result = half(string);
+        assert_eq(result, 2);
+    }
+}
+
+comptime fn half<let N: u32>(_s: str<N>) -> u32 {
+    N / 2
+}

test_programs/compile_success_empty/macro_result_type/t.rs

@@ -0,0 +1,12 @@
+
+trait Foo<const N: u32> {
+    fn foo() {}
+}
+
+impl Foo<3> for () {
+    fn foo() {}
+}
+
+fn main() {
+    let _ = Foo::foo();
+}