Fix checked interpolation default reachability

Author: rtfeldman

src/check/checked_artifact.zig

@@ -80,13 +80,29 @@ pub const ModuleEnvStorage = union(enum) {
     }
 };
 
-fn moduleExprIsBuiltinStr(module: TypedCIR.Module, expr_idx: CIR.Expr.Idx) bool {
+fn moduleExprUsesBuiltinStrInterpolationPath(module: TypedCIR.Module, expr_idx: CIR.Expr.Idx) bool {
     const resolved = module.typeStoreConst().resolveVar(module.exprType(expr_idx));
-    const nominal = resolved.desc.content.unwrapNominalType() orelse return false;
-    if (!nominal.originIsBuiltin()) return false;
-    const ident = nominal.ident.ident_idx;
-    const common = module.commonIdents();
-    return ident.eql(common.str) or ident.eql(common.builtin_str);
+    switch (resolved.desc.content) {
+        .structure => |flat_type| {
+            if (flat_type != .nominal_type) return false;
+            const nominal = flat_type.nominal_type;
+            if (!nominal.originIsBuiltin()) return false;
+            const ident = nominal.ident.ident_idx;
+            const common = module.commonIdents();
+            return ident.eql(common.str) or ident.eql(common.builtin_str);
+        },
+        .flex => |flex| {
+            const phase = numericDefaultPhaseForFlex(module, flex) orelse return false;
+            return phase == .mono_specialization_str;
+        },
+        .rigid => |rigid| {
+            const phase = numericDefaultPhaseForConstraints(module, rigid.constraints) orelse return false;
+            return phase == .mono_specialization_str;
+        },
+        .alias,
+        .err,
+        => return false,
+    }
 }
 
 /// Public `CheckedModuleArtifactKey` declaration.
@@ -1454,7 +1470,8 @@ pub const NumericDefaultPhase = enum {
     /// Defaults to Dec when still unresolved at monomorphic specialization.
     mono_specialization,
     /// Defaults to Str when still unresolved at monomorphic specialization
-    /// (string literals carrying a from_quote constraint).
+    /// (string literals carrying a from_quote constraint, and interpolated
+    /// string literals carrying a from_interpolation constraint).
     mono_specialization_str,
 };
 
@@ -5414,7 +5431,7 @@ const CheckedSourceNodes = struct {
             .e_interpolation => |interpolation| {
                 try self.markExpr(interpolation.first, work);
                 try self.markExprSpan(module, interpolation.parts, work);
-                if (!moduleExprIsBuiltinStr(module, expr_idx)) {
+                if (!moduleExprUsesBuiltinStrInterpolationPath(module, expr_idx)) {
                     try self.markExpr(interpolation.rest, work);
                 }
             },

src/cli/test/parallel_cli_runner.zig

@@ -618,6 +618,7 @@ const subcommand_cases = [_]CliCase{
     .{ .id = 0, .suite = .subcommands, .name = "roc check succeeds with unused app package shorthand (issue 9488)", .body = .{ .command = .{ .args = &.{ "check", "--no-cache" }, .roc_file = "test/cli/package_shorthand_check_app/main.roc", .exit = .success, .not_contains = &.{.{ .stream = .stderr, .text = "panic" }} } } },
     .{ .id = 0, .suite = .subcommands, .name = "roc check resolves and checks a used sibling package shorthand (issue 9488)", .body = .{ .command = .{ .args = &.{ "check", "--no-cache" }, .roc_file = "test/cli/package_shorthand_used_app/main.roc", .exit = .not_panic, .contains = &.{ .{ .stream = .stderr, .text = "package_shorthand_used_pkg" }, .{ .stream = .stderr, .text = "TYPE MISMATCH" } }, .not_contains = &.{.{ .stream = .stderr, .text = "panic" }} } } },
     .{ .id = 0, .suite = .subcommands, .name = "roc check does not hang on tag union type alias inside List (issue 9481)", .body = .{ .command = .{ .args = &.{ "check", "--no-cache" }, .roc_file = "test/cli/tag_union_alias_hang.roc", .not_contains = &.{ .{ .stream = .stderr, .text = "panic" }, .{ .stream = .stderr, .text = "Coordinator stuck" }, .{ .stream = .stderr, .text = "Infinite loop" }, .{ .stream = .stderr, .text = "INFINITE TYPE" } } } } },
+    .{ .id = 0, .suite = .subcommands, .name = "roc check succeeds on string interpolation in Try.map_err (issue 9650)", .body = .{ .command = .{ .args = &.{ "check", "--no-cache" }, .roc_file = "test/cli/issue_9650_checked_interpolation_map_err.roc", .exit = .success, .contains_any = &.{.{ .needles = &no_errors_needles }}, .not_contains = &.{ .{ .stream = .stderr, .text = "ordinary method call reached artifact publication" }, .{ .stream = .stderr, .text = "panic" } } } } },
     .{ .id = 0, .suite = .subcommands, .name = "roc check succeeds on Parser type module", .body = .{ .command = .{ .args = &.{ "check", "--no-cache" }, .roc_file = "test/package_simple_parser/Parser.roc", .not_contains = &.{.{ .stream = .stderr, .text = "error" }} } } },
     .{ .id = 0, .suite = .subcommands, .name = "roc check succeeds when block-local associated value captures local value", .body = .{ .command = .{ .args = &.{ "check", "--no-cache" }, .roc_file = "test/cli/block_local_assoc_capture/Test.roc", .exit = .success } } },
     .{ .id = 0, .suite = .subcommands, .name = "roc test runs expects in Parser type module (interpreter)", .backend = .interpreter, .body = .{ .command = .{ .args = &.{ "test", "--opt=interpreter", "--no-cache" }, .roc_file = "test/package_simple_parser/Parser.roc", .contains = &.{ .{ .stream = .stdout, .text = "passed" }, .{ .stream = .stdout, .text = "(7)" } } } } },

test/cli/issue_9650_checked_interpolation_map_err.roc

@@ -0,0 +1,4 @@
+package [f] {}
+
+f : Str -> Try(U64, Str)
+f = |s| Try.map_err(Err("${(s)}"), |_| "")