Make error message on 'my int $a is default(42)' etc. more friendly

rakudo · Aug 27, 2013 · 3bdc0c3 · 3bdc0c3
1 parent 17b17a4
commit 3bdc0c3
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Showing 2 changed files with 43 additions and 16 deletions.
diff --git a/src/core/Exception.pm b/src/core/Exception.pm
@@ -462,6 +462,17 @@ my class X::Trait::Unknown is Exception {
 }
 my class X::Comp::Trait::Unknown is X::Trait::Unknown does X::Comp { };
 
+my class X::Trait::NotOnNative is Exception {
+    has $.type;       # is, will, of etc.
+    has $.subtype;    # wrong subtype being tried
+    has $.native;     # type of native (optional)
+    method message () {
+        "Can't use trait '$.type $.subtype' on a native"
+          ~ ( $.native ?? " $.native." !! "." );
+    }
+}
+my class X::Comp::Trait::NotOnNative is X::Trait::NotOnNative does X::Comp { };
+
 my class X::OutOfRange is Exception {
     has $.what = 'Argument';
     has $.got = '<unknown>';

diff --git a/src/core/Variable.pm b/src/core/Variable.pm
@@ -1,6 +1,7 @@
 # for our tantrums
 my class X::Comp::NYI { ... };
 my class X::Comp::Trait::Unknown { ... };
+my class X::Comp::Trait::NotOnNative { ... };
 
 # Variable traits come here, not in traits.pm, since we declare Variable
 # in the setting rather than BOOTSTRAP.
@@ -13,7 +14,7 @@ my class Variable {
     has $.slash;
 
     # make throwing easier
-    submethod throw ( |c ) {
+    submethod throw ( |c ) is hidden_from_backtrace {
         $*W.throw( self.slash, |c );
     }
 }
@@ -35,23 +36,33 @@ multi trait_mod:<is>(Variable:D $v, Mu:U $is ) {
 multi trait_mod:<is>(Variable:D $v, :$default!) {
     my $var  := $v.var;
     my $what := $var.VAR.WHAT;
-    nqp::getattr(
-      $var,
-      $what.HOW.mixin_base($what),
-      '$!descriptor',
-    ).set_default(nqp::decont($default));
+    try { nqp::getattr(
+            $var,
+            $what.HOW.mixin_base($what),
+            '$!descriptor',
+          ).set_default(nqp::decont($default));
+        CATCH {
+            $v.throw( 'X::Comp::Trait::NotOnNative',
+              :type<is>, :subtype<default> ); # can't find out native type yet
+        }
+    }
 
     # make sure we start with the default if a scalar
     $var = $default if nqp::istype($what, Scalar);
 }
 multi trait_mod:<is>(Variable:D $v, :$dynamic!) {
     my $var  := $v.var;
     my $what := $var.VAR.WHAT;
-    nqp::getattr(
-      $var,
-      $what.HOW.mixin_base($what),
-      '$!descriptor',
-    ).set_dynamic($dynamic);
+    try { nqp::getattr(
+            $var,
+            $what.HOW.mixin_base($what),
+            '$!descriptor',
+          ).set_dynamic($dynamic);
+        CATCH {
+            $v.throw( 'X::Comp::Trait::NotOnNative',
+              :type<is>, :subtype<dynamic> ); # can't find out native type yet
+        }
+    }
 }
 
 # "of" traits
@@ -67,11 +78,16 @@ multi trait_mod:<of>(Variable:D $v, Mu:U $of ) {
     my $var  := $v.var;
     my $what := $var.VAR.WHAT;
     my $how  := $what.HOW;
-    nqp::getattr(
-        $var,
-        $how.mixin_base($what),
-        '$!descriptor'
-    ).set_of(nqp::decont($of));
+    try { nqp::getattr(
+            $var,
+            $how.mixin_base($what),
+            '$!descriptor'
+          ).set_of(nqp::decont($of));
+        CATCH {
+            $v.throw( 'X::Comp::Trait::NotOnNative',
+              :type<of>, :subtype($of.HOW.name($of)) ); # can't find out native type yet
+        }
+    }
     # probably can go if we have a COMPOSE phaser for PARAMETERIZE
     $how.set_name($what,"{$how.name($what)}[{$of.HOW.name($of)}]");
 }