shuffle error messages in borrowck, and prevent it from spewing too many

also, fix a few minor issues it complains about

src/rustc/middle/borrowck.rs

@@ -498,6 +498,8 @@ enum check_loan_ctxt = @{
     bccx: borrowck_ctxt,
     req_maps: req_maps,
 
+    reported: hashmap<ast::node_id, ()>,
+
     // Keep track of whether we're inside a ctor, so as to
     // allow mutating immutable fields in the same class if
     // we are in a ctor, we track the self id
@@ -525,6 +527,7 @@ fn check_loans(bccx: borrowck_ctxt,
                crate: @ast::crate) {
     let clcx = check_loan_ctxt(@{bccx: bccx,
                                  req_maps: req_maps,
+                                 reported: int_hash(),
                                  mut in_ctor: false,
                                  mut is_pure: pc_impure});
     let vt = visit::mk_vt(@{visit_expr: check_loans_in_expr,
@@ -641,11 +644,9 @@ impl methods for check_loan_ctxt {
                 /*ok*/
               }
               ast::impure_fn | ast::unsafe_fn {
-                self.bccx.span_err(
+                self.report_purity_error(
                     expr.span,
-                    "access to non-pure functions \
-                     prohibited in a pure context");
-                self.report_why_pure();
+                    "access to non-pure functions");
               }
             }
           }
@@ -739,11 +740,9 @@ impl methods for check_loan_ctxt {
         // assigned, because it is uniquely tied to this function and
         // is not visible from the outside
         if self.is_pure != pc_impure && cmt.lp.is_none() {
-            self.bccx.span_err(
+            self.report_purity_error(
                 ex.span,
-                #fmt["%s prohibited in a pure context",
-                     at.ing_form(self.bccx.cmt_to_str(cmt))]);
-            self.report_why_pure();
+                at.ing_form(self.bccx.cmt_to_str(cmt)));
         }
 
         // check for a conflicting loan as well, except in the case of
@@ -776,19 +775,26 @@ impl methods for check_loan_ctxt {
         self.bccx.add_to_mutbl_map(cmt);
     }
 
-    fn report_why_pure() {
-        alt self.is_pure {
+    fn report_purity_error(sp: span, msg: str) {
+        alt copy self.is_pure {
           pc_impure {
-            self.tcx().sess.bug("report_why_pure() called when impure");
+            self.tcx().sess.bug("report_purity_error() called when impure");
           }
           pc_declaration {
-            // fn was declared pure; no need to report this, I think
+            self.tcx().sess.span_err(
+                sp,
+                #fmt["%s prohibited in pure context", msg]);
           }
           pc_cmt(e) {
-            self.tcx().sess.span_note(
-                e.cmt.span,
-                #fmt["pure context is required due to an illegal borrow: %s",
-                     self.bccx.bckerr_code_to_str(e.code)]);
+            if self.reported.insert(e.cmt.id, ()) {
+                self.tcx().sess.span_err(
+                    e.cmt.span,
+                    #fmt["illegal borrow unless pure: %s",
+                         self.bccx.bckerr_code_to_str(e.code)]);
+                self.tcx().sess.span_note(
+                    sp,
+                    #fmt["impure due to %s", msg]);
+            }
           }
         }
     }

src/rustc/middle/resolve.rs

@@ -717,7 +717,7 @@ fn follow_import(e: env, &&sc: scopes, path: [ident], sp: span) ->
     let mut dcur = lookup_in_scope_strict(e, sc, sp, path[0], ns_module);
     let mut i = 1u;
     loop {
-       alt dcur {
+       alt copy dcur {
           some(dcur_def) {
             if i == path_len { break; }
             dcur =
@@ -725,7 +725,7 @@ fn follow_import(e: env, &&sc: scopes, path: [ident], sp: span) ->
                                  ns_module, outside);
             i += 1u;
           }
-          _ { break; }
+          none { break; }
        }
     }
     if i == path_len {

src/rustc/middle/typeck.rs

@@ -235,7 +235,7 @@ fn check_main_fn_ty(ccx: @crate_ctxt,
 fn check_for_main_fn(ccx: @crate_ctxt, crate: @ast::crate) {
     let tcx = ccx.tcx;
     if !tcx.sess.building_library {
-        alt tcx.sess.main_fn {
+        alt copy tcx.sess.main_fn {
           some((id, sp)) { check_main_fn_ty(ccx, id, sp); }
           none { tcx.sess.span_err(crate.span, "main function not found"); }
         }

src/test/compile-fail/borrowck-lend-args.rs

@@ -8,8 +8,8 @@ fn borrow_from_arg_imm_ref(&&v: ~int) {
 }
 
 fn borrow_from_arg_mut_ref(&v: ~int) {
-    borrow(v); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn borrow_from_arg_move(-v: ~int) {

src/test/compile-fail/borrowck-pat-enum-in-box.rs

@@ -30,8 +30,8 @@ fn process(_i: int) {}
 
 fn match_const_box_and_do_bad_things(v: &const @const option<int>) {
     alt *v {
-      @some(i) { //! NOTE pure context is required due to an illegal borrow: enum variant in aliasable, mutable location
-        process(i) //! ERROR access to non-pure functions prohibited in a pure context
+      @some(i) { //! ERROR illegal borrow unless pure: enum variant in aliasable, mutable location
+        process(i) //! NOTE impure due to access to non-pure functions
       }
       @none {}
     }

src/test/compile-fail/borrowck-pat-enum.rs

@@ -36,8 +36,8 @@ fn match_const_reg_unused(v: &const option<int>) {
 
 fn match_const_reg_impure(v: &const option<int>) {
     alt *v {
-      some(i) {impure(i)} //! ERROR access to non-pure functions prohibited in a pure context
-      //!^ NOTE pure context is required due to an illegal borrow: enum variant in aliasable, mutable location
+      some(i) {impure(i)} //! ERROR illegal borrow unless pure: enum variant in aliasable, mutable location
+      //!^ NOTE impure due to access to non-pure functions
       none {}
     }
 }

src/test/compile-fail/borrowck-unchecked-with-borrow.rs

@@ -3,13 +3,13 @@
 
 fn impure(_i: int) {}
 
+// check that unchecked alone does not override borrowck:
 fn foo(v: &const option<int>) {
     alt *v {
       some(i) {
-        //!^ NOTE pure context is required due to an illegal borrow: enum variant in aliasable, mutable location
-        // check that unchecked alone does not override borrowck:
+        //!^ ERROR illegal borrow unless pure: enum variant in aliasable, mutable location
         unchecked {
-            impure(i); //! ERROR access to non-pure functions prohibited in a pure context
+            impure(i); //! NOTE impure due to access to non-pure functions
         }
       }
       none {

src/test/compile-fail/borrowck-uniq-via-box.rs

@@ -4,23 +4,23 @@
 fn borrow(_v: &int) {}
 
 fn box_mut(v: @mut ~int) {
-    borrow(*v); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(*v); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_rec_mut(v: @{mut f: ~int}) {
-    borrow(v.f); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_mut_rec(v: @mut {f: ~int}) {
-    borrow(v.f); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_mut_recs(v: @mut {f: {g: {h: ~int}}}) {
-    borrow(v.f.g.h); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f.g.h); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_imm(v: @~int) {
@@ -36,28 +36,28 @@ fn box_imm_recs(v: @{f: {g: {h: ~int}}}) {
 }
 
 fn box_const(v: @const ~int) {
-    borrow(*v); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(*v); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_rec_const(v: @{const f: ~int}) {
-    borrow(v.f); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_recs_const(v: @{f: {g: {const h: ~int}}}) {
-    borrow(v.f.g.h); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f.g.h); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_const_rec(v: @const {f: ~int}) {
-    borrow(v.f); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_const_recs(v: @const {f: {g: {h: ~int}}}) {
-    borrow(v.f.g.h); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f.g.h); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn main() {

src/test/compile-fail/borrowck-uniq-via-ref.rs

@@ -3,23 +3,23 @@
 fn borrow(_v: &int) {}
 
 fn box_mut(v: &mut ~int) {
-    borrow(*v); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(*v); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_rec_mut(v: &{mut f: ~int}) {
-    borrow(v.f); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_mut_rec(v: &mut {f: ~int}) {
-    borrow(v.f); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_mut_recs(v: &mut {f: {g: {h: ~int}}}) {
-    borrow(v.f.g.h); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f.g.h); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_imm(v: &~int) {
@@ -35,28 +35,28 @@ fn box_imm_recs(v: &{f: {g: {h: ~int}}}) {
 }
 
 fn box_const(v: &const ~int) {
-    borrow(*v); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(*v); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_rec_const(v: &{const f: ~int}) {
-    borrow(v.f); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_recs_const(v: &{f: {g: {const h: ~int}}}) {
-    borrow(v.f.g.h); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f.g.h); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_const_rec(v: &const {f: ~int}) {
-    borrow(v.f); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn box_const_recs(v: &const {f: {g: {h: ~int}}}) {
-    borrow(v.f.g.h); //! ERROR access to non-pure functions prohibited in a pure context
-    //!^ NOTE pure context is required due to an illegal borrow: unique value in aliasable, mutable location
+    borrow(v.f.g.h); //! ERROR illegal borrow unless pure: unique value in aliasable, mutable location
+    //!^ NOTE impure due to access to non-pure functions
 }
 
 fn main() {

src/test/compile-fail/impure-pred.rs

@@ -3,7 +3,7 @@
 fn g() { }
 
 pure fn f(_q: int) -> bool {
-    g(); //! ERROR access to non-pure functions prohibited in a pure context
+    g(); //! ERROR access to non-pure functions prohibited in pure context
     ret true;
 }
 

src/test/compile-fail/pure-modifies-aliased.rs

@@ -1,16 +1,16 @@
 // Check that pure functions cannot modify aliased state.
 
 pure fn modify_in_ref(&&sum: {mut f: int}) {
-    sum.f = 3; //! ERROR assigning to mutable field prohibited in a pure context
+    sum.f = 3; //! ERROR assigning to mutable field prohibited in pure context
 }
 
 pure fn modify_in_box(sum: @mut {f: int}) {
-    sum.f = 3; //! ERROR assigning to mutable field prohibited in a pure context
+    sum.f = 3; //! ERROR assigning to mutable field prohibited in pure context
 }
 
 impl foo for int {
     pure fn modify_in_box_rec(sum: @{mut f: int}) {
-        sum.f = self; //! ERROR assigning to mutable field prohibited in a pure context
+        sum.f = self; //! ERROR assigning to mutable field prohibited in pure context
     }
 }