rustdoc: fix inserting source code spans for constant values

This will go wrong when the constants partially result from macro expansion.
Instead, use the expressions and pretty-print them as Rust code.

Fixes: #33302

src/librustdoc/clean/inline.rs

@@ -20,6 +20,7 @@
 use rustc::middle::cstore::{self, CrateStore};
 use rustc::hir::def::Def;
 use rustc::hir::def_id::DefId;
+use rustc::hir::print as pprust;
 use rustc::ty::{self, TyCtxt};
 use rustc::ty::subst;
 use rustc::middle::stability;
@@ -30,7 +31,7 @@
 use doctree;
 use clean::{self, GetDefId};
 
-use super::{Clean, ToSource};
+use super::Clean;
 
 /// Attempt to inline the definition of a local node id into this AST.
 ///
@@ -333,8 +334,8 @@ pub fn build_impl(cx: &DocContext,
                 let did = assoc_const.def_id;
                 let type_scheme = tcx.lookup_item_type(did);
                 let default = if assoc_const.has_value {
-                    Some(lookup_const_by_id(tcx, did, None)
-                         .unwrap().0.span.to_src(cx))
+                    Some(pprust::expr_to_string(
+                        lookup_const_by_id(tcx, did, None).unwrap().0))
                 } else {
                     None
                 };
@@ -479,8 +480,6 @@ fn fill_in(cx: &DocContext, tcx: &TyCtxt, did: DefId,
 
 fn build_const(cx: &DocContext, tcx: &TyCtxt,
                did: DefId) -> clean::Constant {
-    use rustc::hir::print as pprust;
-
     let (expr, ty) = lookup_const_by_id(tcx, did, None).unwrap_or_else(|| {
         panic!("expected lookup_const_by_id to succeed for {:?}", did);
     });

src/librustdoc/clean/mod.rs

@@ -39,6 +39,7 @@
 use rustc::middle::privacy::AccessLevels;
 use rustc::hir::def::Def;
 use rustc::hir::def_id::{DefId, DefIndex, CRATE_DEF_INDEX};
+use rustc::hir::print as pprust;
 use rustc::ty::subst::{self, ParamSpace, VecPerParamSpace};
 use rustc::ty;
 use rustc::middle::stability;
@@ -1285,8 +1286,7 @@ fn clean(&self, cx: &DocContext) -> Item {
         let inner = match self.node {
             hir::ConstTraitItem(ref ty, ref default) => {
                 AssociatedConstItem(ty.clean(cx),
-                                    default.as_ref().map(|expr|
-                                                         expr.span.to_src(cx)))
+                                    default.as_ref().map(|e| pprust::expr_to_string(&e)))
             }
             hir::MethodTraitItem(ref sig, Some(_)) => {
                 MethodItem(sig.clean(cx))
@@ -1316,7 +1316,7 @@ fn clean(&self, cx: &DocContext) -> Item {
         let inner = match self.node {
             hir::ImplItemKind::Const(ref ty, ref expr) => {
                 AssociatedConstItem(ty.clean(cx),
-                                    Some(expr.span.to_src(cx)))
+                                    Some(pprust::expr_to_string(expr)))
             }
             hir::ImplItemKind::Method(ref sig, _) => {
                 MethodItem(sig.clean(cx))
@@ -1635,8 +1635,8 @@ fn clean(&self, cx: &DocContext) -> Type {
                 BorrowedRef {lifetime: l.clean(cx), mutability: m.mutbl.clean(cx),
                              type_: box m.ty.clean(cx)},
             TyVec(ref ty) => Vector(box ty.clean(cx)),
-            TyFixedLengthVec(ref ty, ref e) => FixedVector(box ty.clean(cx),
-                                                           e.span.to_src(cx)),
+            TyFixedLengthVec(ref ty, ref e) =>
+                FixedVector(box ty.clean(cx), pprust::expr_to_string(e)),
             TyTup(ref tys) => Tuple(tys.clean(cx)),
             TyPath(None, ref p) => {
                 resolve_type(cx, p.clean(cx), self.id)
@@ -2185,7 +2185,7 @@ fn clean(&self, cx: &DocContext) -> Item {
             inner: StaticItem(Static {
                 type_: self.type_.clean(cx),
                 mutability: self.mutability.clean(cx),
-                expr: self.expr.span.to_src(cx),
+                expr: pprust::expr_to_string(&self.expr),
             }),
         }
     }
@@ -2209,7 +2209,7 @@ fn clean(&self, cx: &DocContext) -> Item {
             deprecation: self.depr.clean(cx),
             inner: ConstantItem(Constant {
                 type_: self.type_.clean(cx),
-                expr: self.expr.span.to_src(cx),
+                expr: pprust::expr_to_string(&self.expr),
             }),
         }
     }

src/test/rustdoc/issue-33302.rs

+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Ensure constant and array length values are not taken from source
+// code, which wreaks havoc with macros.
+
+#![feature(associated_consts)]
+
+macro_rules! make {
+    ($n:expr) => {
+        pub struct S;
+
+        // @has issue_33302/constant.CST.html \
+        //        '//pre[@class="rust const"]' 'pub const CST: i32 = 4 * 4'
+        pub const CST: i32 = ($n * $n);
+        // @has issue_33302/static.ST.html \
+        //        '//pre[@class="rust static"]' 'pub static ST: i32 = 4 * 4'
+        pub static ST: i32 = ($n * $n);
+
+        pub trait T<X> {
+            fn ignore(_: &X) {}
+            const C: X;
+            // @has issue_33302/trait.T.html \
+            //        '//*[@class="rust trait"]' 'const D: i32 = 4 * 4;'
+            // @has - '//*[@id="associatedconstant.D"]' 'const D: i32 = 4 * 4'
+            const D: i32 = ($n * $n);
+        }
+
+        // @has issue_33302/struct.S.html \
+        //        '//h3[@class="impl"]' 'impl T<[i32; 4 * 4]> for S'
+        // @has - '//*[@id="associatedconstant.C"]' 'const C: [i32; 4 * 4] = [0; 4 * 4]'
+        // @has - '//*[@id="associatedconstant.D"]' 'const D: i32 = 4 * 4'
+        impl T<[i32; ($n * $n)]> for S {
+            const C: [i32; ($n * $n)] = [0; ($n * $n)];
+        }
+    }
+}
+
+make!(4);