From 5c8069d817d5be3dc577dce6ab59ebfd89d19843 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Wed, 16 May 2012 06:38:43 -0700
Subject: [PATCH] break out type checking of alts/patterns (again)

---
 src/rustc/middle/typeck/check.rs     | 262 +-------------------------
 src/rustc/middle/typeck/check/alt.rs | 267 +++++++++++++++++++++++++++
 src/rustc/rustc.rc                   |   4 +-
 3 files changed, 272 insertions(+), 261 deletions(-)
 create mode 100644 src/rustc/middle/typeck/check/alt.rs

diff --git a/src/rustc/middle/typeck/check.rs b/src/rustc/middle/typeck/check.rs
index 620a353617c8..2d41a86f9ddb 100644
--- a/src/rustc/middle/typeck/check.rs
+++ b/src/rustc/middle/typeck/check.rs
@@ -559,15 +559,6 @@ fn valid_range_bounds(ccx: @crate_ctxt, from: @ast::expr, to: @ast::expr)
     const_eval::compare_lit_exprs(ccx.tcx, from, to) <= 0
 }
 
-type pat_ctxt = {
-    fcx: @fn_ctxt,
-    map: pat_id_map,
-    alt_region: ty::region,
-    block_region: ty::region,
-    /* Equal to either alt_region or block_region. */
-    pat_region: ty::region
-};
-
 // Helper for the other universally_quantify_*() routines.  Extracts the bound
 // regions from bound_tys and then replaces those same regions with fresh
 // variables in `sty`, returning the resulting type.
@@ -673,223 +664,6 @@ fn replace_bound_regions(
     }
 }
 
-fn check_pat_variant(pcx: pat_ctxt, pat: @ast::pat, path: @ast::path,
-                     subpats: option<[@ast::pat]>, expected: ty::t) {
-
-    // Typecheck the path.
-    let fcx = pcx.fcx;
-    let tcx = pcx.fcx.ccx.tcx;
-
-    // Lookup the enum and variant def ids:
-    let v_def = lookup_def(pcx.fcx, path.span, pat.id);
-    let v_def_ids = ast_util::variant_def_ids(v_def);
-
-    // Assign the pattern the type of the *enum*, not the variant.
-    let enum_tpt = ty::lookup_item_type(tcx, v_def_ids.enm);
-    instantiate_path(pcx.fcx, path, enum_tpt, pat.span, pat.id);
-
-    // Take the enum type params out of `expected`.
-    alt structure_of(pcx.fcx, pat.span, expected) {
-      ty::ty_enum(_, expected_substs) {
-        // check that the type of the value being matched is a subtype
-        // of the type of the pattern:
-        let pat_ty = fcx.node_ty(pat.id);
-        demand::suptype(fcx, pat.span, pat_ty, expected);
-
-        // Get the expected types of the arguments.
-        let arg_types = {
-            let vinfo =
-                ty::enum_variant_with_id(
-                    tcx, v_def_ids.enm, v_def_ids.var);
-            vinfo.args.map { |t| ty::subst(tcx, expected_substs, t) }
-        };
-        let arg_len = arg_types.len(), subpats_len = alt subpats {
-            none { arg_len }
-            some(ps) { ps.len() }};
-        if arg_len > 0u {
-            // N-ary variant.
-            if arg_len != subpats_len {
-                let s = #fmt["this pattern has %u field%s, but the \
-                              corresponding variant has %u field%s",
-                             subpats_len,
-                             if subpats_len == 1u { "" } else { "s" },
-                             arg_len,
-                             if arg_len == 1u { "" } else { "s" }];
-                tcx.sess.span_fatal(pat.span, s);
-            }
-
-            option::iter(subpats) {|pats|
-                vec::iter2(pats, arg_types) {|subpat, arg_ty|
-                  check_pat(pcx, subpat, arg_ty);
-                }
-            };
-        } else if subpats_len > 0u {
-            tcx.sess.span_fatal
-                (pat.span, #fmt["this pattern has %u field%s, \
-                                 but the corresponding variant has no fields",
-                                subpats_len,
-                                if subpats_len == 1u { "" }
-                                else { "s" }]);
-        }
-      }
-      _ {
-        tcx.sess.span_fatal
-            (pat.span,
-             #fmt["mismatched types: expected enum but found `%s`",
-                  fcx.ty_to_str(expected)]);
-      }
-    }
-}
-
-// Pattern checking is top-down rather than bottom-up so that bindings get
-// their types immediately.
-fn check_pat(pcx: pat_ctxt, pat: @ast::pat, expected: ty::t) {
-    let fcx = pcx.fcx;
-    let tcx = pcx.fcx.ccx.tcx;
-    alt pat.node {
-      ast::pat_wild {
-        fcx.write_ty(pat.id, expected);
-      }
-      ast::pat_lit(lt) {
-        check_expr_with(pcx.fcx, lt, expected);
-        fcx.write_ty(pat.id, fcx.expr_ty(lt));
-      }
-      ast::pat_range(begin, end) {
-        check_expr_with(pcx.fcx, begin, expected);
-        check_expr_with(pcx.fcx, end, expected);
-        let b_ty = resolve_type_vars_if_possible(pcx.fcx,
-                                                 fcx.expr_ty(begin));
-        if !require_same_types(
-            tcx, pat.span, b_ty,
-            resolve_type_vars_if_possible(
-                pcx.fcx, fcx.expr_ty(end)),
-            {|| "mismatched types in range" }) {
-            // no-op
-        } else if !ty::type_is_numeric(b_ty) {
-            tcx.sess.span_err(pat.span, "non-numeric type used in range");
-        } else if !valid_range_bounds(pcx.fcx.ccx, begin, end) {
-            tcx.sess.span_err(begin.span, "lower range bound must be less \
-                                           than upper");
-        }
-        fcx.write_ty(pat.id, b_ty);
-      }
-      ast::pat_ident(name, sub) if !pat_is_variant(tcx.def_map, pat) {
-        let vid = lookup_local(pcx.fcx, pat.span, pat.id);
-        let mut typ = ty::mk_var(tcx, vid);
-        demand::suptype(pcx.fcx, pat.span, expected, typ);
-        let canon_id = pcx.map.get(pat_util::path_to_ident(name));
-        if canon_id != pat.id {
-            let tv_id = lookup_local(pcx.fcx, pat.span, canon_id);
-            let ct = ty::mk_var(tcx, tv_id);
-            demand::suptype(pcx.fcx, pat.span, ct, typ);
-        }
-        fcx.write_ty(pat.id, typ);
-        alt sub {
-          some(p) { check_pat(pcx, p, expected); }
-          _ {}
-        }
-      }
-      ast::pat_ident(path, c) {
-        check_pat_variant(pcx, pat, path, some([]), expected);
-      }
-      ast::pat_enum(path, subpats) {
-        check_pat_variant(pcx, pat, path, subpats, expected);
-      }
-      ast::pat_rec(fields, etc) {
-        let ex_fields = alt structure_of(pcx.fcx, pat.span, expected) {
-          ty::ty_rec(fields) { fields }
-          _ {
-            tcx.sess.span_fatal
-                (pat.span,
-                #fmt["mismatched types: expected `%s` but found record",
-                     fcx.ty_to_str(expected)]);
-          }
-        };
-        let f_count = vec::len(fields);
-        let ex_f_count = vec::len(ex_fields);
-        if ex_f_count < f_count || !etc && ex_f_count > f_count {
-            tcx.sess.span_fatal
-                (pat.span, #fmt["mismatched types: expected a record \
-                      with %u fields, found one with %u \
-                      fields",
-                                ex_f_count, f_count]);
-        }
-        fn matches(name: str, f: ty::field) -> bool {
-            ret str::eq(name, f.ident);
-        }
-        for fields.each {|f|
-            alt vec::find(ex_fields, bind matches(f.ident, _)) {
-              some(field) {
-                check_pat(pcx, f.pat, field.mt.ty);
-              }
-              none {
-                tcx.sess.span_fatal(pat.span,
-                                    #fmt["mismatched types: did not \
-                                          expect a record with a field `%s`",
-                                         f.ident]);
-              }
-            }
-        }
-        fcx.write_ty(pat.id, expected);
-      }
-      ast::pat_tup(elts) {
-        let ex_elts = alt structure_of(pcx.fcx, pat.span, expected) {
-          ty::ty_tup(elts) { elts }
-          _ {
-            tcx.sess.span_fatal
-                (pat.span,
-                 #fmt["mismatched types: expected `%s`, found tuple",
-                      fcx.ty_to_str(expected)]);
-          }
-        };
-        let e_count = vec::len(elts);
-        if e_count != vec::len(ex_elts) {
-            tcx.sess.span_fatal
-                (pat.span, #fmt["mismatched types: expected a tuple \
-                      with %u fields, found one with %u \
-                      fields", vec::len(ex_elts), e_count]);
-        }
-        let mut i = 0u;
-        for elts.each {|elt|
-            check_pat(pcx, elt, ex_elts[i]);
-            i += 1u;
-        }
-
-        fcx.write_ty(pat.id, expected);
-      }
-      ast::pat_box(inner) {
-        alt structure_of(pcx.fcx, pat.span, expected) {
-          ty::ty_box(e_inner) {
-            check_pat(pcx, inner, e_inner.ty);
-            fcx.write_ty(pat.id, expected);
-          }
-          _ {
-            tcx.sess.span_fatal(
-                pat.span,
-                "mismatched types: expected `" +
-                pcx.fcx.ty_to_str(expected) +
-                "` found box");
-          }
-        }
-      }
-      ast::pat_uniq(inner) {
-        alt structure_of(pcx.fcx, pat.span, expected) {
-          ty::ty_uniq(e_inner) {
-            check_pat(pcx, inner, e_inner.ty);
-            fcx.write_ty(pat.id, expected);
-          }
-          _ {
-            tcx.sess.span_fatal(
-                pat.span,
-                "mismatched types: expected `" +
-                pcx.fcx.ty_to_str(expected) +
-                "` found uniq");
-          }
-        }
-      }
-    }
-}
-
 fn check_expr_with(fcx: @fn_ctxt, expr: @ast::expr, expected: ty::t) -> bool {
     check_expr(fcx, expr, some(expected))
 }
@@ -1870,38 +1644,7 @@ fn check_expr_with_unifier(fcx: @fn_ctxt,
           bot = !may_break(body);
       }
       ast::expr_alt(discrim, arms, _) {
-        let pattern_ty = fcx.next_ty_var();
-        bot = check_expr_with(fcx, discrim, pattern_ty);
-
-        // Typecheck the patterns first, so that we get types for all the
-        // bindings.
-        //let pattern_ty = fcx.expr_ty(discrim);
-        for arms.each {|arm|
-            let pcx = {
-                fcx: fcx,
-                map: pat_id_map(tcx.def_map, arm.pats[0]),
-                alt_region: ty::re_scope(expr.id),
-                block_region: ty::re_scope(arm.body.node.id),
-                pat_region: ty::re_scope(expr.id)
-            };
-
-            for arm.pats.each {|p| check_pat(pcx, p, pattern_ty);}
-        }
-        // Now typecheck the blocks.
-        let mut result_ty = fcx.next_ty_var();
-        let mut arm_non_bot = false;
-        for arms.each {|arm|
-            alt arm.guard {
-              some(e) { check_expr_with(fcx, e, ty::mk_bool(tcx)); }
-              none { }
-            }
-            if !check_block(fcx, arm.body) { arm_non_bot = true; }
-            let bty = fcx.node_ty(arm.body.node.id);
-            demand::suptype(fcx, arm.body.span, result_ty, bty);
-        }
-        bot |= !arm_non_bot;
-        if !arm_non_bot { result_ty = ty::mk_bot(tcx); }
-        fcx.write_ty(id, result_ty);
+        bot = alt::check_alt(fcx, expr, discrim, arms);
       }
       ast::expr_fn(proto, decl, body, cap_clause) {
         check_expr_fn(fcx, expr, proto, decl, body, false, expected);
@@ -2344,8 +2087,7 @@ fn check_decl_local(fcx: @fn_ctxt, local: @ast::local) -> bool {
         block_region: region,
         pat_region: region
     };
-
-    check_pat(pcx, local.node.pat, t);
+    alt::check_pat(pcx, local.node.pat, t);
     ret bot;
 }
 
diff --git a/src/rustc/middle/typeck/check/alt.rs b/src/rustc/middle/typeck/check/alt.rs
new file mode 100644
index 000000000000..ef9c574ccd20
--- /dev/null
+++ b/src/rustc/middle/typeck/check/alt.rs
@@ -0,0 +1,267 @@
+fn check_alt(fcx: @fn_ctxt,
+             expr: @ast::expr,
+             discrim: @ast::expr,
+             arms: [ast::arm]) -> bool {
+    let tcx = fcx.ccx.tcx;
+    let mut bot = false;
+
+    let pattern_ty = fcx.next_ty_var();
+    bot = check_expr_with(fcx, discrim, pattern_ty);
+
+    // Typecheck the patterns first, so that we get types for all the
+    // bindings.
+    for arms.each {|arm|
+        let pcx = {
+            fcx: fcx,
+            map: pat_id_map(tcx.def_map, arm.pats[0]),
+            alt_region: ty::re_scope(expr.id),
+            block_region: ty::re_scope(arm.body.node.id),
+            pat_region: ty::re_scope(expr.id)
+        };
+
+        for arm.pats.each {|p| check_pat(pcx, p, pattern_ty);}
+    }
+    // Now typecheck the blocks.
+    let mut result_ty = fcx.next_ty_var();
+    let mut arm_non_bot = false;
+    for arms.each {|arm|
+        alt arm.guard {
+          some(e) { check_expr_with(fcx, e, ty::mk_bool(tcx)); }
+          none { }
+        }
+        if !check_block(fcx, arm.body) { arm_non_bot = true; }
+        let bty = fcx.node_ty(arm.body.node.id);
+        demand::suptype(fcx, arm.body.span, result_ty, bty);
+    }
+    bot |= !arm_non_bot;
+    if !arm_non_bot { result_ty = ty::mk_bot(tcx); }
+    fcx.write_ty(expr.id, result_ty);
+    ret bot;
+}
+
+type pat_ctxt = {
+    fcx: @fn_ctxt,
+    map: pat_id_map,
+    alt_region: ty::region,
+    block_region: ty::region,
+    /* Equal to either alt_region or block_region. */
+    pat_region: ty::region
+};
+
+fn check_pat_variant(pcx: pat_ctxt, pat: @ast::pat, path: @ast::path,
+                     subpats: option<[@ast::pat]>, expected: ty::t) {
+
+    // Typecheck the path.
+    let fcx = pcx.fcx;
+    let tcx = pcx.fcx.ccx.tcx;
+
+    // Lookup the enum and variant def ids:
+    let v_def = lookup_def(pcx.fcx, path.span, pat.id);
+    let v_def_ids = ast_util::variant_def_ids(v_def);
+
+    // Assign the pattern the type of the *enum*, not the variant.
+    let enum_tpt = ty::lookup_item_type(tcx, v_def_ids.enm);
+    instantiate_path(pcx.fcx, path, enum_tpt, pat.span, pat.id);
+
+    // Take the enum type params out of `expected`.
+    alt structure_of(pcx.fcx, pat.span, expected) {
+      ty::ty_enum(_, expected_substs) {
+        // check that the type of the value being matched is a subtype
+        // of the type of the pattern:
+        let pat_ty = fcx.node_ty(pat.id);
+        demand::suptype(fcx, pat.span, pat_ty, expected);
+
+        // Get the expected types of the arguments.
+        let arg_types = {
+            let vinfo =
+                ty::enum_variant_with_id(
+                    tcx, v_def_ids.enm, v_def_ids.var);
+            vinfo.args.map { |t| ty::subst(tcx, expected_substs, t) }
+        };
+        let arg_len = arg_types.len(), subpats_len = alt subpats {
+            none { arg_len }
+            some(ps) { ps.len() }};
+        if arg_len > 0u {
+            // N-ary variant.
+            if arg_len != subpats_len {
+                let s = #fmt["this pattern has %u field%s, but the \
+                              corresponding variant has %u field%s",
+                             subpats_len,
+                             if subpats_len == 1u { "" } else { "s" },
+                             arg_len,
+                             if arg_len == 1u { "" } else { "s" }];
+                tcx.sess.span_fatal(pat.span, s);
+            }
+
+            option::iter(subpats) {|pats|
+                vec::iter2(pats, arg_types) {|subpat, arg_ty|
+                  check_pat(pcx, subpat, arg_ty);
+                }
+            };
+        } else if subpats_len > 0u {
+            tcx.sess.span_fatal
+                (pat.span, #fmt["this pattern has %u field%s, \
+                                 but the corresponding variant has no fields",
+                                subpats_len,
+                                if subpats_len == 1u { "" }
+                                else { "s" }]);
+        }
+      }
+      _ {
+        tcx.sess.span_fatal
+            (pat.span,
+             #fmt["mismatched types: expected enum but found `%s`",
+                  fcx.ty_to_str(expected)]);
+      }
+    }
+}
+
+// Pattern checking is top-down rather than bottom-up so that bindings get
+// their types immediately.
+fn check_pat(pcx: pat_ctxt, pat: @ast::pat, expected: ty::t) {
+    let fcx = pcx.fcx;
+    let tcx = pcx.fcx.ccx.tcx;
+    alt pat.node {
+      ast::pat_wild {
+        fcx.write_ty(pat.id, expected);
+      }
+      ast::pat_lit(lt) {
+        check_expr_with(pcx.fcx, lt, expected);
+        fcx.write_ty(pat.id, fcx.expr_ty(lt));
+      }
+      ast::pat_range(begin, end) {
+        check_expr_with(pcx.fcx, begin, expected);
+        check_expr_with(pcx.fcx, end, expected);
+        let b_ty = resolve_type_vars_if_possible(pcx.fcx,
+                                                 fcx.expr_ty(begin));
+        if !require_same_types(
+            tcx, pat.span, b_ty,
+            resolve_type_vars_if_possible(
+                pcx.fcx, fcx.expr_ty(end)),
+            {|| "mismatched types in range" }) {
+            // no-op
+        } else if !ty::type_is_numeric(b_ty) {
+            tcx.sess.span_err(pat.span, "non-numeric type used in range");
+        } else if !valid_range_bounds(pcx.fcx.ccx, begin, end) {
+            tcx.sess.span_err(begin.span, "lower range bound must be less \
+                                           than upper");
+        }
+        fcx.write_ty(pat.id, b_ty);
+      }
+      ast::pat_ident(name, sub) if !pat_is_variant(tcx.def_map, pat) {
+        let vid = lookup_local(pcx.fcx, pat.span, pat.id);
+        let mut typ = ty::mk_var(tcx, vid);
+        demand::suptype(pcx.fcx, pat.span, expected, typ);
+        let canon_id = pcx.map.get(pat_util::path_to_ident(name));
+        if canon_id != pat.id {
+            let tv_id = lookup_local(pcx.fcx, pat.span, canon_id);
+            let ct = ty::mk_var(tcx, tv_id);
+            demand::suptype(pcx.fcx, pat.span, ct, typ);
+        }
+        fcx.write_ty(pat.id, typ);
+        alt sub {
+          some(p) { check_pat(pcx, p, expected); }
+          _ {}
+        }
+      }
+      ast::pat_ident(path, c) {
+        check_pat_variant(pcx, pat, path, some([]), expected);
+      }
+      ast::pat_enum(path, subpats) {
+        check_pat_variant(pcx, pat, path, subpats, expected);
+      }
+      ast::pat_rec(fields, etc) {
+        let ex_fields = alt structure_of(pcx.fcx, pat.span, expected) {
+          ty::ty_rec(fields) { fields }
+          _ {
+            tcx.sess.span_fatal
+                (pat.span,
+                #fmt["mismatched types: expected `%s` but found record",
+                     fcx.ty_to_str(expected)]);
+          }
+        };
+        let f_count = vec::len(fields);
+        let ex_f_count = vec::len(ex_fields);
+        if ex_f_count < f_count || !etc && ex_f_count > f_count {
+            tcx.sess.span_fatal
+                (pat.span, #fmt["mismatched types: expected a record \
+                      with %u fields, found one with %u \
+                      fields",
+                                ex_f_count, f_count]);
+        }
+        fn matches(name: str, f: ty::field) -> bool {
+            ret str::eq(name, f.ident);
+        }
+        for fields.each {|f|
+            alt vec::find(ex_fields, bind matches(f.ident, _)) {
+              some(field) {
+                check_pat(pcx, f.pat, field.mt.ty);
+              }
+              none {
+                tcx.sess.span_fatal(pat.span,
+                                    #fmt["mismatched types: did not \
+                                          expect a record with a field `%s`",
+                                         f.ident]);
+              }
+            }
+        }
+        fcx.write_ty(pat.id, expected);
+      }
+      ast::pat_tup(elts) {
+        let ex_elts = alt structure_of(pcx.fcx, pat.span, expected) {
+          ty::ty_tup(elts) { elts }
+          _ {
+            tcx.sess.span_fatal
+                (pat.span,
+                 #fmt["mismatched types: expected `%s`, found tuple",
+                      fcx.ty_to_str(expected)]);
+          }
+        };
+        let e_count = vec::len(elts);
+        if e_count != vec::len(ex_elts) {
+            tcx.sess.span_fatal
+                (pat.span, #fmt["mismatched types: expected a tuple \
+                      with %u fields, found one with %u \
+                      fields", vec::len(ex_elts), e_count]);
+        }
+        let mut i = 0u;
+        for elts.each {|elt|
+            check_pat(pcx, elt, ex_elts[i]);
+            i += 1u;
+        }
+
+        fcx.write_ty(pat.id, expected);
+      }
+      ast::pat_box(inner) {
+        alt structure_of(pcx.fcx, pat.span, expected) {
+          ty::ty_box(e_inner) {
+            check_pat(pcx, inner, e_inner.ty);
+            fcx.write_ty(pat.id, expected);
+          }
+          _ {
+            tcx.sess.span_fatal(
+                pat.span,
+                "mismatched types: expected `" +
+                pcx.fcx.ty_to_str(expected) +
+                "` found box");
+          }
+        }
+      }
+      ast::pat_uniq(inner) {
+        alt structure_of(pcx.fcx, pat.span, expected) {
+          ty::ty_uniq(e_inner) {
+            check_pat(pcx, inner, e_inner.ty);
+            fcx.write_ty(pat.id, expected);
+          }
+          _ {
+            tcx.sess.span_fatal(
+                pat.span,
+                "mismatched types: expected `" +
+                pcx.fcx.ty_to_str(expected) +
+                "` found uniq");
+          }
+        }
+      }
+    }
+}
+
diff --git a/src/rustc/rustc.rc b/src/rustc/rustc.rc
index 0fffb21c488d..f54907fa63d3 100644
--- a/src/rustc/rustc.rc
+++ b/src/rustc/rustc.rc
@@ -52,7 +52,9 @@ mod middle {
     mod ast_map;
     mod resolve;
     mod typeck {
-        mod check;
+        mod check {
+            mod alt;
+        }
         mod regionck;
         mod demand;
         mod infer;