Fix a compiler abort when generating code for determistic string

Estimated hours taken: 1
Branches: main

compiler/ml_string_switch.m:
	Fix a compiler abort when generating code for determistic string
	switches.

tests/valid/Mmakefile:
tests/valid/det_string_switch.m:
	Add test case.

compiler/ml_string_switch.m

@@ -1,7 +1,7 @@
 %-----------------------------------------------------------------------------%
 % vim: ft=mercury ts=4 sw=4 et
 %-----------------------------------------------------------------------------%
-% Copyright (C) 1994-2006 The University of Melbourne.
+% Copyright (C) 1994-2007 The University of Melbourne.
 % This file may only be copied under the terms of the GNU General
 % Public License - see the file COPYING in the Mercury distribution.
 %-----------------------------------------------------------------------------%
@@ -103,7 +103,21 @@ generate(Cases, Var, CodeModel, _CanFail, Context, Decls, Statements, !Info) :-
     switch_util.calc_hash_slots(HashValsList, HashValsMap, HashSlotsMap),
 
     % Generate the code for when the hash lookup fails.
-    ml_gen_failure(CodeModel, Context, FailStatements, !Info),
+    (
+        CodeModel = model_det,
+        FailComment =
+            statement(ml_stmt_atomic(comment("switch cannot fail")),
+                MLDS_Context),
+        FailStatements = []
+    ;
+        ( CodeModel = model_semi
+        ; CodeModel = model_non
+        ),
+        FailComment =
+            statement(ml_stmt_atomic(comment("no match, so fail")),
+                MLDS_Context),
+        ml_gen_failure(CodeModel, Context, FailStatements, !Info)
+    ),
 
     % Generate the code etc. for the hash table.
     gen_hash_slots(0, TableSize, HashSlotsMap, CodeModel,
@@ -196,9 +210,6 @@ generate(Cases, Var, CodeModel, _CanFail, Context, Decls, Statements, !Info) :-
                 yes), % This is a do...while loop.
             MLDS_Context)
         ],
-    FailComment =
-        statement(ml_stmt_atomic(comment("no match, so fail")),
-            MLDS_Context),
     EndLabelStatement = statement(ml_stmt_label(EndLabel), MLDS_Context),
     EndComment =
         statement(ml_stmt_atomic(comment("end of hashed string switch")),

tests/valid/Mmakefile

@@ -75,6 +75,7 @@ OTHER_PROGS= \
 	deforest_rerun_det \
 	det_condition \
 	det_inference \
+	det_string_switch \
 	det_switch \
 	double_vn \
 	easy_nondet_test \

tests/valid/det_string_switch.m

@@ -0,0 +1,34 @@
+% This is a regression test for a bug in MLDS code generation where it would
+% abort while generating the code of a deterministic string switch.
+%
+% Uncaught Mercury exception:
+% Software Error: ml_code_util.m: Unexpected: ml_gen_failure: `fail' has determinism `det'
+
+:- module det_string_switch.
+:- interface.
+
+:- import_module io.
+
+% Need this many cases to make a string switch.
+:- inst bar
+    --->    "a"
+    ;       "b"
+    ;       "c"
+    ;       "d"
+    ;       "e"
+    ;       "f"
+    ;       "g"
+    ;       "h".
+
+:- pred foo(string::in(bar), io::di, io::uo) is det.
+
+:- implementation.
+
+foo("a", !IO).
+foo("b", !IO).
+foo("c", !IO).
+foo("d", !IO). 
+foo("e", !IO).
+foo("f", !IO).
+foo("g", !IO).
+foo("h", !IO).