Fix a translator crash with index expressions.

src/compiler/translator/ParseContext.cpp

@@ -2051,9 +2051,11 @@ TIntermTyped* TParseContext::addIndexExpression(TIntermTyped *baseExpression, co
         recover();
     }
 
-    if (indexExpression->getQualifier() == EvqConst)
+    TIntermConstantUnion *indexConstantUnion = indexExpression->getAsConstantUnion();
+
+    if (indexExpression->getQualifier() == EvqConst && indexConstantUnion)
     {
-        int index = indexExpression->getAsConstantUnion()->getIConst(0);
+        int index = indexConstantUnion->getIConst(0);
         if (index < 0)
         {
             std::stringstream infoStream;
@@ -2114,7 +2116,7 @@ TIntermTyped* TParseContext::addIndexExpression(TIntermTyped *baseExpression, co
                 index = baseExpression->getType().getNominalSize() - 1;
             }
 
-            indexExpression->getAsConstantUnion()->getUnionArrayPointer()->setIConst(index);
+            indexConstantUnion->getUnionArrayPointer()->setIConst(index);
             indexedExpression = intermediate.addIndex(EOpIndexDirect, baseExpression, indexExpression, location);
         }
     }

tests/angle_tests/GLSLTest.cpp

@@ -821,3 +821,56 @@ TYPED_TEST(GLSLTest, ZeroShaderLength)
     glGetShaderiv(shader, GL_COMPILE_STATUS, &compileResult);
     EXPECT_NE(compileResult, 0);
 }
+
+// Tests that bad index expressions don't crash ANGLE's translator.
+// https://code.google.com/p/angleproject/issues/detail?id=857
+TYPED_TEST(GLSLTest, BadIndexBug)
+{
+    const std::string &fragmentShaderSourceVec =
+        "precision mediump float;\n"
+        "uniform vec4 uniformVec;\n"
+        "void main()\n"
+        "{\n"
+        "    gl_FragColor = vec4(uniformVec[int()]);\n"
+        "}";
+
+    GLuint shader = CompileShader(GL_FRAGMENT_SHADER, fragmentShaderSourceVec);
+    EXPECT_EQ(0u, shader);
+
+    if (shader != 0)
+    {
+        glDeleteShader(shader);
+    }
+
+    const std::string &fragmentShaderSourceMat =
+        "precision mediump float;\n"
+        "uniform mat4 uniformMat;\n"
+        "void main()\n"
+        "{\n"
+        "    gl_FragColor = vec4(uniformMat[int()]);\n"
+        "}";
+
+    shader = CompileShader(GL_FRAGMENT_SHADER, fragmentShaderSourceMat);
+    EXPECT_EQ(0u, shader);
+
+    if (shader != 0)
+    {
+        glDeleteShader(shader);
+    }
+
+    const std::string &fragmentShaderSourceArray =
+        "precision mediump float;\n"
+        "uniform vec4 uniformArray;\n"
+        "void main()\n"
+        "{\n"
+        "    gl_FragColor = vec4(uniformArray[int()]);\n"
+        "}";
+
+    shader = CompileShader(GL_FRAGMENT_SHADER, fragmentShaderSourceArray);
+    EXPECT_EQ(0u, shader);
+
+    if (shader != 0)
+    {
+        glDeleteShader(shader);
+    }
+}
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